These webpages are a collection of hypomnemata (ὑπομνήματα) written out of a personal interest in philosophy and by serendipitously gathering discoveries like the Peregrinaggio di tre giovani figliuoli del re di Serendippo. So let us embark on a journey over the oceans of philosophy, guided by stars of knowledge and the sails of curiosity.

Philosophies traditionally start with a metaphysics: a theory of the essence of things (the ultimate truth or nature of reality), of the fundamental principles that organize the universe (cosmology). Metaphysics ("meta ta phusika": "after the physics") is supposed to answer the question "What is the nature of reality?" Metaphysics is divided into two main categories or divisions. They include ontology (basic categories of being and how they relate to each other) and cosmology (the study of the totality of all phenomena within the universe).
The word ontology comes from the Greek word "ontolos;" which is a participle of the Greek verb "eimi." It means "being" or "existence" and deals with the nature of one's being or existence. An ontology as such is a specification of a conceptualization.
Cosmology is the subdivision of metaphysics that deals with the nature of nature. The term "cosmology" comes from the Greek word "kosmos." It means "order" and generally refers to the world and the universe. Cosmos is antithetical to the concept of chaos. Any philosophical theory also has to deal with the concept of difference and identity. Identity is the relation each thing bears just to itself (sameness), while difference deals with the process or set of properties by which one entity is distinguished from another
(see also Treatise on Basic Philosophy, Vol. 1-8, M. Bunge, Springer, 1974-1985 and Metaphysics, D. W. Hamlyn, Cambridge University Press, 1984 and Theory and Applications of Ontology: Philosophical Perspectives, R. Poli, J. Seibt, Springer, 2010 and Cosmology: The Science of the Universe, E. Harrison, Cambridge University Press, 2000).

Another element of philosophy is philosophy of mind, psychology or cognitive science which also deals with the mind-body problem. Psychology is also a word that comes from the Greek language. It refers to the nature of the psyche (psūchê, life, spirit, consciousness) or soul (anima, incorporeal or spiritual 'breath' which animates the human body)
(see also Philosophy of Mind: A Comprehensive Introduction, W. Jaworski, John Wiley & Sons, 2011 and The Oxford Handbook of Philosophy of Mind, B. McLaughlin, A. Beckermann, S. Walter, Oxford Handbooks Online, 2009). Epistemology determines the nature and the extent of human knowledge. It is the study of knowledge and justified belief. It attempts to answer the basic question: what distinguishes true (adequate) knowledge (Επιστήμη) from false (inadequate) knowledge? Epistemology deals with three fundamental questions. What is the nature of propositional knowledge, knowledge that a particular proposition about the world is true? How can we gain knowledge? What are the limits of our knowledge?
(see also Epistemology, S. Everson, Cambridge University Press, 1990 and A Companion to Epistemology, J. Dancy, E. Sosa, M. Steup, John Wiley & Sons, 2009). Ethics involves systematizing, defending, and recommending concepts of right and wrong behavior
(see also Philosophical Ethics, S. Darwall, Westview Press, 1997). Political philosophy studies what makes a government legitimate, and what rights and freedoms it should protect and why
(see also The Oxford Handbook of the History of Political Philosophy, G. Klosko, Oxford University Press, 2011).

Philosophy can be divided into theoretical philosophy and practical philosophy. Theoretical philosophy can be divided into natural philosophy, theoretical philosophy as such and philosophy of the divine (theology). The object of theology is the invisible causes of visible things. Theoretical philosophy as such consists of arithmetic (arithmetica), music (musica), geometry (geometria) and astronomy (astronomia), which as the quadrivium together with the trivium (grammar, logic, and rhetoric) comprised the 'septem artes liberales' or seven liberal arts (based on thinking skills). The liberal arts included also the 'ars logica', in which operations on premises (posits, axioms, propositions) provided a new product (or a being) in the form of the conclusion. Opposed to theoretical philosphy stands practical philosophy, which nowadays consists of moral philosophy (ethics), economical and political philosophy. Traditional practical philosophy, the 'artes serviles', 'artes vulgares' or 'artes mechanicae', consisted of the practical arts such as medicine and architecture. The "artes quae libero sunt dignae" (arts that are worthy of a free man) were opposed to "artes serviles" (servile arts). The opposition between artes liberales and artes serviles or vulgares (commonplace arts) comes from Greek culture where the division is based on the fact that the liberal arts are mental arts that do not require physical exertion, hence they are free (as opposed to the commonplace arts) from the work of the muscles of the hands
(see also Artes Liberales: Von Der Antiken Bildung Zur Wissenschaft Des Mittelalters, J. Koch, Brill Archive, 1976 and Philosophy and the Liberal Arts, E.G. Ballard, Springer, 1989).

Any given philosophical system or philosophical complex has to construct an interconnected topology of models for the macro- meso- and microcosmic scale, which develops into a scalable manifold, both on the physical as on the metaphysical level. Concepts within the ontology of the system have to be portable, scalable and interoperable without causing internal inconsistensies. Conceptual equivalency is to be provided for at all levels, dealing with emerging and collapsing properties. A Pythagorean scalability as in the Pythagorean theorem should be in place in order to interconnect all aspects and scales of the system without interlevel scalar or vectorial inconsistencies. The vector of understanding of the model should be aligned with what it pretends to represent or in other words, the phenomenal model should be topologically consistent with the phenomenal world it intends to represent. Topological consistency as such refers to some correlation, not necessarily to a causal relation between philosophical model and what is being modelled, as we would suppose within a correspondence theory of truth. With regard to what we suppose to be reality (modelled) any philosophical system (model) is only a partial representation, both incomplete (ineffective) and imprecise (inefficient), without even having any idea about the degree of incompleteness or imprecision. We cannot ignore the interference and limitations of language as a tool and intermediate between the phenomenal model and phenomenal world, e.g. the 'linguistic turn' in philosophy, which deals with meaning and reference and the relationship between philosophy and language: "Die Philosophie ist ein Kampf gegen die Verhexung unseres Verstandes durch die Mittel unserer Sprache" but also "Was ist dein Ziel in der Philosophie? Der Fliege den Ausweg aus dem Fliegenglas zeigen.". An internally consistent ontology, both linguistic (concepts) and logical (relations), as such does not guarantee its epistemological validity or relevance
(see also The Philosophy of Information, Luciano Floridi, Oxford University Press, 2011, p. 357 and The Oxford Handbook of Philosophy of Physics, Robert Batterman, Oxford University Press, 2013, p.588 and The Problems of Philosophy, Bertrand Russell, Oxford University Press, 1912 and The Edinburgh Encyclopedia of Continental Philosophy, Simon Glendinning, Psychology Press, 1999, p. 40 and Philosophische Untersuchungen, Ludwig Wittgenstein, Basil Blackwell, 1953, PU 109 and PU 309 and Cours de linguistique générale, Ferdinand de Saussure, Payot, 1985).

This section gives an overview of the history of philosophy and philosophers over the ages and is mainly oriented towards Western Philosophy with some aspects of Eastern Philosophy and African philosophy. Philosophy has a relation with theology (study of a god or gods and the nature of the divine, study of unseen causes) and physics (nature, philosophia naturalis, study of visible causes). Philosophy is also involved in the discussion of the relation and the interaction between physics, metaphysics and theology. The history of philosophy provides a brief historical overview of philosophical ideas and concepts. The basic goal of studying the history of philosophy is to understand the history of the development of philosophical theories
(see also Routledge History of Philosophy (10 volumes), G.H.R. Parkinson, S. Shanker, Editors, Routledge, 2003 and The Oxford Illustrated History of Western Philosophy, A. Kenny, Oxford University Press, 1997 and A Comparative History of World Philosophy: From the Upanishads to Kant, Ben-Ami Scharfstein, SUNY Press, 1998 and Classic Asian Philosophy:A Guide to the Essential Texts, J. Kupperman, Oxford University Press, 2006 and History of Islamic Philosophy, H. Corbin, Kegan Paul International, Limited, 1993 and A Short History of African Philosophy, Second Edition, B. Hallen, Indiana University Press, 2009 and A History of American Philosophy, H. W. Schneider, Motilal Banarsidass Publ., 1946).

A specific philosophical system starts with bootstrapping its first principles into existence. First principles as such are 'reverse engineered' in order to fit the desired image of reality which is at stake. Once particular first principles are put in place, they are mostly used implicitly as absolute premises, without explicitly mentioning or questioning the process through which they came into existence. Deductive reasoning requires absolute premises for which there are no exceptions. Accepting the first principles of the system becomes a matter of faith within the philosophical system itself. Faith in a philosophical system and its first principles comes with faith in and adherence to its underlying paradigm. As such the foundations of any philosophy are therefore contingent as establishing the validity of its first principles is beyond and above reach. Philosophical systems therefore come without warranty, so 'caveat emptor'.
(see also The Structure of Scientific Revolutions: 50th Anniversary Edition, Thomas S. Kuhn, University of Chicago Press, 2012 and First Principles of Philosophy. For the use of students, John Bruce, W. Strahan, 1785 and The Oxford Handbook of British Philosophy in the Seventeenth Century, Peter R. Anstey, Oxford University Press, 2013, p. 375 and Introduction to Paradigms: Overview, Definitions, Categories, Basics, Optimizing Paradigms and Paradigm Engines, Manfred Stansfield, Trafford Publishing, 2001 and Changing Paradigms, Clarke, Thomas and Clegg, Stewart (eds). HarperCollins, 2000).

Those who reject any given set of first principles, start the process of creating new first principles again and this can go on 'ad infinitum'. The process of creating first principles is always a meta-philosophical process, because the normal philosophical mechanism (logic) for discerning truth from non-truth does not apply. Using the accepted premises within the philosophical system itself, allows for comparing the validity of any proposition against the framework of the system (e.g. by means of logic). When however two or more independent first principles are in place, contradictions can arise within the system. Contradictions may arise between propositions of the philosophical system (metaphysics) and Nature or physics, which it is unable to capture in a meaningful way, and which causes cognitive dissonance
(see also First Principles of Philosophy and Their Application to the Subjects of Taste, Science and History, J. Bruce, W. Srahan and T. Cadell, London, and William Creech, Edinburgh, 1785 and First principles of a new system of philosophy, H. Spencer, D. Appleton and company, 1862).

The first principles in philosophy are those foundational propositions or assumptions that cannot be deduced from any other proposition or assumption. All other propositions are subsequently derived from one or more first principles. Depending on the choice of first principles, another philosophy or even theology develops, just as with Euclidean and Non-Euclidean geometry
(see also Metaphysics a Study in First Principles, Borden Parker Bowne, Kessinger Publishing, 2004 and From Observables to Unobservables in Science and Philosophy, Richard J. Connell, University Press of America, 2000, p. 207). The conclusions we arrive at within a given philosophical system are, in many cases, relative functions of arbitrary assumptions made at the outset of the creation of the foundational propositions of the system, and opposing conclusions can be reached via distinct but equally arbitrary assumptions. We have no objective criteria via which a given set of foundational propositions may be established on a firmer foundation than the other. "In the first place, philosophers are free to lay down their own set of principles, but once this is done, they no longer think as they wish-they think as they can" (Etienne Gilson, 1937). When combining opposing or incompatible first principles between philosophical systems anything goes, as leading to 'ex contradictione sequitur quodlibet' or principle of Pseudo-Scotus in traditional logic
(see also Philosophical Relativity, Peter Unger, Oxford University Press, 2002 and The Principle of Relativity and Philosophical Absolutism, Florian Znaniecki, Philosophical Review, 24 (1915): pp. 150-164 and The Unity of Philosophical Experience, Etienne Gilson, Ignatius Press, 1937, p. 302 and Ex contradictione non sequitur quodlibet, Walter A. Carnielli , João Marcos, Proceedings of the II Annual Conference on Reasoning and Logic, held in Bucharest, RO, July 2000).

As for the choice of first principles in philosophy, there exists an historical anatagonism between realism and nominalism. Realism is the view that there are universals that are related to but exist apart from thoughts and individual objects in our world. Nominalism, on the other hand, asserts that reality only exists in particular objects. Universals, therefore, have no reality apart from objects. Realists therefore claim that all entities divide up into two major groups: particulars and universals, while nominalists argue that there are only particulars. Realism and nominalism have to deal differently with the resemblance question. Resemblance is crucial to both sort out things and to explain regularities in patterns of events
(see also Realism and nominalism revisited, Henry Babcock Veatch, Marquette University Press, 1954 and Realism Versus Realism, Chhanda Gupta, Rowman & Littlefield, 2002, p. 53 and The Relativity of Philosophical Systems and the Method of Systematic Relativism, Felix S. Cohen, The Journal of Philosophy Vol. 36, No. 3 (Feb. 2, 1939), pp. 57-72 and The Principle of Relativity and Philosophical Absolutism, Florian Znaniecki, Philosophical Review, 24 (1915): pp. 150-164).

There exists a fundamental antagonism between rationalism and empiricism. The difference between rationalism and empiricism can be summarized in three ways: intuition versus deduction, innate 'a priori' knowledge versus only 'a posteriori' knowledge, innate concept thesis versus the tabula rasa thesis. Rationalist innateness or innatism is opposed to the tabula rasa concept of empiricism. The tabula rasa thesis is related to the so-called Aristotelian-Thomistic peripatetic axiom: "(Praeterea,) nihil est in intellectu quod non sit prius in sensu", which postulates the ability to abstract universal meanings (universalia) from particular empirical data (phenomena)
(see also Rationalism, Empiricism and Pragmatism: An Introduction, B. Aune, Random House, 1970 and Rationalism, Empiricism and Idealism, A. Kenny, Oxford University Press, 1986 and Recollection and Experience: Plato's Theory of Learning and Its Successors, Dominic Scott, Cambridge University Press, 1995, p. 93 and Quaestiones disputatae de veritate, Thomas Aquinas, De veritate, q. 2 a. 3 arg. 19).

There is also an antagonism concerning the position of the inflection point (Wendepunkt) between the paradigms of reason and un-reason. Reason is sometimes considered to be a middle state, between instinct, the lower, and intuition, the higher state of mind. Un-reason covers the domain of instinct and intuition and as such is located "outside" the two inflection points containing reason. The boundaries of reason are not only being regarded as inflection points, but also lead to the idea of 'Nec plus ultra' beyond the 'Columnae Herculis' of reason. The truth value and the validity of reason and un-reason is therefore a matter of debate. The position of the transition between rational, causal, logical and quantitative reasoning and un-reasonable, intuitive or qualitative reasoning has a huge impact on the validity of philosophical statements in between both domains. Crossing the inflection point between reason and un-reason leads to philosophical inconsistencies and proving the validity of a proposition or first principle is not possible when one has to cross the inflection point. Truth preservation by means of logic only operates within the domain of reason. As an example, science (physics) is considered to be an example of reason, while art and religion are examples of un-reason. Immanuel Kant (1724-1804 CE) limited reason to the 'Ding für mich' and left the 'Ding an sich' to un-reason. After the defeat of the French Revolution, some fashionable reactionary philosophers swore allegiance to unreason. Ludwig Wittgenstein (1889-1951 CE) in his Tractatus Logico-Philosophicus mentioned the limitations of reason: "Es gibt allerdings Unaussprechliches. Dies zeigt sich, es ist das Mystische" (TLP 6.522)
(see also Reason and Intuition, Alfred Cyril Ewing, H. Milford, 1941 and Boardman's Discourses on the Principles and Philosophy of the Universe, William Boardman, F. Fulton & Co, 1862, p. 53 and Reason and Unreason, Michael Rustin, A&C Black, 2001 and Routledge History of Philosophy Volume IX: Philosophy of the English-Speaking World in the Twentieth Century 1: Science, Logic and Mathematics, S. G. Shanker, Routledge, 2003 p. 237).

There also exists an antagonism between idealism and realism. Idealism is a theory that professes that reality exists only in ideas, while realism professes that there is an external objective reality. Realism asserts two fundamental things about the world: first, that objects outside of our mind have existence; second, that objects outside of our minds are independent from our minds, that is, that facts about these objects are true or false regardless of our opinions or beliefs. Idealists reject the idea that objects are independent of our minds
(see also The Oxford Handbook of World Philosophy, Jay L. Garfield, William Edelglass, Oxford University Press, 2011, p. 172).

Another antagonism exists between monism and pluralism. Monism describes any philosophy that denies that there are many separate beings in the universe. Pluralism states that the universe has unity, but not the unity of one thing, but the unity of many things that have the fact of existence in common. The debate between monism and pluralism is closely related to the development of atomism and the antagonism between the acceptance of the existence of vacuum (void) and the horror vacui (plenism)
(see also A Pluralistic Universe, William James, University of Nebraska Press, 1996, p. 114-115 and A Companion to Metaphysics, Jaegwon Kim, Ernest Sosa, Gary S. Rosenkrantz, John Wiley & Sons, 2009, p. 432 and Pierre Gassendi's Philosophy And Science: Atomism for Empiricists, Saul Fisher, BRILL, 2005, p. 130).

The way we deal with time has important philosophical consequences. Concerning the philosophy of space and time, there is an antagonism between presentism or possibilism and eternalism. Eternalism can be regarded as the "philosophy of being", while presentism is the "philosophy of becoming". From a presentist point of view, time is divided into three distinct regions; the "past", the "present" and the "future". In this model of time, the past is generally seen as being immutably fixed, and the future as undefined and nebulous. As time passes, the moment that was once the present becomes part of the past; and part of the future, in turn, becomes the new present. In this way time is said to pass, with a distinct present moment "moving" forward into the future and leaving the past behind. In presentism only the present moment exists and as such presentism treats the time dimension differently as compared to the spatial dimensions. Eternalism is another philosophical approach to the nature of time, which takes the view that all points in time are equally "real", as opposed to the presentist idea that only the present is real. The view on the nature of time in Newtonian mechanics changed with the development of general relativity and quantum mechanics. The eternalist point of view is related to the view on time which is modeled as a dimension in the theory of relativity, giving time a similar status to that of space. Eternalism is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time. The growing block universe is another theory of time besides presentism and eternalism
(see also Space, Time, and Spacetime: Physical and Philosophical Implications of Minkowski's Unification of Space and Time, Vesselin Petkov, Springer Science & Business Media, 2010, p. 208 and The discovery of the conservation of energy, Yehúda Elkana, Harvard University Press, 1974, p. 1-22 and The Ontology of Spacetime, Philosophy and foundations of physics Vol. 1, Denis Dieks ed., Elsevier, 2006, p. xv and Time: Limits and Constraints, International Society for the Study of Time. Conference, BRILL, 2010, p. 110).

The concept of time also differs with regards to the way we see it progressing. Time can be seen as linear and one-directional or to exist within a circular and cyclical frame: Time's Arrow or Boomerang. Circular time represents infinity within finiteness. Time can be regarded as evolutionary or revolutionary or eschatological. Time can be regarded to be a continuum or discrete
(see also Changing Concepts of Time, Harold Adams Innis, Rowman & Littlefield, 2004 and Three Concepts of Time, K. G. Denbigh, Springer Science & Business Media, 2012 and Cosmology, Physics, and Philosophy: Including a New Theory of Aesthetics, Benjamin Gal-Or, Springer Science & Business Media, 2012, p. 447 and The Concept of Time in Early Twentieth-Century Philosophy: A Philosophical Thematic Atlas, Flavia Santoianni, 2015, p. 31).

The world is either eternal or it is created ex nihilo. Greek philosophers largely held that matter was eternal and uncreated because the notion of a beginning point for everything seemed absurd to them. Opposed to this is the belief that God alone is eternal and uncreated, and therefore matter cannot be eternal. A distinction is also being made between eternity and sempiternity. Eternity is eternal existence outside of time, which is being reserved for God. Sempiternity is eternal existence, but within time, which is then the case for the world. In this frame of thought, 'eternity' means 'atemporality' and 'sempiternity' means 'everlastingness'
(see also On God, Creation, and the Necessity of a Finite Past, J.L. Micah Petillo, ProQuest, 2008 and The Arrows of Time: A Debate in Cosmology, Laura Mersini-Houghton, Rüdiger Vaas, Springer, 2012, p. 30 and Eternity and Sempiternity, M. Kneale, Proceedings of the Aristotelian Society New Series, Vol. 69, (1968-1969), pp. 223-238 and God, Eternity and the Nature of Time, Alan Padgett, Wipf and Stock Publishers, 2000, p. 46).

Another antagonism exists between the pair of determinism-indeterminism, which intersects with the pair of finalism-mechanism. The basic argument is that either determinism or indeterminism is true, and either way freedom and/or moral responsibility are impossible. The dilemma of determinism or standard argument against free will is an argument that there exists a dilemma between determinism and its negation, indeterminism. Determinism is traditionally considered rational, causal, nomological (law-like), while indeterminism is considered irrational, acausal chance. Finalism is the doctrine that final causes determine the course of all events (teleology), while mechanism postulates no final cause. Mechanism comes down to determinism of the past, while teleology means determinism of the future. Mechanistic determinism also refers to Pierre-Simon Laplace's (1749-1827 CE) omniscient demon for whom past, present and future are equally real in a Newtonian mechanistic clockwork universe. The uncertainty principle of quantum mechanics has removed the burden of Newtonian determinism from the purely materialistic worldview. The uncertainty principle changes the rules of causation as it introduces randomness into physics. It also has an impact on the discussion about free will and free choice. The discussion about free will within a quantum context was part of the Bohr-Einstein debates
(see also The dilemma of determinism, William James, 1884 and Philosophical Enquiries, Margaret Chatterjee, Motilal Banarsidass Publishers, 1987, p. 195 and Quantum Enigma: Physics Encounters Consciousness, Bruce Rosenblum, Fred Kuttner, Oxford University Press, 2011, p. 134 and The Oxford Handbook of Free Will: Second Edition, Robert Kane, Oxford University Press, 2011, p. 6).

These antagonisms are 'Absolute Presuppositions' or 'First principles' which are incommensurable or antinomies. 'Absolute Presuppositions' or 'First principles', as disscussed in Language, Truth, and Logic (1936) of A. J. Ayer (1910-1989 CE) and the Essay on Metaphysics (1940) of R. G. Collingwood (1889-1943 CE), are propositions whose truth is absolutely necessary for either the truth or the falsity of a given philosophical system, but which are not properly capable of truth or falsity themselves. Therefore they are called 'principia neutra' as they can never be part of any rational or logical discussion themselves. Stated otherwise: 'Contra negantem principia non est disputandum' (Auctoritates Aristotelis et aliorum philosophorum)
(see also Kritik der reinen Vernunft, Immanuel Kant, 1781, AA III, 281-382 and Der Gesuchte Widerstreit: Die Antinomie in Kants Kritik Der Praktischen Vernunft, Volume 139, Bernhard Milz, Walter de Gruyter, 2002).

Within any given philosophical system conflicts can even occur between its 'First Principles' or between its 'First Principles' and reality along the way, which may sometimes be difficult to reconcile without starting from new premises. Much creativity and tweaking of concepts has been done to fix these intrinsic flaws in delicate philosophical structures (or they are just being ignored). Mono- , pluri- and polycausality may all require tweaking of premises to save the delicate edifice of a philosophical or even theological system
(see also Introduction to Type Theory and To Be is to be a Value of a Variable (or to be Some Values of Some Variables), George Boolos, The Journal of Philosophy, Vol. 81, No. 8 (Aug., 1984), pp. 430-449). Tweaking the principles of logic or the premises of the system and situation to retrofit the desired outcome to its philosophical foundations, has been used throughout history to avoid the embarrassing confrontation of reality with deficient premises or logical flaws
(see also casuistry). When conflicts arise, something has to surrender, either the principles and logic of the system or reality (the human principles and logic can be the "tail wagging the dog" of reality or may require "obscurantism"). The concepts hypnagogic (toward sleep) or hypnopompic (from sleep) can also be applied to the situation of entering or leaving a philosophical and theological framework
(see also "The Hypnopompic". The Head Trip: Adventures on the Wheel of Consciousness, Warren, Jeff (2007) and Hypnagogia: the Unique State of Consciousness Between Wakefulness and Sleep, Mavromatis, A. (1987), London: Routledge and Kegan Paul). Reasoning from within a fixed philosophical system may require suspension of disbelief with regard to the propositions and principles of the system itself and cognitive dissonance with regard to reality which does not adhere to the principles of the system
(see also The Relativity of Philosophical Systems and the Method of Systematic Relativism, Felix S. Cohen, The Journal of Philosophy, Vol. 36, No. 3 (Feb. 2, 1939), pp. 57-72 and Relativity and Variety of Philosophical Systems, Nathan Rotenstreich, Philosophy and Phenomenological Research, Vol. 41, No. 1/2 (Sep.-Dec., 1980), pp. 187-203 and The Principle of Relativity and Philosophical Absolutism, Florian Znaniecki, The Philosophical Review , Vol. 24, No. 2 (Mar., 1915), pp. 150-164)

The relativity of philosophical systems has to do with the different viewpoints from which they are being constructed, which differs from relativism, which is laxity with regard to a certain system which one proclaims to uphold: "It is easier to fight for one's principles than to live up to them" (Alfred Adler) or as Alain de Lille wrote: "Sed quia auctoritas cereum habet nasum, id est diversum potest flecti sensum, rationibus roborandum est"
(see also De Fide Catholica: Contra Haereticos, Valdenses, Iudaeous et Paganos, Alain de Lille, Book 4, Ch. 30 and Engineering Ethics: Concepts and Cases, Jr. C. E. Harris, Cengage Learning, 2013 and The Principle of Relativity, Alfred North Whitehead, Cosimo, Inc., 2007 and Introduction to Moral Theology (Catholic Moral Thought, Volume 1), R. Cessario, Catholic University of America Press, 2001, p. 234 and The Abuse of Casuistry: A History of Moral Reasoning, A. R. Jonsen, University of California Press, 1988, p. 247).

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Ontology
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Epiphenomenalism

Egypt had a profound impact on the early development of European culture and philosophy, which is why I included this section in European history. From the time of Pharaohs of the Third Dynasty to Pharaoh Khufu or Cheops (ruled around 2580 BCE) of the Fourth Dynasty (builder of the Great Pyramid of Giza), Egypt flourished and was a leading nation in the Mediterranean. Egyptians studied astronomy in Egypt and the lands south of Punt for thousands of years, which is evidenced by the monuments that remain such as the Great Sphinx of Giza and the pyramids. The oldest work of philosophy known to us is the Instructions of Pta'h-hotep, which apparently goes back to 2880 BCE. Ancient Egyptian philosophical thought was closely related to their religious beliefs. Egyptian society was based on the concept of Ma'at, which means balance and order
(see also the Greek concept of Harmonia). The best definition of Ma'at is an amalgam of words, ranging from "truth" to "harmony" to "stability", and the best correlation to Ma'at we can think of outside Egypt is the Taoist understanding of Tao, "The Way". Ma'at is what is right - what is correct. Ideal conduct for ancient Egyptians was both practical and religious. Texts such as the Book of the Dead stress the virtues of charity, benevolence, prudence, social justice, mercy, and the love of intellectual pursuits. Moral thoughts and desires were as important as moral actions. The ancient Egyptians believed that man was composed of three parts: the body, spirit, and soul. The fate of the soul was determined by its actions during life, whether good or bad, and the amulets, prayers, and gifts offered to gain the favor of the gods.

Kemet or Ta-merry (ancient names for Egypt) was the center of learning and people from all over the Mediterranean came to study in the Egyptian Mystery Schools
(see also Kemet and the African Worldview, M. Karenga, Jacob H. Carruthers, University of Sankore Press, 1986). Early Greek philosophers were students or had some contact with the students of the Egyptian institutions of learning. The Egyptian Mystery system was also a secret order. Membership was gained by initiation and a pledge of secrecy. The teachings were graded and delivered orally by the Neophyte; and under these circumstances of secrecy, the Egyptians developed secret systems of writing and teachings, and forbade their initiates from writing what they had learned. After nearly five thousand years of prohibition against the Greeks, they were permitted to enter Egypt for the purpose of their education. First through the Persian invasion of Egypt and secondly through the invasion of Alexander the Great (356-323 BCE). The Greeks made the best of their chance to learn all they could about Egyptian culture. After the invasion of Alexander the Great, Aristotle's school converted the Library of Alexandria into a research center. The city of Alexandria in Lower Egypt became the centre of scientific activity across the Hellenistic world. Out of this tradition Neo-Pythagoreanism, Jewish-Alexandrian Philosophy (e.g. Philo of Alexandria (ca. 20 BCE-40 CE)) Neo-Platonism, and Early Christianity would develop
(see also The Library of Alexandria, R. M. MacLeod, R. MacLeod, I.B.Tauris, 2004).

Ancient Egyptian metaphysics influenced Greek philosophy mainly during the Presocratic period of Greek philosophy. Both Thales of Miletus (ca. 624-ca. 546 BCE) and Pythagoras (ca. 570-ca. 495 BCE) were influenced by Egypt in their philosophy. Aristotle (384-322 BCE) would stand in the Ionian tradition of Thales, while Plato (424/423-348/347 BCE) would stand in the Italiote tradition of Pythagoras
(see also Life and Thought in the Greek and Roman World, M. J. Cary, T. J. Haarhoff, Greenwood Publishing Group, 1985, p. 193 and From Religion to Philosophy, F. MacDonald Cornford, Cosimo, Inc., 2010, p. vi).

Through Mosaic Judaism, Egyptian philosophy and theology would also influence European civilisation. During the Middle ages, both Mosaic Judaism, Aristotelianism and Platonism would converge in Christianity as it was implemented in Roman Catholicism, Orthodox Christianity and later also in Protestantism. Christian religion would become a synthesis of Mosaic Judaic theology and Greek philosophy, both having their ancient roots in Egypt
(see also Gods of Our Fathers, R. A. Gabriel, Greenwood Publishing Group, 2002 and Moses the Egyptian, Jan Assmann, Harvard University Press, 2009).

Weighing of the heart, from the book of the dead of Hunefer

Ancient Egyptian Metaphysics
The Wisdom of the Egyptians
The Ptah-Hotep and the Ke'gemni

Ancient Greek philosophical tradition broke away from a mythological approach of explaining the world, which had prevailed in Babylonia and Egypt. This initiated an approach based on reason and evidence and thereby started the Western tradition of philosophy. Greek philosophers raised the question of "the one and the many". How can there be any genuine unity in a world that appears to be multiple? To the extent that a satisfactory answer involves a distinction between appearance and reality and the use of dialectical reasoning in the effort to understand what is real. Within Greek philosophy Eudaimonia is the self-sufficient, unqualifiedly complete good to be achieved, while Arete is the idea of being "the best you can be" or "reaching your highest potential"
(see also The Cambridge Companion to Early Greek Philosophy, A. A. Long, Cambridge University Press, 1999 and Readings in Ancient Greek Philosophy, S. M. Cohen, P. Curd, C. D. C. Reeve, Hackett Publishing, 2011).

Ancient Greek Philosophy is usually divided into four time-periods:

• Presocratic Philosophy (6th - 5th century BCE): Milesians and Eleatics, Ionian and Italiote (Eleatic, Megarian, Pythagorean) and Sophism
• Classical Philosophy (4th century BCE): Socrates, Plato, Aristotle
• Hellenistic Philosophy (late 4th century BCE - 1st century CE): Cynicism, Epicureanism, Stoicism and Skepticism
• Imperial Philosophy (1st century CE - 6th century CE): Neoplatonism

Early Greek Philosophy or Pre-Socratic philosophy means Greek philosophy before Socrates (469-399 BCE) (but includes schools contemporary with Socrates which were not influenced by him). Initially Greek philosophers tried to explain the entire cosmos, and the Presocratic philosophers strived to identify its single underlying principle. They initiated the quest to identify the underlying eternal and unchanging principles of nature: physis. The presupposed underlying unity was postulated in eternal and uncreated First Matter "prima materia " or hyle prote and elemental building blocks with regard to matter (ex nihilo nihil fit). As for causation, there had to be a chain of causes working within objects and toegether with the fundamental elements or essences, eternal principles which caused change or motion were postulated (or change was rejected as with Parmenides of Elea). For the materialists the underlying first principle was physical, such as the atoms of Democritus (ca. 460-370 BCE), while for the rationalists it were "immaterial principles" (e.g. the numbers of Pythagoras), which could be immanent or transcendent as they would become with Plato (424/423-348/347 BCE). The rationalists share the view of the inferior or derivative reality of matter with regard to their immaterial first principles. In Classical antiquity, the Presocratic philosophers were called physiologoi (E: physical or natural philosophers). Diogenes Laërtius (ca. 3^rd century CE) in his Lives and Opinions of Eminent Philosophers divides the physiologoi into two groups, Ionian and Italiote, led by Anaximander (ca. 610-546 BCE) and Pythagoras (ca. 570-ca. 495 BCE), respectively
(see also The Oxford Handbook of Presocratic Philosophy, P. Curd, D. W. Graham, Oxford Handbooks Online, 2008 and The Presocratic Philosophers, J. Barnes, Routledge, 2013).

The new features of Ionian thought were the tracing back of many phenomena to a few causes; the reduction of quality to quantity; ... and the employment of mechanical models (see The Physical World of the Greeks, S. Sambursky, Routledge, 1956). The monism of the Ionians would combine the primordial substance with the principle of the first mover, which would later become separated with Aristotle (384-322 BCE).

The Milesian school of Greek philosophy was a school of thought founded in the 6th century BCE in Anatolia (Μικρὰ Ἀσία). Thales of Miletus (ca. 624-ca. 546 BCE), Anaximander (ca. 610-546 BCE) and Anaximenes (d. 528 BCE) were the earliest philosophers in the European tradition. It was Anaximander who wrote a Περι φυσεως (Peri physeos), which is the earliest known Philosophical text in Europe. The world-view of the Milesians departed from the mythological world-view of ancient Greece. First of all they departed form the mythological world-view and looked for an explanation of natural phenomena in nature itself. Secondly they based the order of things in nature on immanent laws (nomos) and not on divine intervention. There was no hierarchy in the laws of nature, so all laws acted on an equal base (kratos). Thirdly, reality has a profound geometrical nature consisting of reciprocal, symmetrical and reversible relations.
(see also Les Origines de la pensée grecque, Jean-Pierre Vernant, Presses Universitaires de France, 1962)

The Ionian tradition, and for most historians the Greek philosophical tradition, started with Thales of Miletus (ca. 624-ca. 546 BCE). Thales was from Miletus in Ionia or Asia Minor (Milet in modern Turkey), and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition. Thales attempted to explain natural phenomena without reference to mythology and was tremendously influential in this respect. With Thales started the tradition of speculative philosophy in Greece, which laid the foundations for the Western approach to reality and dealing with the basic philosophical and theological questions of the cosmos and the life of man. Thales is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales' Theorem. Thales' most famous belief was his cosmological thesis, which held that the world started from water and was not created by the Gods. If one substance can be transformed to another substance, might that be because they are, at root, merely different forms of the same 'materia prima'? Thales and other Greek philosophers postulated a 'prote hyle' or 'materia prima', because they wanted to understand the transformations that they observed daily in the world. Other philosophers of the Milesian school had other ideas about the 'prote hyle' or 'materia prima' that constituted everything
(see also Explaining the Cosmos: The Ionian Tradition of Scientific Philosophy, D. W. Graham, Princeton University Press, 2009).

Anaximander ca. 610-ca. 546 BC) also lived in Miletus, belonged to the Milesian school and learned the teachings of his master Thales. He succeeded Thales and became the second master of that school, where he counted Anaximenes (d. 528 BCE) and arguably, Pythagoras (ca. 570-ca. 495 BCE) amongst his pupils. Anaximander offers an account of the origins of the world that illustrates the new Ionian style of explanation. Anaximander does not invoke interactions among divine beings, but rather restricts himself to interactions among natural processes. He was the first to put forward a theory of the nature of the world, not only the matter of which it is made, but also the process of growth from the limitless into the limited (manifold) by eternal motion (dyne). Anaximander takes the original state of the world to be some everlasting stuff: apeiron ("the boundless" or "the indefinite"). Unlike Chaos, this stuff is not divine. He rejected a determinate first principle (water) as the primordial element, because of the contradiction of using a determinate substance to give rise to other determinate substances. Anaximander claimed that an 'apeiron' principle gives rise to all natural phenomena which evolved out of it. The Greek word peras means limit or boundary, and "a-peiron", means without boundaries, boundless or indeterminate. The apeiron, which in itself is a spaceless and timeless manifold, is the boundless giver of boundaries. Anaximander was the first philosopher to employ, in a philosophical context, the term arkhê, which until then had meant beginning or origin. For him, it became no longer a mere point in time, but a source that could perpetually give birth to whatever will be. For Anaximander, the principle of things, the constituent of all substances, is nothing determined and not an element such as water in Thales' view. He postulated the apeiron as an immortal and indestructable substance that, although not directly perceptible to us, could explain the opposites he saw around him. The 'to apeiron' itself remains forever inaccessible to empirical inquiry, which created the problem of it being inaccessible to human understanding. For Aristotle, 'to apeiron' would be part of the world, and in fact is the fundamental stuff of the world. According to him, the Universe originates in the separation of opposites in the primordial matter or 'apeiron'. When apeiron was in peiron and steered the cosmic "arrangement", it was known as logos and likened to a fire. It embraces the opposites of hot and cold, wet and dry, and directs the movement of things; an entire host of shapes and differences then grow that are found in 'all the worlds' (for he believed there were many). Anaximander maintains that all dying things are returning to the element from which they came (apeiron). The influence of the apeiron initiates a ceaseless dialectical motion of opposites. The sum of intelligible forms in the universe comprise that harmonic order which is the knowable cosmos, in opposition to chaos as the image of unrealised potential. Intelligibility implies measurability; a thing imbued with intelligible form is seen to possess circumference, weight and all the other attributes that make it accessible to man's reason. This cosmology contains three factors: a primary substance (apeiron), an order disposition or structure (peiron), and the process by which this order arises: "αρξηαεν ... ειρικαε τον οντον το απειρον εχ ον δε ηε γενεσις εστι τοις ουσι και ταεν πητηοραν εις ταυτα γινεστηαι κατα το ξηρεον διδοναι γαρ αυτα δικαεν και τισιν αλλαελοις ταες αδικιας κατα ταεν του ξηρονου ταχιν". In forming boundaries out of the 'apeiron' or continuum (syneches), in drawing clear-cut distinctions of any kind, a spatial and temporal context is required. The forming of boundaries accompanies the process of individuation and the cosmos can be described as the set of all defined, or bounded things which exist in time. Anaximander offers a physics according to which the "things that are perish into the things out of which they come to be, according to necessity, for they pay penalty and retribution to each other for their injustice in accordance with the ordering of time" (Die Fragmente der Vorsokratiker, Diels-Kranz, B1 & A9 and The apeiron of Anaximander: a study in the origin and function of metaphysical ideas, P. Seligman, Greenwood Press, 1974 and Anaximander and the Origins of Greek Cosmology, C. H. Kahn, Hackett Publishing, 1994 and In the Beginning Was the Apeiron: Infinity in Greek Philosophy, Adam Drozdek, F. Steiner, 2008, p. 15).

Anaximenes (d. 528 BCE) would continue Anaximander's research program, developing it by introducing a theory of change that involves impersonal mechanisms (rarefaction and condensation) rather than a vague appeal to divine justice. For Anaximenes air is the source of everything (that from which everything else comes) by virtue of being the "underlying nature"; there is a set of basic elements ordered by their relative density and these elements arise from each other by being rarefied or condensed. Anaximenes put forward that air is the source (arche) of the basic elements, that the basic elements come to be (gignesthai) from air. This is being interpreted in two ways: Material Monism (by Aristotle) or Generating Substance Theory (GST). The term "substance" in both cases is technical as it refers to something that is physical (as opposed to supernatural), concrete (as opposed to abstract), and independently existing. By proposing air as the basic source, the world becomes entirely knowable, with nothing beyond our powers of inquiry (avoids the need for obscurantism). By proposing rarefaction and condensation as the mechanism of change, Anaximenes offers something like a (non-mathematical) scientific law. For, according to his theory, when certain conditions are met (e.g, air is sufficiently compressed), a particular result inevitably occurs (e.g., wind arises). The mechanism underlying changes leaves no room for arbitrary or mysterious interventions by deities; nor does it appeal to vague analogies with anthropocentric concepts such as retribution and justice. Change, according to Anaximenes, is neither spontaneous nor capricious; instead, it is predictable and a matter of necessity
(see also Science In The Ancient World: An Encyclopedia, R. M. Lawson, ABC-CLIO, 2004, p. 15-16).

Heraclitus of Ephesus (ca. 535-ca. 475 BCE) believed in ever-present change (Panta rhei) in the universe and the unity of opposites. Change produces in eternal and innumerable instances its opposite: from hot to cold, from solid to vaporous, from light to dark, from life to death. For Heraclitus opposites imply, again, an ulterior self-identity. Hence his insistence that, "The path leading up is the same as the path leading down". The world for Heraclitus does not consist of things; rather all things are stages of processes of transformation. Phenomena comprise the objects and occurrences of change and the agent of change is fire. All these processes are interlocked and continuous. Everything comes from fire an returns to it and Fate governs the changes. Change transforms objects and states along an axis whose poles represents opposites; these opposites are compresent. Through all transformations, structure (logos, self-identity-in-multiplicity) is maintained (preserved). Therefore it is legitimate to say of any object or occurrence, "in changing, it remains the same"
(see also Sources of Metaphysical Thinking in Presocratic Philosophy by Jürgen Lawrenz). Heraclitus also held that a person's 'ethos' is their daimon, or fate. The word for character in ancient Greek was 'ethos', from which we get our word "ethics". ετηος αντηροπος δαιμον ("Ethos Anthropos Daimon", A man's character is his fate, Diels-Kranz Fragment B119, ipsissima verba). He thought that character, the essence of the individual, determines his or her experience; Character, the tone of the individual, resonates with the music of his destiny. It is the flaws of character that are tragic. Viewing destiny in this way, the fates are not outside us, in the heavens, weaving and cutting the threads of our lives. Instead, they are consonant with our character. This consideration is at the root of the world view that good things happen to good people
(see also Heraclitus of Ephesus: The Fragments of the Work of Heraclitus of Ephesus on Nature and Heracliti Ephesii Reliquiae, Kessinger Publishing, 2010 and Heraclitus: translation and analysis, Heraclitus (of Ephesus.), D. Sweet, University Press of America, 1995).

He rejected the Pythagorean ideal of harmony as peaceful coexistence, Heraclitus saw the natural world as an environment of perpetual struggle and strife. All entities come to be in accordance with the λογος (E: Logos). What is needed is not simply more sense experience or more information, but an improved way of comprehending the message (Logos) that the world offers to man. People need to have a proper grasp of the world and their place in it. Thought (gnome) is considered to be the agency that mediates true experience, the idea that judgement, knowledge and understanding issue in wisdom (logos) and on the exaltation of the supreme intellectual principle: that nature is intelligible precisely because the logos 'rules' phenomena. To know something is to have brought that experience inside and to have fashioned the experience according to one's cognitive reach and versatility. Heraclitus accepted the evidence of the senses as in some way valuable as opposed to Parmenides of Elea (early 5^th century BCE). Heraclitus seems to have been one of the first philosophers, if not the very first, to have put into practice an idea that has since gained ground down the centuries of philosophical reflection: that language should be used in a symbolic and constrained fashion, as far distant as possible from everyday use, if it is to be appropriate to the intrinsic nature of things. This particular use of language brought out a new meaning of the word logos, in which it was generalised to refer to a whole set of circumstances that all expressed a Law of the Universe. This Law involved an underlying harmony, a preoccupation that paralleled that of the Pythagoreans, which implied that all parts of the Universe were in proportion to one another. This Law or Reason also implied, and this is one of the fundamental themes in Platonic thought, that there was a certain analogy between the structure of the Universe and the structure of linguistic forms, ranging from poetic language to apparently abstract mathematical formalisation. Heraclitus denies that profound paradoxes exist, citing the necessary conjunction of opposites in a single entity. This was to become the basis of his cosmology and which also implied the eternity of the world (the basis principles give and imply the answer to the question of eternity). This cosmology was also a theology, because it was the underlying basis for the divine, the Law of matter whose substrate was the eternally changing element Fire. Fire should be looked upon as the originating principle and a metaphor for transformation. Herakleitos rejected 'air' on the sound objection that all specific substances are questionable candidates for the role of an ultimate 'primal matter'. Here Heraclitus concurred with the monist theories of Anaximenes and Anaximander. for Herakleitos fire is not to be regarded as an element, predominating equivalently to (say) water in the constitution of the world, but as the agency by which the elements of the world are transformed from one material constitution into another. He said that things came from Fire and of necessity returned to Fire, in processes similar to Rarefaction and Condensation, rising as smoke to the Heavens, and followed by a return to the final Fire. Anaximander had used the concepts of 'thickening' and 'thinning' (pycnosis/manosis). For Heraclitus he law of creation and destruction was still the supreme Harmony. Fire condensed and, perhaps via Air, became Water, which condensed in its turn and produced Earth. This was the descending path. But conversely, Earth became liquefied into Water, and Water rose as vapours, some shining and of the same nature as Fire, others dark and thick and of the same nature as damp. Clouds of Fire came together to form stars, while the black clouds formed a screen between these burning stars and the Earth, hiding the vigour of their fires. For Heraclitus, the upward path has no end, and everything we are will return to the eternal Fire. He introduced the concept of Logos, which he regarded as both immanent and transcendent. For Heraclitus the Logos is discernable only by a select, rationally gifted few, he emphasized its ineffable yet noetic qualities. Logos by Heraclitus is intimately connected to reason, which, he concluded, provides a more viable means for discerning truth than the divine mysteries
(see also The Art and Thought of Heraclitus, Charles H. Kahn, Cambridge University Press, 1981)

Empedocles (ca. 495-435 BCE) left us two works (fragments) On Nature and Purifications. In these works, Empedocles organised the knowledge revealed by the λογος (E: logos) of things, in the Pythagorean fashion, and also developed an idea diametrically opposed to the Heraclitean approach, that of a perfect correspondence between sensory perception and the intrinsic reality of nature. In On Nature Empedocles states that everything is composed of four material elements ("roots"); these elements are moved by two opposing forces. The elements are fire, air, earth, and water; the forces are Love and Strife or Attraction and Repulsion. Empedocles was the first to distinguish clearly these four elements, traditional in Greek physical theory. The concept of the elements goes back to the Babylonian Enûma Eliš (The Seven Tablets of Creation), a creation myth written between the 18^th and 16^th centuries BCE, which describes four cosmic elements: the sea, earth, sky, and wind. For Empedocles these primal elements or forces are eternal and unchanging, but everything else comes to be and passes away because each is composed of elements that successively combine to form them and separate at their destruction. The four elements come together and blend under the agency of Love, and they are driven apart by Strife, in a continual alternation. These classical elements are representatives of the different physical states that matter can adopt. Earth represents not just soil or rock, but all solids. Water is the archetype of all liquids; air, of all gases and vapours. Fire is a unique and striking phenomenon. Fire is actually a dancing plasma of molecules and molecular fragments, excited into a glowing state by heat. It is not a substance as such, but a variable combination of substances in a particular and unusual state caused by a chemical reaction. In experiential terms, fire is a perfect symbol of that other, intangible aspect of reality: light. The elements were types, and not to be too closely identified with particular substances
(see also The Poem of Empedocles: A Text and Translation With an Introduction, Empédocles, University of Toronto Press, 2001 and Empedocles: An Interpretation, S. Trépanier, T. L. Wood, Taylor & Francis, 2013).

Leucippus (first half of 5th century BCE) and Democritus (ca. 460-370 BCE), the Laughing Philosopher (Abderitan laughter), formulated an atomic theory for the universe. The atomistic theory began as an endeavor to overcome some consequences of the Eleatic school of philosophy. Democritus was born in Abdera, and the terms Abderitan laughter, which means scoffing, incessant laughter, and Abderite, which means a scoffer, are derived from Democritus. Atomism was a middle way between the philosophy of Parmenides of Elea (fl. 5th century BCE) (Oneness, denying motion) and Heraclitus (ca. 535-ca. 475 BCE) who stated that things are constantly changing (universal flux). The Atomist philosophy is also a logical development of the philosophy of Empedocles (ca. 495-435 BCE). But the Atomists rejected the doctrine that the four elements were the fundamental particles and the metaphorical powers of Love-Strife. Instead they sought a purely mechanistic philosophy. Leucippus and Democritus did not accept the Eleatic postulate that "everything is one" (monism) and that change and motion are illusions of the senses. Parmenides had said the void is a fiction, because saying the void exists would mean to say there is something that is nothing, which he thought was a contradiction in itself, but Parmenides was deceived by thinking of "being" in the sense of "material being" which is not identical. Leucippus affirmed at the same time the non-reality of space and its existence, meaning by non-reality, non-corporeity. This position is expressed by saying that "what is not" is just as much real as "what is" as opposed to Parmenides. Space/void is not corporeal, but it is as real as body. Thinking of the void as real would have overthrown Parmenides' theory, because allowing the void to exist as "space bereft of body" implies the opposite of classical monism and the "horror vacui", or plenism. Plenism is the philosophical theory that there are no vacuums in nature
(see also The atomists, Leucippus and Democritus, University of Toronto Press, 2010 and Presocratic Reflexivity: The Construction of Philosophical Discourse C. 600-450 Bc, Volume 3, B. Sandywell, Routledge, 1996, P; 377).

Overthrowing monism monism was exactly what Leucippus and Democritus intended. They put forward the concept of atoms, which replaced the monism of Parmenides with the plurality of atomism. The atomists rejected the duality of Parmenides between mind and matter for the unity of mind an matter. Democritus began with stating a notion of space that served as its premise. Rather than an attribute of matter that describes its extension, Democritus characterizes space as a receptacle for stationary and moving objects, which, under certain circumstances, can as well be completely empty (rejecting the second part of Parmenides's first principle). For Democritus atoms are physically, but not geometrically, indivisible; between atoms lies empty space; atoms are indestructible (ousiai); have always been, and always will be (eternal), in motion; and there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. Atoms moved eternally in the void, but at some point of time collisions between atoms occurred, those of irregular shape becoming entangled with one another and forming groups of atoms. In this way the vortex is set up, and a world (kosmoi) is in process of formation. Another effect of the movement in the void is that atoms which are alike in size and shape are brought together as a sieve brings together the grains of millet, wheat, and barley. In this way are formed the four 'elements': earth, air, fire and water. The atoms are eternal and unchanging as opposed to Heraclites who stated that everything changes, but the atoms are not a unified first principle as opposed the Parmenides. The solidness of a material corresponds to the shape of the atoms involved. By postulating that there exist and infinite number of atoms, there also existed (the possbility of) an infite number of universes. As man also consisted of atoms, just like the rest of the universe, man was a microcosm in itself because he contained atoms of every kind and was subjected to the same laws as the (rest of) the universe. Man like anything else is a conglomerate of atoms, which only exists as long as the forces of attraction between the composing atoms are not broken by external forces. The conglomerate therefore does not constitute a higher level unity in itself, but remains the result of atomic interactions. The atomists accepted that motion (change) required a void (nothingness) as opposed to the theory of the Eleatics. Nature for the atomists exists only of two things, namely atoms and the void that surrounds them. The void is infinite and so atoms can move through the infinite universe
(see also Ancient Atomists on the Plurality of Worlds, James Warren, The Classical Quarterly New Series, Vol. 54, No. 2 (Dec., 2004), pp. 354-365 and The Blackwell Guide to Ancient Philosophy, Christopher Shields, John Wiley & Sons, 2008).

Leucippus meant to ascribe the motion of the atoms to chance: to him the eternal motion and the continuation of motion required no explanation. His cosmology needed no external Power (Love-Strife/Nous); the Atomists were content and sought no "First Unmoved Mover". The approach that uses these concepts, the mechanistic approach, is complementary to the vitalist or finalist approach. Physical events were viewed from the mechanistic standpoint as opposed to a finalistic or "teleological" view. According to the mechanistic and materialistic view, matter is a sufficient cause and explanation for all natural phenomena. The atomistic theory reduces the status of the Gods as atoms are eternal and makes the soul into the dust of particles (special types of small atoms). Individual atoms become governed by necessity and chance. Democritus seems to have believed that Gods are certain "idols" (images) of very great size, which did appear to men. These were "difficult to be destroyed, but not indestructible". They were certainly mere products of the atoms and the void, parts of nature, rather than controllers or inspirers of it. Gods were thought of as "idols" which came into existence because of the fear of man for natural phenomena. For Democritus this fear for natural phenomena was something which was not necessary. His atomistic philosophy aimed at taking away the fear of man for natural phenomena and to diminish the dependency on gods for explaining reality. Democritus thought of the interaction of atoms as eternal and necessary, which seems to leave no room for 'free will'. The atomists developed a fully mechanistic view of nature in which every material phenomenon is seen a product of the atom collisions. Democritus' theory had no place for the notion of purpose (teleology) and the intervention of Gods in the workings of the world. He even held that mind and soul (Democritus makes no distinction between the two) is formed by the movement of atoms. In this regard, his approach to reality was genuinely materialistic
(see also The Anthropic Principle: Proceedings of the Second Venice Conference on Cosmology and Philosophy, F. Bertola, Umberto Curi, Cambridge University Press, 1993, p. 20 and The Atomists, Leucippus and Democritus, University of Toronto Press, 2010, p. 189).

Democritus's views on knowledge and perception were developed largely in response to the Sophists. Although the object of are senses are objective (made of atoms) and our perception of them is mechanistic, it is also purely subjective (mechanistic interaction between the observer and the observed). "By the senses we in truth know nothing sure, but only something that changes according to the disposition of the body and of the things that enter into it or resist it". For the atomists knowledge and perception are closely related and both are immanent. There is no distinction between them as with the Ideas of Plato or the Forms of Aristotle which both postulated a transcendent realm where knowledge existed as a separate noematic reality from the noetic world of the senses. In their mereology or theory of parthood relations the atomists rejected the existence of supra-material entities (universals) with properties in themselves which did not exists at the level of the atoms. Democritus accepted the 'effluence' theory of Empedocles (the whole body is full of pores. In the organs of sense these pores are specially adapted to receive the effluences ("idols") which are continually rising from bodies around us; and in this way perception is explained), but thought of these particles as atoms or images given off by objects. Before they enter the sense organs they are distorted by the air. Democritus tried to account for perception in terms of the motion of these images or differences in their surface texture. Secondary qualities such as colour and smell (as against the actual physical properties of the atoms themselves) are therefore all subjective or conventional (nomos), and so we cannot know objects as they really are. Even mind cannot give us the truth, as what might be supposed to be mental, including the soul, itself consists of atoms and can come into contact only with the atoms given off by objects. Man during his life breaths vital air (pneuma) which provides him with soul-atoms. On the body's death the soul-atoms disperse. There is no immortal soul in man, which exists after death. Atomists only believed in the noetic (physical) plane of reality and denied an independent noematic (metaphysical) plane. For Democritus taking into account anything else than the physical (noetic) plane was of less value than physical reality itself. The metaphyscial level was a mere "idol" or image of reality and taking into account this "less than real" level distorted the perception and conclusions of man in a given situation. Man's understanding of the worls should make sense in itself and be applicable to physcial reality as such. As the gods were also mere "idols", their significance in the evaluation of a situation or condition was also secondary to the perceived reality itself. For Democritus the "communis opinio" has the same value as other "idols" and is secondary to perceived physical reality. By taking physical reality as its starting point and not a single first principle, atomism is extremely adaptive to new observations and situations as opposed to the philosophy of Parmenides. Atomism does not derive its truth value from its first principle like Parmenides, but from the noetic plane. Human thought therefore is subordinate to perception and the goal is to align the mind and soul with everchanging reality. As many (most) people take the wrong path in life, guided by "idols" instead of physical reality, the wrong path is broader than the path of life which is the right path to be taken
(see also A History of Philosophy, Wilhelm Windelband, Wipf and Stock Publishers, 2003, p. 105).

Democritus's ethics was directed against the Sophists. The end of conduct is happiness (eudaimonia), by which he meant not sensual pleasure but well-being. This is to be acquired by attending to balance or harmony, a weighing up of the various pleasures. In this way, he said, we can achieve physical health and a certain calmness or cheerfulness (euthymia) in the soul. There is a struggle to discern and attain that which is good for the soul. We should be guided by the principle of symmetry or harmony. Human freedom (as exemplified by choice) is central to Democritus's ethics: "He who chooses the goods of the soul, chooses the more divine; he who chooses the goods of the tabernacle, chooses the human". It is unlikely that Democritus recognized the inherent contradiction between the ontological determinism of his atomist-mechanical cosmology and the freedom of his ethical system. After Leucippus and Democritus, philosophy made a major turn towards ethics and politics. The atomists were the last in the line of the tradition of the Presocratic natural philosophers whose primary subject was the composition and order of the physical universe. Epicurus (341-270 BCE) would incoporate atomism in his Epicurean philosophical system
(see also Atomism and its critics: from Democritus to Newton, A. Pyle, Thoemmes Press, 1997).

What distinguished the atomists from their opponents was not the belief in tiny particles that make up matter, but the question of what separated them. Democritus supposed that atoms move about in a void. Other philosophers ridiculed and rejected this idea of "nothingness" or "non-being", maintaining that the elements must fill all of space. Anaxagoras (ca. 500-428 BCE) claimed that there was no limit to the smallness of particles, so that matter was infinitely divisible. This meant that tiny grains would fill up all the nooks between larger grains, like sand between stones. Aristotle asserted that air would fill any void between atoms
(see also Readings In Ancient Greek Philosophy (Third Edition): From Thales To Aristotle, S. M. Cohen, P. Curd, C. D. C. Reeve, Hackett Publishing Company Incorporated, 2005, p. 64 and The Legacy of Parmenides: Eleatic Monism and Later Presocratic Thought, P. Curd, Princeton University Press, 1998, p. 206).

The number of primary elements differed, but the naturalistic principle remained. Naturalism for Greek philosophers was mostly essentialist and concept-realist. Objects had a substantial ground, base or foundation. Concepts conveyed absolute reality (realism). Substance denoted whatever remained identical with itself, i.e. a thing depending upon nothing else for its existence than itself. Conceptual thought had direct access to this ultimate reality, either by remembering ("anamnesis" - Plato) or by abstracting ("intellectus agens" - Aristotle). Designating one (ontological monism), two (metaphysical dualism) or more (metaphysical pluralism) foundational substances did not alter the view of Nature as consisting of entities inherently possessing their properties from their own side. Being quasi-determinist and self-enclosed, all events are probabilistically determined solely by other events in Nature, not by an absolute "hypokeimenon" ontologically transcending it. When this essentialism, to explain Nature as a whole, posited a supreme "substance of substances", it either viewed it as transcending the world (cf. a supreme idea of ideas or an Unmoved Mover) or identical with it (cf. the Stoic "pneuma"). Today scientists also put forward that "matter" is acted upon by a limited set of "forces" (causation, the theory of relativity however blurs the boundaries between matter and energy or substance and proces). With the dawn on relativity the objects of Nature are no longer characterized as substances (or self-powered entities, properties or states), but as processes which go the way of occasions. If a supreme "logos" is considered, then merely as an immanent architect creating "ordo ab chao" out of eternal elements (the classical Greek or Indo-European concept), but not as a transcendent creator who created the world "ex nihilo" (the classical Semitic concept)
(see also Space-Perception and the Philosophy of Science, P. A. Heelan, University of California Press, 1988, p. 256).

The Italiote philosophers comprise the Eleatic and the Pythagorean schools of philosophy. Because of the Persian domination, philosophy moved from Ionia to the coasts of Magna Graecia, southern Italy and Sicily. The Megarian school founded by Euclid of Megara (ca. 430-360 BCE), one of the pupils of Socrates (469-399 BCE), created a synthesis of both Eleatic and Socratic philosophy
(see also Rome and the Western Greeks, 350 BC - AD 200:Conquest and Acculturation in Southern Italy, K. Lomas, Routledge, 2013, p.95).

Parmenides of Elea (early 5^th century BCE) was the founder of the Eleatic school of philosophy in the Greek colony Elea in Southern-Italy. Xenophanes of Colophon (ca.570-ca.475 BCE), Parmenides, Melissus of Samos (5^th century BCE) and Zeno of Elea (ca. 490-ca. 430 BCE) are to be reckoned as belonging to this school. Xenophanes may also be regarded as the founder of te Eleatic school as Parmenides is supposed to have been his pupil, and Melissus, and especially Zeno, are called the pupils of Parmenides. Xenophanes criticized the belief in a pantheon of anthropomorphic gods which was then current, and Parmenides developed his ideas further, concluding that the reality of the world is "One Being", an unchanging, timeless, indestructible whole, in opposition to the theories of the early physicalist philosophers
(see also The Eleatic School, C. M. Bakewell, Kessinger Publishing, 2010 and The Legacy of Parmenides, P. Curd, Princeton University Press, 1998).

The Eleatics put forward a radical monism or doctrine of "One Being", according to which all that exists (or is really true) is a static plenum of Being as such, and nothing exists that stands either in contrast or in contradiction to Being. They rejected the idea of movement (change), because movement would require a void, which is nothing, but a nothing cannot exist (Parmenides Diels-Kranz Fragment B7, ipsissima verba). They rejected any input from sensory experience. Instead, the Eleatics felt mathematics to be the method of arriving at the truth. The Eleatics defended the unity and stability of the universe. Parmenides and Melissus generally built their arguments up from indubitably sound premises (first principles), while Zeno primarily attempted to destroy the arguments of others by showing their premises led to contradictions ("reductio ad absurdum"). Parmenides was a rationalist and rejected the world of the senses and he rejected that anything could change (substance). For the pre-Socratic philosophers, the proper objects of sense-experience are qualities such as hot and cold, dry and wet, light and dark. These qualities tend to come in opposing pairs, so that what is hot is not cold, and what is cold is not hot. In forming opinions which describe sense-experience, we freely use language to name the opposing qualities. But Parmenides regarded this as an abuse of language and refers to the habit of naming two thought-forms; wherein men have erred, because one of the forms ought not to have been named (not-being). He pointed to the problem with naming one of the thought-forms of pairs, and the problem lies in the fact that in some sense it is intended to refer to what (it) is not. Parmenides can claim that what is not cannot be thought (episteme), though it may be an ingredient in opinion (doxa). For Parmenides what is thought cannot 'not be'. Something therefore is true if and only if it is about what is, and something is false if and only if it is about what is not. From the fact that all thought (episteme) is about what is, it follows that all thought is true. From the fact that all opinion (doxa) is intended to be about what is not, it follows that all opinion is false. The consequence of this position is the rejection of sense experience and therefore empiricism. One therefore cannot close the hypothesis-experiment (perception) circle in this system in orde to achieve (more) certainty. Parmenides with his system had created a distinction between appearance and reality, which would become the basis for the Aristotelian definition of truth.

Parmenides wrote a poem entitled On Nature, in which he expressed his philosophical views; only fragments of this work have survived, quoted in the works of others. First, On Nature opened with a proem (prooimion), which served as an introduction to the entire work. Second, there was a section called "the way of truth" (alêtheia) in which Parmenides explains the nature of reality. Third, following "the way of truth" is a section known as "the way of opinion" (doxa) in which Parmenides describes how reality deceptively appears to human beings. Parmenides wanted to create a sound foundation or first principle for his cosmology and attempted to build his metaphysics on basis of the logical conclusions derived from a postulated axiom or first principle. Paremnides used λογος for the first time in the sense of a dialectical argument (Parmenides Diels-Kranz Fragment B7, ipsissima verba). The most basic, necessary or self-evident truth from which Parmenides deduces other, corollary truths is that "It is" (estin). According to Parmenides, as contrary to the world of common sense as this may be, insofar as what is, is, it is impossible for it not to be. What is, therefore, is necessary: it cannot not be. If A is A, A cannot be B, where the second part enforces the certainty of the first. His point is that one cannot conceive of what is not, from which it follows nothing cannot be: it is impossible to hold that something is not or that nothing is. Only what can be conceived can be and can be true. Something is true if and only if it is about what is, and something is false if and only if it is about what is not. A central Parmenidean thesis is that all thought is about what is, and no thought is about what is not as you cannot know not-being and cannot express it. From the fact that all thought is about what is, it follows that all thought is true. From the fact that all opinion (doxa) is intended to be about what is not, it follows that all opinion is false. What is false is what is not, and what is not cannot be the object of thought.

For Parmenides there can be no creation, for being cannot come from not-being; a thing cannot arise from that which is different from it. He also argued that movement was impossible because it requires moving into "the void", and Parmenides identified "the void" with nothing, and therefore (by definition) it does not exist. That which does exist is The Parmenidean One, which is timeless, uniform, and unchanging (monism). Reason for Parmenides was the only reliable source for finding truth. Parmenides conceived the duality of appearance and reality. We must distinguish sharply between the many mere appearances that are part of our experience (senses) and the one true reality that is discernible only by intellect (logos, reason). Zeno is considered to be the father of dialectics (the exchange of propositions and counter-propositions to arrive at a conclusion) and the first to use the reductio ad absurdum, attempting to destroy the arguments of others by showing their premises led to contradictions as in Zeno's paradoxes of which the most famous are: Achilles and the tortoise, the Dichotomy argument, and an arrow in flight. These paradoxes of plurality, attempted to show that ontological pluralism, a belief in the existence of many things rather than only one, leads to absurd conclusions. The fundamental problem of the paradoxes is that they mix a metaphysical plane which is incompatible with the concept of change or plurality in nature, with change at the natural or physical level. The rejection of natural change at the physical level in order to obtain absolute truth (certainty) at the metaphysical level, was the Achillesheel of Parmenides's metaphysics.

The Megarian school (Eristics, Dialecticians) was founded by Euclid of Megara (ca. 435-ca. 365 BCE), one of the pupils of Socrates (469-399 BCE), who created a synthesis of both Eleatic and Socratic philosophy
(see also History of Philosophy (3 Vols. Set), W. Turner, Global Vision Publishing Ho, 2007, p. 73-74 and Greek Philosophers As Theologians, A. Drozdek, Ashgate Publishing, Ltd., 2007, p.145).

With Parmenides of Elea (early 5^th century BCE), the Megarics believed in the 'One Absolute Being' which they combined with the essential concept of Socrates, which was 'Form of the Good'. The Good is identified with Being. Being, the One, Intelligence, providence, the Good, divinity, are merely different names for the same thing. Becoming, the many, evil, are the names of its opposite, not-being. Multiplicity is thus identified with evil, and both are declared illusory. Evil has no real existence and only the Good truly is. The various virtues, as benevolence, temperance, prudence, are merely different names for the one virtue, knowledge of Being. Both Eubulides of Miletus (fl. 4^th century BCE) and Clinomachus of Thurii (4^th century BCE) were disciples of Euclid of Megara. Clinomachus was the first who composed treatises on the fundamental principles of dialectics and founded the Dialectical school. Diodorus Cronus (died ca. 284 BCE) a philosopher of the Dialectical school, was most notable for his logic innovations, including his master argument fomulated in response to Aristotle's discussion of future contingents. Aristotle thought statements about the future lack any truth value. They are neither true nor false until the future time when they become true or false (not determined). The Master Argument is a logical contradiction between three propositions:

• every past truth must be necessary (past, actual)
• an impossibility does not follow from a possibility (no temporal relation)
• something is possible which neither is nor will be true (future, potential)

Pythagoreanism is the philosophy of a group of philosophers active in the fifth and the first half of the fourth century BCE. Pythagoras (ca. 572-ca. 500 BCE) set up an organization which was in some ways a school, in some ways a brotherhood. For the members what was done and taught among the members was kept a profound secret towards all. Candidates had to pass through a period of probation, in which their powers of maintaining silence or verbal restraint (echemythia) were especially tested, as well as their general temper, disposition, and mental capacity. For the Pythagoreans 'echemythia' was a discipline to be observed by the initiated in order not to disclose the truths they were learning about the divine. The verbal restraint also referred to Harpocrates, the Greek god of Silence and Secrecy. The Pythagoreans were divided into an inner circle called the 'mathematikoi' ("learners") and an outer circle called the 'akousmatikoi' ("listeners"). These two groups developed into two separate schools of thought. The 'akousmatikoi' focused on the more religious and ritualistic aspects of Pythagoras' teachings, while the 'mathematikoi' extended and developed the more mathematical and scientific work he began
(see also The Cambridge Companion to Early Greek Philosophy, A. A. Long, Cambridge University Press, 1999, p. 78). The 'akousmatikoi' claimed that the 'mathematikoi' were not genuinely Pythagorean, but followers of the "renegade" Pythagorean Hippasus of Metapontum (fl. ca. 500 BCE). The 'mathematikoi', on the other hand, allowed that the 'akousmatikoi' were indeed Pythagorean, but felt that they were more representative of Pythagoras' real views. The 'mathematikoi' eventually became closely associated with Plato and Platonism, and much of Pythagoreanism seems to overlap Platonism. The 'akousmatikoi' became wandering ascetics, finally joining the Cynicism movement of the 4^th Century BCE
(see also Pythagoras and Early Pythagoreanism, C. J. T. de Vogel, Van Gorcum & Company, 1966 and Lore and science in ancient Pythagoreanism, W. Burkert, Harvard University Press, 1972 and Plato and Pythagoreanism, P. S. Horky, Oxford University Press, 2013, p. x).

Pythagoreanism is characterized by its mathematisation of the first principles and its identification of the supreme archè with the One or the Monad. The Pythagoreans developed both a "theoria" and a "cosmology" about the universe. Theoria is a Greek word meaning contemplation and observation and theoria was the contemplative and mystical part of the tradition held by the 'akousmatikoi'. The basis of this Pythagorean tradition was the Orphic mythology, especially the Orphic cosmogenesis. Theoria contained the mystical understanding of the universe, and cosmos was the rational or scientific study and perception of the world. Theoria and kosmos were closely linked to each other, like two sides of a single coin. Theoria was the mystery tradition itself, and cosmos the scientific study sprung from it. The cosmology of the 'mathematikoi' was the beginning of scientific thinking about the world. The division between 'akousmatikoi' and 'mathematikoi' resembles the modern division between faith (theology) and reason (science). The two sides remain, but the joining coin in between faith and reason seems to have disappeared
(see also Orphism, Pythagoreanism and the Mysteries, C. H. Moore, Kessinger Publishing, 2010 and From Myth to Reason?: Studies in the Development of Greek Thought, R. G. A. Buxton, Oxford University Press, 2001, p. 79).

Most notable Pythagoreans were Pythagoras himself, Philolaus (ca. 470-ca. 385 BCE), Eurytus (lived ca. 400 BCE) and Archytas (428-347 BCE). The last manifestation of Pythagoreanism was Neopythagoreanism. It began already in the second half of the fourth century BCE among Plato's first successors in the Academy, but particularly flourished from the first century BCE until the end of antiquity. Apollonius of Tyana (ca. 15-ca. 100 CE) and Moderatus Of Gades (1^st century CE) were notable Neopythagoreans. Neopythagoreanism also became influential among the Greeks of Alexandria from the 3^rd century onwards as the Alexandrian School of philosophy. Neopythagoreanism also has close connections to Middle and Neoplatonism and from the time of Iamblichus (ca. 245-ca. 325 CE) is largely absorbed into Neoplatonism. It was the Neopythagorean version of Pythagoreanism that dominated in the Middle Ages and Renaissance. Pythagoras is credited to have initially explored the mathematical relationship within figurate numbers. Figurate numbers are numbers that can be represented by a regular geometrical arrangement or sequence of evenly spaced points. Figurate numbers are most commonly expressed in the form of regular triangles, squares, pentagons, hexagons, etc. For this reason, figurate numbers are also known as the polygon numbers
(see also A History of Ancient Philosophy: The Schools of the Imperial Age, G. Reale, SUNY Press, 1990, p. 237-274).

While Pythagoras of Samos (ca. 570-490 BCE) left no writings, the central focus of Pythagorean teachings remains unclear. Pythagoras founded a brotherhood of disciples in Croton in southern Italy dedicated to philosophia, a term derived from the Greek word philo, meaning "love", and sophia, meaning "wisdom". The term philosophia, "love of wisdom", is first used in Pythagorean circles and Pythagoras said philosophers were "lovers of wisdom". The Hieros Logos (E: Sacred Discourse) of Pythagoras was lost, but fragments may have remained in the Golden Verses
(see also Pythagoras: His Life, Teaching, and Influence C. Riedweg, Cornell University Press, 2008 and Pythagoras: His Life and Teaching, a Compendium of Classical Sources, T. Stanley, Nicolas-Hays, Inc., 2010 and Pythagoras, K. Ferguson, Icon Books, 2011).

Pythagoras became famous for his ideas about number, the fate of the soul (Metempsychosis), as a wonder-worker and for the Pythagorean way of life. For Pythagoras and the Pythagoreans Number is a universal archetype of Nature (physis), "the principle, source, and root of all things." More specifically, everything is composed of "the elements of number," which the Pythagoreans identified as the Limited and the Unlimited. Pythagoras developed, from the apeiron (boundless) concept of Anaximander (ca. 610-546 BCE), the concept that it is only through the notion of the "limit" that the "boundless" takes form. Pythagoras believed that the apeiron had inhaled the void from outside, filling the cosmos with vacuous bubbles that split the universe into many inter-connected parts separated by "void", and that this play of apeiron and peiron takes place according to a natural harmony. The cosmos and everything in it is made up of these two basic types of things: limiters (peras) and unlimiteds (apeiron). Unlimiteds are continua undefined by any structure or quantity; they include the traditional Presocratic prote hule or materia prima. Limiters set limits in such unlimiteds and include shapes and other structural principles. Limiters and unlimiteds are not combined in a haphazard way but are subject to a "fitting together" or "harmonia", which can be described mathematically. As the whole world is structured according to number, we only gain knowledge of the world insofar as we grasp these numbers (cfr. modern bèta-sciences). The Pythagoreans engaged in the study of number theory or arithmetic (number in itself), geometry (number in space), harmonics or tuning theory (number in time), and astronomy (number in space and time). The Pythagoreans divided their teaching into a four-fold system called the Quadrivium, consisting of Arithmetic/Number, Harmonics/Music, Geometry, Cosmology/Astronomy. The study of arithmetic was given before anything else, so fundamental was the doctrine of Number for their philosophical school. Since number and its qualities such as polarity, harmony, and proportion are archetypal principles that underlie physical manifestation, mathematics is discovered rather than invented, and possesses the power to reflect the essential nature of reality, rather than just modeling it or describing it. Moreover, in the Pythagorean view, because number is universal, it is also divine. In a theory known as the Harmony of the Spheres (Musica universalis), Pythagoras proposed that the Sun, Moon and planets all emit their own unique hum (orbital resonance) based on their orbital revolution, and that the quality of life on Earth reflects the tenor of celestial sounds which are physically imperceptible to the human ear. The central focus of Pythagorean thought is in many respects placed on the principle of Harmonia or Divine Harmony. The Universe is One, but the phenomenal realm is a differentiated image of this unity, the world is a unity in multiplicity. What maintains the unity of the whole, even though it consists of many parts, is the hierarchical principle of harmony, the Logos of relation, which enables every part to have its place in the fabric of the all.

Pythagoras was the first person to call the universe a kosmos. The Greek term, which is the root of the word cosmetic, refers to an equal presence of order and beauty. The universe is a cosmos because the phenomena of nature embody geometrical form and proportion. These proportions allow things to unfold and function in the most elegant and efficient ways (which is a fact of nature), but also give rise to beauty (which is a value). In this way, the worlds of "fact" and "value" are not separate domains, but inherently related. In a larger sense, all things are related through whole-part and proportional relationships (analogia). In Pythagorean thought, number gives rise to proportion, and proportion gives rise to harmony. The Greek word harmonia means "fitting together" or "joining together." Harmony and justice is the result of good proportion made manifest, and the kosmos itself is a harmony in which all of the parts are proportionally bound together. While every organism-including the cosmos-is a unity, it is harmony that allows the parts to function together as an integrated whole. Harmony, justice, and proportion relate to Greek medical theory, because healthy organisms possess a type of dynamic balance in which the various elements work together; when lack of harmony prevails, illness will result. Understanding the cosmos is essential for self-understanding, because humanity is a microcosm, a reflection of the entire world-order in miniature. To know the powers present in the greater cosmos-including the divine powers of order, beauty, and reason-allows humans to become aware of the divine, universal principles reflected within our own being.

Pythagoras used both the concept of duality in his philosophy as well as the symbolic meaning of number. The principles of reality as consisting of ten pairs of opposites or the concept of duality was put forward in the Ten Principles of Pythagoras or the Table of Opposites in which Pythagoreans put: finite against infinite, odd against even, one against many, right against left, rest against motion, straight against crooked, light against darkness, good against evil, square against oblong and male against female. The Table of Opposites made the association between the Unlimited, the Even, and Evil. It implied an association between infinity and imperfection, disproportion, or hybris In contrast, the finite and usually every cosmos, especially our own, was conceived as closed and limited, together with regularity, symmetry (for instance, the symmetry of polygons or regular polyhedra) were regarded as symbols of perfection. In appropriate combinations, this set of ten pairs of opposites should be enough to provide an accurate representation of the whole world. The concept of duality would return at the second level of the Tetractys
(see also A History of Greek Philosophy: Volume 1, The Earlier Presocratics and the Pythagoreans, W. K. C. Guthrie, Cambridge University Press, 1979, p.245).

- Triangular (whole numbers), square (odd numbers) and oblong (even numbers) -

Pythagoras taught that number is the basis of reality. Numbers are the first principles of things. He put forward the first physical theory based on observation and formulated and expressed in mathematical language, and confirmed by observation. By measuring the length of a string on a monochord, Pythagoras found that the chief musical or consonant intervals of the diatonic scale (those of octave, fifth, and fourth) are expressible in simple numerical ratios between the first four integers. Since the musical scale depends upon the imposition of definite or limited proportions on the indefinite (unlimited) continuum of sound, the principles of Limit and Unlimited are the first principles of the physical universe. From this is followed that everything can be expressed in numbers. Harmony symbolizes perfection and since harmony is reducible to number, perfection is likewise reducible to number. The universe is harmonious, so it follows that the universe as a whole can be explained in terms of number. Even and the odd are the basic elements of number, and the even is identified with the unlimited (infinite), and the odd is identified with the limited. These basic principles of Pythagorean metaphysics can be visualized by ordering numbers into geometrical figures, such as triangle, square and rectangle. Number theory is thereby linked with geometry. Even numbers are the principles of oblong figures, odd numbers are the principles of square figures, and whole numbers are the principles of triangular figures.

The fundamental role of geometrical construction was part of the more general emphasis laid by Pythagoras and his disciples on the role of memory, or rather the act of accessing memory , or recall (αναμνεσις), in the processes leading to perfect knowledge. It was not enough to know that everyone had a soul which had had numerous experiences during its former lives; it was necessary to be able to revive the memory of the past at any time. Pythagoras assumed the soul to be tetragonal or square, from which comes the importance of the tetrad or tetraktys and of the gnomon. He maintained that the soul of man consists of a tetrad, the four powers of the soul being mind, science, opinion, and sense. Mathematics was seen as a study that purified the soul from its habitual way of looking at the world and its belief that the physical was ultimate reality. Unlike the practical forms of mathematics we are familiar with today, Pythagoras developed ideal systems of mathematics that functioned as intellectual mandalas that guided the soul to a vision of the structure of heaven. Mathematical studies were ladders and bridges to the divine because they share a perfection and beauty that is true of the divine but lacking in the physical world. In the Pythagorean scheme of the cosmos, the soul is an intermediary between the mortal and the immortal, and so is mathematics. Although mathematics concerns plurality and objects imagined to be extended in space (characteristics of the physical world), it also is incorporeal, unchanging, and has a truth that is like the divine. Therefore, the meditation upon and comprehension of mathematical Ideas allows the soul to enter into the Ideas as a genuine intellectual mandala, awakening the energy of the soul and preparing it for the vision of true reality
(see also The Cosmic Paradigm of the Ancient Pythagoreans, Robert Apatow and Pythagoras and the Early Pythagoreans, Leonid Zhmud, Kevin Windle, Rosh Ireland, OUP Oxford, 2012, p. 282).

- The Pythagorean Tetractys with its symbolic elements -

The triangular numbers 1,3, 6, 10, 15, ..., can be generated by adding each successive number to the result of the addition of the former number: 1+2=3, 3+3=6, 6+4=10, 10+5=15, ... . These are called triangular numbers as they can be represented as an equilateral triangle. The symbolic and divine meaning of triangular numbers in Pythagoreanism was reflected in the Tetractys or "Mystic Tetrad", which consisted of ten points arranged in four rows: one, two, three, and four points in each row, which is the geometrical representation of the fourth triangular number. The points of the Tetractys were, by the number in each rank, intended to denote respectively the Monad, the One, or active principle of nature; the dyad, the form of difference; the triad, or world emanating from their union, also the first actual number with beginning, end, and mean; and the quaterniad, the plane of the four elements; the whole number of points amounting to ten (decad), the symbol of perfection or perfect limit, and cosmic paradigm, combining unity (one) and infinity (zero). The decad further extends to the idea of a new beginning of limitlessness. Symbolizing both world and heaven, the decad helps us to understand the creation of the universe. The monad times the dyad times the pentad (one times two time five) results in the decad. Since any number times ten is similar to any number times one, it is similar to the monad; however, the number is brought to a higher level. The decad can be symbolized by the Tetractys, which comprised both the Limited (the Monad, odd) and the Unlimited (the Decad, even). The Tetractys contained in itself the intrinsic nature of the point (unity), the straight line (two), the surface (three, since a triangle is the simplest surface) and space (four, represented by the tetrahedron, the first regular polyhedron and the first three-dimensional figure). For the Pythagoreans it was not so much the numbers themselves as the geometrical properties that went with them that were the basis for understanding the world
(see also Pythagoras: His Life, Teaching, and Influence, C. Riedweg, Cornell University Press, 2008, p.82).

The Pythagoreans identified the particular triangular number ten as profoundly significant for a number of reasons. For one, it embraces the first ten number principles in its geometrical form (ten is not an element in any of the other geometrical number series, i.e., the square, oblong, pentagonal, hexagonal, and heptagonal). This is deeply significant because it expresses what the Pythagoreans recognized as the unifying power of the triadic principle. The triad is the key to all ancient metaphysics because it is the structure or form which naturally unites duality into harmonious union. (Indeed, the Pythagoreans considered the triad, in certain respects, the first true number. In Greek the word for number is arithmos, which comes from the root "ar" which means "to join," as in "h-ar-monia," the very function of the triad.) The monad and dyad were said to be prior to number, being the principles of oddness and evenness respectively, and in this respect the very source of number itself. The Tetractys, like the ancient Egyptian pyramids, is a model of the All, and the triadic form is its divine mystery. Whereas the four parts of the Tetractys are able to embrace the ten archetypal number principles, it is the triadic power of the triangular form that unifies all number and reveals its essence in unity. And herein lies a secret of the Tetraktys. Although reality unfolds in a divine progression of four levels, unity is revealed when we transcend the fourth level of the physical plane and perfect the mind through the study of the divine triads, ascending to a vision of the brilliant light of Being and gaining an understanding of true number, the principle, source, and root of "ever-flowing nature"
(see also Creators of Mathematical and Computational Sciences, Ravi Agarwal, Syamal Sen, Springer, 2014, p. 57).

The Pythagorean prayer addresses the sacred nature of the Tetractys: "Bless us, divine number, thou who generated gods and men! O holy, holy Tetractys, thou that containest the root and source of the eternally flowing creation! For the divine number begins with the profound, pure unity until it comes to the holy four; then it begets the mother of all, the all-comprising, all-bounding, the first-born, the never-swerving, the never-tiring holy ten, the keyholder of all" (cfr. the Kabbalistic Tree of Life). The Pythagorean oath also mentioned the Tetractys, resembling the (Kabbalistic) Hebrew Tetragrammaton (YHWH): "By that pure, holy, four lettered name on high, nature's eternal fountain and supply, the parent of all souls that living be, by him, with faith find oath, I swear to thee."
(see also Greek Philosophers as Theologians: The Divine Arche, Adam Drozdek, Routledge, 2016, p. 55).

The Tetractys was also conceived to represent four Emanations and four planes. The first Emanation, the Monad, is the source of latent power and corresponds to a Geometric Point. The second Emanation occurs when the point moves thus producing a line. This Emanation is called Growth (Auxe). The third Emanation occurs when the line moves creating a surface or plane. This Emanation is called Skin (Khroia). The fourth and final Emanation is developed when the surface moves, generating a solid, called Body (Soma). The first Plane in the Tetractys was the Monad (one), and it corresponds to the virtue Wisdom. The second Plane comprised the Dyad (two) and the Triad (three), and it corresponds to the virtues Strength and Courage. The third Plane was comprised of the Tetrad (four), Pentad (five), and Hexad (six) and represented the virtue Beauty. The fourth Plane was comprised of the Heptad (seven), the Octad (eight), Ennead (nine), and the Decad (ten). The fourth Plane represented the virtue Justice. Beauty, Wisdom, Goodness, and the corresponding connecting properties, Love, Truth, and Trust, which are the Chaldaean Virtues all are correspondences of the Tetractys. Through the Emanations and Planes the universe was created in the Pythagorean system
(see also Geschichte unserer abendländischen Philosophie, Eduard Maximilian Röth, Bassermann, 1858, p. 824).

Although ten was called one of the perfect numbers by the Pythagoreans, meaning unity within zero or the symbol of Deity, of the Universe, and of man, seven was unique in their series of numbers because it has all the "perfection of the Unit - the number of numbers. For as absolute unity is uncreated, and impartite (hence number-less) and no number can produce it, so is the seven: no digit contained within the decade can beget or produce it". Seven is the number of the manifested (Limited) universe, while ten or twelve is the number of the unmanifested (Unlimited) universe. Pythagoras taught that seven was composed of the numbers three and four, explaining that "on the plane of the noumenal world, the triangle was, as the first conception of the manifested Deity, its image: 'Father-Mother-Son' (e.g. Egyptian and Christian Trinity); and the Quaternary, the perfect number, was the noumenal, ideal root of all numbers and things on the physical plane". Further, seven was called by the Pythogoreans the vehicle of life for it consisted of body and spirit: the body was held to consist of four principal elements, while the spirit or soul was in manifestation triple, comprising the Monad (The One, Beauty), intellect or essential reason (logos), and mind (nous). Seven therefore was considered the sacred number of life, and together with the circle and the cross it forms a triad of primordial symbols in Pythagorean philosophy
(see also Signs and symbols illustrated and explained, 12 lectures, George Oliver, 1857, pp; 207-208).

Related to the Tetractys is the 'γνομον' (Gnomon), a pair of recurring figures produced by moving regularly spaced points, enables all the geometric figures to be represented. A gnomon is a plane figure when added to a given figure, makes a larger figure of the same shape. Series of odd and even numbers can be geometrically represented as gnomons. The odd Gnomon generates all the odd numbers starting from the Monad or unity. Because it is symmetrical, it also generates the square and figures related to it. The sequence of odd gnomons can be represented by the odd numbers: 1, 3, 5, 7, 9, 11, 13, 15, 17, ... . With the gnomon with base one all odd numbers can be produced and it also produces square numbers. A square number is an integer that is the square of an integer. Square numbers are 1, 4, 9, 16, 25, ... of which the square root is a positive integer (natural number) 1, 4=2², 9=3², 16=4², 25=5². The shape of the growing gnomon of odd numbers always remains the same, so they represent definedness. The (odd) gnomon allows to obtain all the squares from one unit square, from the arithmetic series of odd numbers. The series of odd numbers was represented by the gnomon in the form of a right triangle 'Γ', the even numbers by the '=' sign and the circle or sun of Ra, as the symbol of perpetual movement, was represented by the circle With helpful use of the gnomon, one can find support for the conjecture that the sum of the first n odd numbers is n²
(see also Civilization or Barbarism: An Authentic Anthropology, Cheikh Anta Diop, Yaa-Lengi Meema Ngemi and Square numbers and Greek Philosophy, Reginald E. Allen, Simon and Schuster, 1991, p.8).

From the gnomon with base 2 one can produce all even numbers, which can be presented by a rectangular gnomon. Besides the square numbers we have the series of oblong numbers: 2, 6, 12, 20, 30, ... which is the succession of products of positive integers (6=2x3, 12=3x4, 20=4x5, 30=5x6). These numbers can be geometrically represented by the oblong gnomon which represents the series of even numbers. The even gnomon, generates the even numbers and rectangular figures. As the ratio of the sides of this gnomon change shape when it grows, it symbolizes undefinedness
(see also The Evolution of the Euclidean Elements, W.R. Knorr, Springer Science & Business Media, 2012, 143).

The discovery of the Golden Ratio or Sectio Divina (Φ=1.61803399... and φ=0.61803399), an irrational number with several curious properties, which appears frequently in geometry, is also attributed to Pythagoras. Two quantities are in the Golden Ratio if the ratio of the sum of the quantities to the larger quantity is equal to the ratio of the larger quantity to the smaller one. The division of a line into "extreme and mean ratio" (the golden section) is important in the geometry of regular pentagrams and pentagons. The Pythagorean Theorem is related to the Golden Ratio. The Golden Ratio or internal golden section (φ) and the external golden section (Φ) can be constructed starting from a right triangle (right-angled triangle), with a compass, where the hypotenuse is equal to 1/2 x sqrt(5). The Golden Ratio connects the right-angled triangle and the Pythagorean Theorem to the proportions of the pentagram. Each corner of a petagram is in itself a golden triangle. The Golden Ratio is also related to Fibonacci Numbers
(see also The Golden Ratio and The Fibonacci Numbers). The first two numbers in the Fibonacci sequence (0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...) are 0 and 1 (alternatively, 1 and 1), and each subsequent number is the sum of the previous two: x_n = x_n-1 + x_n-2. If a Fibonacci number is divided by its immediate predecessor in the sequence, the quotient approximates Φ and the bigger the pair of Fibonacci Numbers, the closer the approximation. The Golden Ratio can be found in the cosmos and in nature (e.g. golden spiral and plant growth patterns) and was considered a Divine Ratio. It's use in architecture (e.g. the Parthenon) and geometry was meant to reflect the divine proportions of the universe and nature
(see also The Golden Ratio, M. Livio, Random House LLC, 2008 and Mathematics of Harmony: From Euclid to Contemporary Mathematics and Computer Science, A. Aleksei Petrovich Stakhov, World Scientific, 2009, p. 39 and A Cultural History of Physics, K. Simonyi, CRC Press, 2012, p. 54).

The second study after mathematics is music, the ancient name for the mathematical study of ratios. To Pythagoras music was one of the dependencies of the divine science of mathematics, and its harmonies were based on mathematical proportions. The Pythagorean musical system was based on the ratio's found in the Tetractys, as the rows can be read as the ratios of 4:3 (perfect fourth), 3:2 (perfect fifth), 2:1 (octave), forming the basic intervals of the Pythagorean scales. The key to the Pythagorean harmonic ratios is therefore hidden in the Pythagorean tetractys. The tetractys is made up of the first four numbers -1, 2, 3, and 4-which in their proportions reveal the intervals of the diapason (octave), the diapente, and the diatessaron. A division of the octave into two tetrachords separated by a tone is the basis of the diatonic scale, dia tonic, having a tone between the two tetrachords which are then referred to as diatonic tetrachords. A two octave disdiapason was called the Greater Perfect System. The number series 4 : 6 : 8 : 9 :12 :16 is often associated with the greater perfect system and the theory of proportion. The intervals between members of this series are fifth, fourth, tone, fourth and fourth. These intervals give the tuning for the fixed intervals of the tetrachords of the greater perfect system
(see also The Pythagorean Theorem: A 4,000-year History, Eli Maor, Princeton University Press, 2007, pp. 18-19)

The musical harmonies were also used in Pythagorean cosmology as sidereal harmonics. It was also said that of all men only Pythagoras heard the music of the spheres. In the Pythagorean concept of the music of the spheres, the interval between the earth and the sphere of the fixed stars was considered to be a diapason-the most perfect harmonic interval. The allowing arrangement is most generally accepted for the musical intervals of the planets between the earth and the sphere of the fixed stars: From the sphere of the earth to the sphere of the moon; one tone; from the sphere of the moon to that of Mercury, one half-tone; from Mercury to Venus, one-half; from Venus to the sun, one and one-half tones; from the sun to Mars, one tone; from Mars to Jupiter, one-half tone; from Jupiter to Saturn, one-half tone; from Saturn to the fixed stars, one-half tone. The sum of these intervals equals the six whole tones of the octave
(see also Absolute Music: The History of an Idea, Mark Evan Bonds, Oxford University Press, 2014, p. 25 and Celestial Treasury: From the Music of the Spheres to the Conquest of Space, Marc Lachièze-Rey, Jean-Pierre Luminet, Bibliothèque Nationale de France. Paris Cambridge University Press, 2001, p. 61).

The 47^th proposition of the first book of Euclid or The Pythagorean Theorem

The third study is geometry, the study of the three dimensions: length, width, and height. Geometry and geometric figures played an important role in Pythagoreanism. Pythagoras is considered to be the father of the so-called 47^thproblem which Euclid (fl. 300 BCE) describes in his Elements for finding the length of the hypothenuse of a right angle triangle in which the sides are 3, 4, and 5 - all whole numbers - and which is also known as 'the Egyptian string trick'. Euclid in the Elements provided two proofs for the Pythagorean Theorem; in Book I with proposition 47 (I.47) and Book VI a more general proof with proposition 31 (VI.31). Proposition I.47 can be considered to be a special case of proposition VI.31. The Pythagorean theorem deals with three pairs of correspondingly similar shapes. The first component in a pair is a right triangle, the second can be any shape. It's taken to be a square in I.47 and an arbitrary polygon in VI.31. In proposition VI.31 Euclid in general stated that 'In right-angled triangles the figure on the side opposite the right angle equals the sum of the similar and similarly described figures on the sides containing the right angle'. The only constraint imposed on the second component is that its shape be fixed and be related in some manner to that of the first component in such a way that both change proportionally under a similarity transformation. Simply the theorem states that each external figure is proportional to the internal triangle which is attached to the same side.

The essence of Pythagoras's theorem is similarity and scaling and it can be used with any shape and for any formula that squares a number. It is based on the principle that any given area formula works for all similar shapes, where "similar" means "zoomed versions of each other". In a normal Euclidean space, the length of a vector is determined by a Pythagorean sum of the components. The Pythagorean Theorem depends on the assumptions of Euclidean Geometry and doesn't work on spheres or globes. Euclidean geometry is the study of geometry that satisfies all five of Euclid's axioms and postulates. The five postulates of Euclidean Geometry define the basic rules governing the creation and extension of geometric figures with ruler and compass. Together with the five axioms (or "common notions") and twenty-three definitions at the beginning of Euclid's Elements, they form the basis for the extensive proofs given in the Elements. The Postulates talk about straight lines, circles, right angles and parallel lines. The Axioms are about relationships; what does equal mean, how do you add or subtract things, and so on. Euclidean Geometry as such is based on a set of 'principia neutra', which must be accepted from within the system although their value when seen from outside the system is arbitrary. In deductive reasoning, nothing can be deduced if nothing is assumed. Axioms and postulates are the basic assumptions underlying a given body of deductive knowledge. They are (to be) accepted without demonstration, so at the core of any deductive thought system, there is always assumption and belief in some basic principle(s) which are being derived from 'nothing'. The chain of logical reasoning and causation ends here. At the core of a rational system, there is always intuition
(see also Math Through the Ages: A Gentle History for Teachers and Others, W. P. Berlinghoff, F. Fernando Quadros Gouvêa, MAA, 2004, p. 143 and Mechanics Over Micro and Nano Scales, S. Chakraborty, Springer, 2011, p. 68).

- The Pythagorean Pentagram with the UGIEIA or Hygieia -

The ancient Pythagorean pentagram, a symbol of mathematical perfection, represented the dominion of the Spirit over the four elements of Nature. The five point star symbolizes the five elements of earth, air, fire, and water with the top point symbolizing aether or Spirit. The pentagram or pentad's symbolism can be directly related to the Divine Proportion and the value of Φ (Phi). Each corner of the pentagram is also a golden triangle. The figure also contains five golden gnomons, made by joining two non-adjacent corners to the central pentagon. The letters surrounding a Pythagorean pentagram are upsilon, gamma, iota, epsilon, iota, and alpha and they spell UGIEIA (often rendered Hygieia), which means health. Hygieia was a daughter of the god of medicine, Asclepius. Hygieia was used as a greeting among the Pythagoreans. The Pentemychos or Heptamychos ('of five sanctuaries'), a cosmogony written by Pythagoras' teacher and friend Pherecydes of Syros (6^th century BCE) uses the pentagram. Pherecydes taught his philosophy through the medium of mythic representations. These works form a bridge between mythic and pre-Socratic philosophy. The pentagram was the 'island' or 'cave' where the first pre-cosmic-offspring had to be put in order for the cosmos to appear: 'the divine products of Chronos' (time) seed (Ophioneus, Cthonie, Eurynome, Echidna and Callirhoe), when disposed in five recesses, were called 'Pentemuxos'. Once Chronos' offspring were housed here, the ordered cosmos began to form. After the Light, the ordering principle, appears, a cosmic battle takes place. On one side is Kronos (ordered time) and on the other is the offspring of Chronos, led by Ophioneus. Ophioneus is depicted as a multi-headed snake ("ophis") or dragon. Kronos is victorious and the ordered cosmos can appear. He orders the offspring of Cronos out from the cosmos to Tartaros. The Pentemychos is in Tartarus as the gate to the underworld. Pherecydes' contribution to the early Presocratic thought is the denial of ex nihilo creation, cosmos self-creation and the the eternal nature of the first principles. The notion of the doctrine of metempsychosis (referring to transmigration of the soul) is accredited to Pherecydes, and thereby giving the first teaching of the immortality of the soul
(see also Space and Time in Ancient Greek Narrative, A. C. Purves, Cambridge University Press, 2010, p. 100-108 and The Mother of the Gods, Athens, and the Tyranny of Asia, M. H. Munn, University of California Press, 2006, p. 48-51 and A study of the doctrine of metempsychosis: in Greece from Pythagoras to Plato, H. Strainge Long, Princeton University, 1948, p. 14 and 69).

The fourth study in this system is that of astronomy, the study of three-dimensional objects in a fourth dimension, or motion in space-time. Astronomy embraces each of the prior three studies and a fourth (motion in time), with four representing the four primary elements of physical reality: fire, air, water and earth.

Later on Aristotle would stand in the Ionian tradition and Plato would follow the Italiote tradition. Pythagoreanism, with its emphasis on attuning the soul to a vision of the deepest level of reality through the study of mathematics and proportion, lies at the heart of Plato's educational program described in the The Republic (380 BCE)
(see also Foundations of Education, A. C. Ornstein, D. U. Levine, Cengage Learning Inc., 2008, p. 70 and Ideal and Culture of Knowledge in Plato, Karl-und-Gertrud-Abel Stiftung. Tagung, Franz Steiner Verlag, 2003, p. 11 and Plato's Cretan City: A Historical Interpretation of the Laws, G. R. Morrow, Princeton University Press, 1993, p. 573-574).

Pythagorean symbols would survive long after the Pythagorean brotherhood had disappeared. Symbols also tend to change through the ages. The pentagram was used as a Christian symbol for the five senses, and if the letters S, A, L, V, and S are inscribed in the points, it can be taken as a symbol of health (from Latin salus). Gnosticism considered the Pentagram to be the Microcosmic Star, or the Word of God made flesh
(see also The Gnostic Jung and The Seven Sermons to the Dead, Stephan A. Hoeller, Quest Books, 1982, p. 179). Medieval Christians believed that the 'pentalpha' symbolizes the five wounds of Christ. The pentagram was believed to protect against demons. In late antiquity the pentagram would be used as a symbol by the Gnostics. The Gnostic Pentagram is the human figure with four limbs, and one unique apex which is the head. When the superior point of the Pentagram is aiming upwards towards the sky, it represents the Savior of the world. The sign of the Pentagram is also called the sign of the Microcosm. It represents what the Kabbalist Rabbi Hayyim ben Joseph Vital (1543-1620 CE) in the book Zohar calls the Macroprosopos or First Adam (Adam Kadmon) as opposed to the Microprosopos or Adam on earth
(see also the Vitruvian man). Adam Kadmon is comparable to the Anthropos of Gnosticism and Manichaeism. In Alchemy and Kabbala the Platonic elements of the Pythagorean pentagram are combined with the three parts which constitute man (body, soul and spirit) into mercury (water and spirit), sulphur (fire and soul) and salt (earth and body). The four Platonic elements and the three principles reside in every living and non-living substance, but in different proportions.

Sophists in Greece were a category of teachers who specialized in using the tools of philosophy and rhetoric for the purpose of teaching Arete (excellence) or virtue, predominantly to young statesmen and nobility. Arete was also the goddess or daimona of virtue, excellence, goodness and valour. The sophists of the fifth century BCE created a "Sophistic Enlightenment", which also included Socrates (ca. 469-399 BCE), but several of them were condemned for their disregard of tradition. In the fourth century BCE the rhetoric techniques of the sophists were adopted by various unscrupulous characters, giving sophistry the bad name it still has for clever (but fallacious) verbal trickery (The Sophistic Movement, G. B. Kerferd, Cambridge University Press, 1981 and The Older Sophists, H. Diels, R. Kent Sprague, Hackett Publishing, 2001).

Protagoras (ca. 490-420 BCE) is generally regarded as the first of the sophists. Others sophists are Gorgias (483-375 BCE), Prodicus (ca. 465-ca. 395 BC), Hippias (late 5th century BCE), Thrasymachus (ca. 459-400 BCE), Lycophron, Callicles (ca. 484-late 5^th century BCE), Antiphon (480-411 BCE), Diagoras of Melos (5^th century BCE), and Cratylus. Protagoras, Gorgias, Hippias, and Prodicus are collectively known as the Older Sophists, which are mainly known from the Platonic dialogues. They lived during the reign of Pericles (ca. 495-429 BCE), also known as the Golden Age of Athens.

Protagoras (ca. 490-420 BCE) put forward that judgments and knowledge are in some way relative to the person judging or knowing and therefore postulated that man is the measure of all things. He rejected the realist view of the existence of universals and extramental absolute truth. Two works are attributed to Protagoras: Alêtheia (On truth or Refutations) and On the Gods. His teachings can be divided into Orthoepeia (the study of the correct use of words), the Man-measure statement (the notion that knowledge is relative to the knower), and Agnosticism (the claim that we cannot know anything about the gods). In his work Alêtheia (On truth) Protagoras's central idea was that human beings are measures or 'criteria' of what is true (homo mensura). His 'homo mensura' statement reflects the relativity of all human knowledge, and the impossibility of penetrating beyond the appearances of things. His "πάντων χρημάτων μέτρον’ ἄνθρωπον εἶναι" (Plato, Theaetetus, 152a and Cratylus, 385E) meant that "man is the measure of all use things". It makes man as 'homo faber' the measure of all things in a pure means and end logic (H. Arendt, 1998, p. 157-158). Protagoras does not make any distinction between knowledge (episteme) and opinion (doxa). He started his Alêtheia with " The individual human being is the measure of all things, of what is, that it is, of what is not, that it is not" ("Anthropos metron panton, kai ton syton, kai ton me onton") as opposed to Parmenides (early 5^th century BCE) who rejected the existence of "what is not". Protagoras postulated the relativity of knowledge, while Parmenides had postulated the relativity of reality. He cited the example of a wind which may seem warm to one person and cool to another. It is not necessary, he urged, to say that one view is true and the other false. Each may be true for the person concerned. The view of Protagoras on alêtheia (truth) is closely related to the modern theory of existential truth (speculation versus revelation), although it is often referred to as extreme relativism. The relativity of viewpoints however is not the same as relativism with regard to absolute ethical standards and tanscendent first principles. Relativism with regard to absolute standards is the synchronous presence within one person of believing in a(n absolute) principle, either immanent or transcendent, and postulating an excuse for not needing or not being capable to adhere to the absolute principle. The relativity of viewpoints of Protagoras can be regarded as amoral with regard to an absolute ethical stadard, but the second position is immoral as it is to be considered as opposition to morality. Protagoras refused to view the material world as mere illusion as opposed to Parmenides of Elea (early 5^th century BCE) and Plato (424/423-348/347 BCE). A consequence of Protagoras's agnosticism and relativism was that laws (legislative and judicial) were considered to be things which evolved gradually by agreement (brought about by debate in democratic assemblies) and thus could be changed by further debate. This position implied that there was a difference between the laws of nature (absolute) and the customs of humans (amenable to change). Plato in a response to this position began the search for transcendent forms or knowledge which could somehow anchor moral judgment
(see also The Human Condition, Hannah Arendt, University of Chicago Press, 1998)

Gorgias (483-375 BCE) wrote On the Nonexistent or On Nature, the Apology of Palamedes, the Encomium on Helen, and the Epitaphios or Athenian Funeral Oration. In On the Nonexistent or On Nature Gorgias rejected that "things exist". He opposed speculative philosophy of being and postulates an extreme scepticism. His nihilistic argument is a 'trilemma': nothing exists and even if existence exists, it cannot be known and finally even if it could be known, it cannot be communicated. The mental representation is different from the thing itself, which in itself remains unknown. The operation of the mind (intellection) for Gorgias is fundamentally distinct from what happens in the real world. For Gorgias it is logos (reason) and logos alone which is the proper object of our inquiries, since it is the only thing we can really know. The search for (absolute) truth is futile as there exists only opinions which can be directed by rhetoric. For Gorgias the only alternative for violence (war) is rhetoric, by which means the word rules over man. The orator has to adapt himself to a (particular) situation and inspire his audience in order to convince it of his viewpoint(s).

Hippias (late 5th century BCE) invented the quadratix, which would solve the problem of squaring the circle if it could be mechanically described. From Hippias originated the idea of natural law as the foundation of morality, distinguishing nature from the arbitrary conventions of humans, differing according to the different times or regions in which they arise, imposed by arbitrary human enactment, and often unwillingly obeyed. Hippias held that there is an element of right common to the laws of all countries and constituting their essential basis. He held also that the good and wise of all countries are naturally akin and should regard one another as citizens of a single state, which is cosmopolitanism. The Older Sophists still tended to agree with and follow generally accepted moral codes, even while their more abstract speculations undermined the epistemological foundations of traditional morality.

Thrasymachus (ca. 459-400 BCE) put forward that justice is nothing but the advantage of the stronger. This seems to support the view that moral values are socially constructed and are nothing but the reflection of the interests of particular political communities. Callicles (ca. 484-late 5^th century BCE) also put forward that the institutions and moral code of his time were not established by gods but by men who naturally were looking after their own interests.

Lycophron is generally believed to have used the theory of the social contract to set limits to the scope of law. In the Sophist tradition, the term physis (nature) stood in opposition to nomos, meaning "law" or "custom", in the debate on which parts of human existence are natural, and which due to convention.

The Pre-Socratic philosophers had increasingly explained natural phenomena in terms of natural laws without the need for divine intervention. The sophist Diagoras of Melos (5^th century BCE), who substituted the active powers of nature for the activity of the gods, was regarded as an atheist. Like Socrates, he gave offence by his views concerning the worship of the national gods as he spoke out against the Greek religion, and criticized the Eleusinian Mysteries. The Athenians therefore accused him of impiety, and he was forced to flee the city.

- Scuola di Atene by Raphael in the Vatican Stanza della Segnatura -
In the center on the left stands Plato holding his Timaeus besides Aristotle holding his Nicomachean Ethics
Plato points upwards to the transcendent world of the Ideas,
while Aristotle points downward to the immanent world of Forms and the Earth.

The classical period of Greek philosophy starts with Socrates (ca. 469-399 BCE) and his pupil Plato (424/423-348/347 BCE). The different Pre-Socratic philosophical systems of Ionia and the West (Italiote) came into contact with each other in Athens. Pre-Socratic philosophy had run into a blind alley and had become mere sophisms, from which it could only escape by trying back. All the scientific schools end at Athens, and it was Socrates who concluded that the questions they had raised could only be met by making a fresh start from another point of view. Plato's dialogues are the most comprehensive accounts of Socrates to survive from antiquity, because Socrates himself left us no writings. It is this Platonic Socrates who also lends his name to the concepts of Socratic irony and the Socratic method, or elenchus. Socrates made important contributions contribution to the field of ethics, epistemology and logic
(see also Socratic, Platonic and Aristotelian Studies, G. Anagnostopoulos, Springer, 2011 and Order and History, Volume 3, E. Voegelin, University of Missouri Press, 2000).

Socrates, Plato, and Aristotle (384-322 BCE) were the most influential of the ancient Greek philosophers, and they focused their attention more on the role of the human being than on the explanation of the material world by the Pre-Socratic philosophers. Plato and Aristotle were also the first who developed a philosophy which was based on abstract eternal and perfect concepts instead of principles releated to physical reality. The essence of their philosophy was non-physical, which gave them more freedom to develop their metaphysics and logic. Plato thought of his concepts as "forms" existing in another world, metaphysically, Aristotle saw them as concepts, categories of understanding in this world. Plato and Aristotle's doctrines contrast in the concepts of reality, knowledge at birth, and the mechanism to find the truth
(see also Aristotle and the Problem of Concepts, Gregory Salmieri, dissertation, University of Pittsburgh, 2008, p.57). Both wanted to grasp reality by means of reason, which is to be able to "give reasons", or "give an account" (logon didonai) and by means of dialectic reasonig to give an acount of something's being or essence: λόγος τῆς οὐσίας (logos tes ousias) or "ratio substantiae"
(see also Sources of the Self: The Making of the Modern Identity, Charles Taylor, Cambridge University Press, 1989, p.121 and New Essays on Plato and Aristotle (RLE: Plato), Renford Bambrough, Routledge, 1965, p.22)

The essence of the Platonic and Aristotelian philosophical traditions have occupied the Western intellectual tradition for the past 2500 years. Rationalism - knowledge is a priori (comes before experience) and Empiricism - nowledge is a posteriori (comes after experience). Aristotle, found the universal in particular things, which he called the essence of things, while Plato finds that the universal exists apart from particular things, and is related to them as their prototype or exemplar. For Aristotle, philosophic method implies the ascent from the study of particular phenomena to the knowledge of essences (growth, potentiality), while for Plato philosophic method means the descent from a knowledge of universal Forms (or ideas) to a contemplation of particular imitations of these. For Aristotle, "form" still refers to the unconditional basis of phenomena but is "instantiated" in a particular substance. In a certain sense, Aristotle's method therefore is both inductive and deductive, while Plato's is essentially deductive from a priori principles. Plato therefore was a creator, Aristotle an observer and interpretor. For Aristotle "nothing is in the mind that wasn't first in the senses". Plato based his Idea's theory on the concept of representation of reality in the cave throught shadows and on the passions of the Psyche (thymos psychis), on enthousiasm or jubilation and on extatic mania (methexis or unification with the Divine or "génoi oios éssi, mathón"). He needed inspiration to express all the above. In the contrary Aristotle needed Ataraxia (serenity) and Entelechia (assiduity) to interpret scientifically the World. Summarized, at least five contrasts can be found between Platonic and Aristotelian philosophy: vita contemplativa versus vita activa, mundus intelligibilis versus mundus sensibilis, transcendence versus immanence, eternity versus time, mystical unity versus rational-cum-empirical plurality. Both Plato and Aristotle developed a different view on the probem of universals and body and soul.

Throughout European philosophy and religion both Plato (424/423-348/347 BCE) and Aristotle (384-322 BCE), who was a student of Plato, left their mark. Plato suggested that man was born with knowledge, Aristotle argued that knowledge comes from experience. It is the Platonic ideal to turn away from mortality, vulnerability, contingency and mutability of the worldly appearances and to search for unchanging stability, clarity and precision. The "via Platonicorum" begins and proceeds "ex rationibus intelligibilibus", and thus thinks in terms of the inherent independence of the separate substances, while the "via Aristotelica" proceeds "ex rebus sensibilibus". Plato founded the Platonic Academy in Athens, while Aristotle founded the Lyceum which evolved into the Peripatetic school.

Socrates (ca. 469-399 BCE) is on of the most important philosophers in European history. However, because Socrates did not write anything, all our information about him is second-hand the only extant show contradictions and do not agree which leads to Socratic problem. Most of what we know about Socrates is found in the writings of Plato (424/423-348/347 BCE) and Xenophon (ca. 430-ca.350 BCE). The main sources for the historical Socrates are the Sokratikoi logoi (Σωκρατικὸς λόγος), or Socratic dialogs in the dialogs of Plato and the Socratic works of Xenophon in which characters discuss moral and philosophical problems. Socrates is believed to have studied the speculations of the Ionians and the Atomists about the nature of the world, but had been disappointed by them and so had turned to the study of man himself. Socrates was predominantly interested in ethics (virtue) and he would change the focus of Greek philosophy from the outside world to the condition of humankind. With Socrates, Greek philosophy moved away from a cosmological to a anthropological point of view. No longer was the cosmos the central theme of Greek philosophy, but man himself. hewould use his Socratic method to create a scientific foundation for morality and and the validity of principles as a standard for morality. While the sophists had used human reason to dismantle the foundations of traditional Greek morality, Socrates would use human reason to build a new new more rational moral philosophy. Contrary to the sophists, he believed that there were objective moral standards which could be discovered. For Socrates there were right and wrong answers to moral questions that went beyond mere opinion and popular sentiment. The good human life of Socrates is one lived in the light of reason or a rational knowledge of the good.
(see also Greek Thought: A Guide to Classical Knowledge, Jacques Brunschwig, Pierre Pellegrin, Harvard University Press, 2000, p. 102 and Moral Education and Development, Doret J. de Ruyter, Siebren Miedema, Springer Science & Business Media, 2012, p. 84).

His avowed purpose was "to fulfill the philosopher's mission of searching into myself and other men". For Socrates self-knowledge is the sufficient condition to the good life. He identified knowledge with virtue. If knowledge can be learned, so can virtue. Thus, virtue can be taught. For Socrates the unexamined life is not worth living. One must seek knowledge and wisdom before private interests. Knowledge is sought as a means to ethical action. What one truly knows is the dictates of one's conscience or soul: the philosophy of the Socratic Paradox
(see also Socrates: The Public Conscience of Golden Age Athens, J. Lim, The Rosen Publishing Group, 2005 and Socrates: a life examined, L. E. Navia, Prometheus Books, 2007).

Socrates was not a systematic philosopher and was content to teach mainly by informal discussion, using the Socratic method of feigning ignorance and asking questions of people so as to expose their own lack of real knowledge. He makes use of the dialectic method of the Sophists, though with him this method is always used in the service of the truth. The Socratic Method assumes a trust in reason and objective truth and emphasizes that one must, in acquiring knowledge, begin by being humble before reality. Socrates taught that every person has full knowledge of ultimate truth contained within his soul and needs only to be spurred to conscious reflection in order to become aware of it. As in the γνωθι σεατον of Oracle of Delphi at the Temple of Apollo. In Plato's dialogue Meno Socrates guides an untutored slave to the formulation of Pythagorean theorem, thus demonstrating that such knowledge is innate in the soul, rather than learned form experience. Socrates described the soul not in terms of mysticism but as "that in virtue of which we are called wise or foolish, good or bad". In other words, Socrates considered the soul to be a combination of an individual's intelligence and character.

The philosophy of Socrates was a reaction against the principles and relativism of the sophists. The sophists had challenged the foundations of Greek society, which had been built on the religion and customs of Greece. The sophistic theory of the relativity of knowledge was that all ideas and truths were relative to the individual who perceived them (homo mensura), which lead to the doctrine of conventionalism and individualism. For the sophists nomos (human law or custom) was more relevant and important than phusis (nature) or the Gods. Socrates would use a system of induction, definition, and dialectic argument leading to the clarification of ideas, and from this the establishment of a new basis for real or certain knowledge and morality. Socrates uses inductive reasoning in order to get from the particular (situation) to defining the general concept and defining the true essentials of virtue. Socrates starts with examining particular cases, reworking his definition of an idea as he goes, until he gets to a valid definition or sometimes only reaching aporia. Socrates began his inquiries with ideas and not with things, and the consequence was that he completely reversed the point of view from which the study of philosophy began. Instead of looking primarily at the external world he challenged his fellow man to discover in his individual ideas the contradictions which he had held to, and from this he compelled his opponent either to admit his own confusion or to reconstruct his view of knowledge. He tries to answer the question 'Wat is X (really)?' and the valid answer should be X is (certainly) Y, where X is called the definiendum and Y is the definiens which defines the definiendum. In his Socratic method he first questions his opponent about the nature or definition of a concept. Feigning ignorance, Socrates uses irony (εἰρωνεία) to give his opponent the feeling he is with him and eager to learn. Next the defense of the point of view of his opponent is questioned, which leads him to contradict himself in some way, thus weakening the defender's point. Socrates then leads his opponent through a series of elenchi (ἔλεγχος) or refutations of his point of view. After a while his opponent has to admit that he does not know what the concept is, leading to aporia (ἀπορία). It is only after the false opinions have been refuted the quest for the true definition can start. The correct definiens is the one that applies to all and only the instances of the definiendum, thereby creating a class which contains and delimits all particular instances of the definiendum defined by definiens. The early Socratic dialogs of Plato were often called his 'aporetic' (ἀπορητικός), because they typically ended in aporia. The Euthyphro (Ευθυφρων) is an example of an 'aporetic' dialog between Socrates and Euthyphro on the meaning of piety. According to Socrates getting to general moral concepts or principles was possible by applying the Socratic method. The Socratic method was meant to provide a rational foundation of the moral values of Greek society in order to create a reference for the individual to live by. However the validity of the definitions and moral standards remained valid only within the confines of the society in which they existed, it did not create (new) universal moral standards as such. In other words no moral first principles were created, only existing principles could be defined properly. In addition the problem remains how to be sure to reject faulty definitions and to be certain to know finding the right definition. This problem would become known as Meno's paradox, which contains the paradox of inquiry and the paradox of discovery. The paradox of inquiry means you can't come to know something that you didn’t already know. An inquiry never produces new knowledge, but only recapitulates things already known. This would lead to the Platonic 'Doctrine of Recollection' or anamnesis. Socrates describes his method as maieutics (midwifery, ἡ μαιευτικὴ τέχνη), because he induces his opponent to formulate or 'give birth to' latent concepts which he is unaware of (anamnesis). The possibility of a well founded non-relativistic morality depended only on knowledge of definitions. If you found out what was right, you would (automatically) do what was right. Knowing a moral definition was considered necessary and sufficient for moral behavior. If one knew what was right, one would do what was right, as virtue was based on knowledge of the right (moral) definitions leading to the traditional kalokagathia (καλοκαγαθία) or the ideal or perfect man. This is called Socratic intellectualism or determinism. Immorality for Socrates was the result of lack of knowledge, as a man having wisdom (φρόνησις) would always act morally
(see also Routledge History of Philosophy Volume I: From the Beginning to Plato, C. C. W. Taylor, Routledge, 2003, p. 225 and The Search for Certainty, W.W. Spradlin, P.B. Porterfield, Springer Science & Business Media, 2012, p. 72 and Socratic Definitions and Virtue in the Cave: Moral Inquiry in Plato's Meno, Roslyn Weiss, Oxford University Press, 2001, p. 53 and Meno, Plato, Meno's paradox, 80d-e and Theaetetus, Plato, Maieutics, 148e-151d).

Plato (424/423-348/347 BCE) was one of the leading Greek philosophers and his theory of the transcendent Ideas is the basis of his philosophy. He would develop the Theory of Forms and the 'Doctrine of Recollection' or anamnesis. Plato defends a clear ontological dualism in which there are two types of realities or worlds: the sensible world and the intelligible world or, as he calls it, the world of the Ideas. The Sensible World is the world of individual realities, and so is multiple and constantly changing, is the world of generation and destruction; is the realm of the sensible, material, temporal and space things. On the contrary, the Intelligible World is the world of the universal, eternal and invisible realities called Ideas (or "Forms"), which are immutable and do not change because they are not material, temporal or space. Plato explained the relation between the reltatio between the sensible world and the world of the Ideas in the Allegory of the Divided Line. Ideas can be understood and known; they are the authentic reality. According to Plato The Ideas are hierarchically ordered; there are different types and they do not have all the same value. The way to understand the ideas is to start with beauty and by recognizing what all beautiful things share in common. By starting from perceived beauty we move towards true wisdom, which is knowing Beauty itself. Beauty, for Plato, is the easiest place to start down the road toward True Knowledge and the ultimate Form of the Good. In The Republic (Πολιτεία) Plato in the analogy of the sun would use the sun as a metaphor for the nature of reality and knowledge concerning it. In the Allegory of the Cave (The Republic) Plato deals with human ignorance and people who are unable or unwilling to seek truth and wisdom (ἡ τοῦ ἀγαθοῦ ἰδέα)
(see also Plato and Platonism, J. M. van Ophuijsen, Catholic University of America Press, 1999 and Plato and Platonism, W.r Pater, Echo Library, 2006 and Dialogues of Plato: Translated Into English, with Analyses and Introduction, B. Jowett, Cambridge University Press, 2010 and Plato, Summary of his thought);

In the Symposium (360 BCE) Plato would give his definition of philosophy as part of his theory of desire. What we all love, according to the character Diotima, is the good or in other words we want good things to be ours forever. In the Symposium Plato discusses his view on friendship and Eros, which would later become known as "Platonic love". In the Symposium the character Diotima of Mantinea puts forward that Eros is the son of "resource and need" or in other words longing and destiny. In the Symposium Plato views eros as connected not only to sexual love, but also with philosophizing and to our desires for beauty, wisdom, and even immortality. Plato uses the term eros to mean desire in general, connected to but distinct from both human sexuality and rationality. Eros is an intermediary between our mortal condition (need) and what is divine and immortal (destiny). Philosophy therefore is being aware of one's need for the divine and immortal and from there the desire of directing one's thoughts towards this higher destiny. Eros is the intense desire for the eternal possession of the good (in which happiness consists) that dominates our whole life and has as its specific erotic form the search for immortality through procreation in beauty in order to get as near as possible to ownership of the good. Those who are able to follow a philosophical way of life might be able to contemplate the Good or Beauty itself. This leads to one of the fundamental tenets of Platonism, which is the assertion that 'virtue is knowledge'
(see also Plato's Symposium, R. Hunter, Oxford University Press, 2004 and Plato's Stepping Stones: Degrees of Moral Virtue, M. Cormack, Continuum, 2006, p. 96).

- Form of Good -

Plato developed a Theory of Forms in which he argued that non-physical (but substantial) Forms (εἶδος) represent the most accurate reality. The Theory of Forms was meant to deal with the problem of permanence and change. The Platonic solution to the problem of permanence and change was to split up existence into two realms: the changing material realm and the unchanging transcendent realm of Forms. These Forms are both aspatial (transcendent to space) and atemporal (transcendent to time). The Forms are the only objects of study that can provide true knowledge (Επιστήμη) as opposed to opinion (δόξα). The difference between true knowledge and opinion is made by Plato in several of his dialogs. For Plato "episteme" (knowledge) is "alethes doxa" (true opinion), supplemented by an appropriate "logos" (account, reason, word). Doxa is not only opinion, but also the faculty or capacity to produce opinion. Doxa is the state of mind of the non-philosopher (the lover of opinion, philo-doxos), and its object is the perceptible world of becoming (e.g. Allegory of the Cave), which is both to be and not to be, and things that are copies of the Forms in the world of reality. In contrast, episteme is not only knowledge as a consequence of cognition, but also the faculty to produce knowledge. It is a state of mind of the philosopher (the lover of wisdom, philo-sophos), and its object is the world of the Forms itself, which really is. Although a doxa (opinion) can be true, it is not anchored down in truth itself and therefore it is only a (floating) conjecture. Every level of knowledge is related to the level of reality which is being studied, the object of study defines the validity of knowledge (Platonic objectivism). The relation of Being to Becoming is the same as Knowledge is to Meaning. True knowledge deals with Being, while opinion deals with the world of becoming. Unlike Parmenides (late sixth or early fifth century BCE) Plato has the changing world participate into the world of being. Through communion (koinonia), participation (mehtexis) and presencing (parousia) the Forms are immanent in their objects. Paradigm (paradeigma), copy (mimesis) and image (eijkon) relate to the formal transcendence of the Forms. Objects in the surrounding world are the earthly copies (eikones or homoiomata) of the heavenly prototypes, where eikon represents the object, whereas homoioma emphasizes the similarity. Plato uses his theory of anamnesis (ἀνάμνησις) and the immortality of the soul to explain the path from mere doxa towards true knowledge. Plato discusses episteme and doxa in his dialogs Theaetetus (360 BCE) and Meno (380 BCE). The distinction between the world of the Forms from the sensible world is also discussed in detail in the Republic (Book V), and is essential for Plato's separation of the world of the Forms from the sensible world. The highest Idea or Form is the Form (or Idea) of the Good and this is the ultimate object of knowledge. The Form of the Good in Plato's system is also the One or Absolute Beauty. The One or the Good is the summit of existence and the source and destiny of all things, including the other Forms. All Forms are interrelated, and arranged in a hierarchy. All Forms together are the exemplary or formal cause and model (pattern) of Being from which the Demiurge (δημιουργός) or Reason as the efficient cause creates the orderly Cosmos out of chaotic matter (material cause). Reason also delivered a final cause in the creation of the Cosmos as the Demiurge desired to instantiate the good in the world, but of course due to the limitations of matter Reason did not succeed entirely as we can read in the Timaeus
(see also Plato's Theory of Knowledge, N. Gulley, GREENWOOD Publishing Group Incorporated, 1986 and The Participatory Turn: Spirituality, Mysticism, Religious Studies, Jorge N. Ferrer, Jacob H. Sherman, SUNY Press, 2008, pp. 84-85).

The method which Plato applies to arrive at truth is based on ancient Greek geometrical reasoning and the elenctic method or Socratic methodused by Socrates in Plato's early dialogues. The term "elenctic" is derived from the Greek word "elenchein", meaning to cross-examine or refute. Socrates in the Platonic dialogs tries to find a definition of an item (truth) through a dialogue with his interlocutors. For Plato truth unfolds during a philosophical debate (διαλέγεσθαι). For Socrates his dialégesthai were aimed at the correct interpretation of concepts and ordering those concepts into an hierarchy. Socrates connected dialectic with dialegein or sorting of things into their kinds by taking counsel with each other
(see also The Socratic Method: Plato's Use of Philosophical Drama, Rebecca Bensen Cain, Bloomsbury Publishing, 2007 and An Examination of Plato's Doctrines: Plato on Knowledge and Reality, Volume 7, I. M. Crombie, Routledge, 2012, p. 563).

Pythagoreanism, with its emphasis on attuning the soul to a vision of the deepest level of reality through the study of mathematics and proportion, lies at the heart of Plato's educational program described in the The Republic (380 BCE). Where Plato parted company with Pythagoras was in his overwhelming emphasis on the transcendent. For Pythagoras, the divine order is immanent in the cosmos, where it may be encountered; but Plato emphasized a transcendent metaphysic of forms or examples, only accessible to the purified intellect, divorced from the phenomena of nature. Plato's philosophy is a metaphysic of the transcendent; the Pythagorean philosophy is a metaphysic of the immanent order. Plato adopts the Pythagorean notion that number is the principle of order in the cosmos and life, but number as such to him is not yet a theion (divinity). It points at a purely intelligible Number which is a Form (eidos), no immanent principle of order within the objects, but a transcendent example. In either case, both Pythagoreanism and Platonism stressed an epistemology in which human beings (microcosm) can know the deep structure of the world (macrocosm) because of the mind's essential kinship with its archetypal structure. For Plato, strongly influenced by Pythagoras and the Eleatics, there is a real, Divine world of ideas "out there" or, as in Neoplatonism, "in here", a transcendent realm of Being, in which the things of this fluctuating world participate. Ideas are the unchanging aspects of a thing. The ontological difference between the world of becoming and the world of being was preluded by the views of Anaximander (ca. 610-546 BCE) and Parmenides of Elea (early 5^th century BCE), and finally synthesized by Plato. The world of being consisted of unchanging, inherently existing "ideas" (Forms), constituting the entities populating the world of becoming, radically separated from the former. With the ontology of the One by Plotinus (204/5-270 CE), this radical transcendence will be finalized. Self-sufficient and autarchic, the One is a "substance of substances"
(see also Pythagoras: His Lives and the Legacy of a Rational Universe, Kitty Ferguson, Icon Books Ltd, 2011, Ch. 8).

- Form of Good -

Plato in his philosophy maintains that degree of skepticism which denies all permanent authority to the evidence of sense. In essence, Plato suggests that justice, truth, equality, beauty, and many others ultimately derive from the Form of the Good. Plato, in Book VI of The Republic (380 BCE) uses the Sun as a metaphor for the source of "illumination", arguably intellectual illumination, which he held to be "The Form of the Good" his concept of the "summum bonum". The Sun makes physical objects visible and generates life on earth, the Good makes all other universals intelligible. The Form (or Idea) of the Good is the ultimate object of knowledge, although it is not knowledge itself, and from the Good, things that are just gain their usefulness and value. For Plato the divisions and qualities of the city-state are designed to be analogous to those of the human psyche and therefore The Republic deals with both politics and psychology. In the sixth and seventh books of The Republic both the Divided Line model and the Allegory of the Cave manifest the central idea of Plato concerning the structure of reality and how to achieve true knowledge. In these sections of The Republic, the relationship of copy to model is reflected on each level: from image-thinking to belief; from understanding to knowledge; from essence to intellection; and from the Idea of the Good to the Good itself. In The Republic, Plato builds an imaginary city-state as a contemplative model for the philosopher's "ascension to reality", producing in him "the image and likeness of God", it is this ascent that is called true philosophy. To achieve that end Plato outlines a threefold goal: To gain an understanding of the mind; to understand and experience the Idea of the Good and to achieve a vision of the Good itself. In Book VII of The Republic Plato puts forward his educational and scientific program based on the Socratic method or dialectical method and logic as the "ars definiendi". From ignorance man comes to the true definitions by means of dialectic reasoning and the application of logic. Logic for Plato does not exist independently of the metaphysical framework and is related to the objects of reality in order to avoid it from deviating into empty statements or conclusions. Pato uses three images to explain his ideas. The 'Divided Line' expresses Plato's hierarchical view of reality and wisdom. The 'Simile of the Sun' characterizes the act of apprehending highest truth in the form of the Good. In the 'Allegory of the Cave', Plato explains the ascend of the mind from illusion to true knowledge
(see also Archetypes of Wisdom: An Introduction to Philosophy, 8th ed., D. J. Soccio, Cengage Learning, 2011, p. 136-143).

- Divided Line -

Plato goes on to describe the levels of reality and knowledge with the device of the so-called "divided line" or Golden Ratio (Φ). Knowledge of the Forms is achieved via Dialectic, which questions assumptions and arrives ultimately to an unhypothesized/unassumed First Principle (the Good). The Divided Line explains the process of becoming a philosopher and learning the Truth in terms of divisions on a single line. The parts of the Divide Line are: imagination, belief (conviction) versus understanding (dianoia) and reason (nous). Relations among the subsections of the Divided Line follow the proportion(s) of the Golden Mean in a strict manner: ideas are to concepts as objects are to images, or going accross the two realms - ideas are to objects as concepts are to images
(see also Archetypes of Wisdom: An Introduction to Philosophy, 8th ed., D. J. Soccio, Cengage Learning, 2011, p. 136-138 and Plato and the Good: Illuminating the Darkling Vision, R. Desjardins, BRILL, 2004, p. 55-56).

Imagine a line cut into 4 sections, with the endpoints being A, B, C, D, and E. The line segment AB is the shortest of them and it represents the masses sitting at the back of the cave (Allegory of the Cave), believing that all there is to know in the world lies in those shadows that they see. A person's source of knowledge in the area AB consists of images, reflections, and shadows. All of these are distortions of real objects and cannot tell a person the truth about an object but allows for conjectures and generally inaccurate guesses. BC is the next segment and is a bigger than AB by a certain factor. It represents a person's knowledge as he gazes at the fire and comes to understand that the shadows are formed by figures going back and forth before the fire. Source of knowledge in this area includes real objects, so that while the reflection of a ball represents segment AB, the real ball represents segment BC. CD is the next segment and represents mathematical understanding. It is equivalent to a philosopher crawling out of the cave and perceiving sunlight for the first time. In terms of the ball example, what falls under this area is the concept of a perfect sphere that we hold in our heads when we perceive the ball. Segment DE, which is larger than CD by the same factor as BC is larger than AB, is the final segment and consists of philosophical understanding. It is at this stage that a philosopher gains understanding of concept-forms such as justice, goodness, and truth. The four sections of the Divided Line are grouped into two sections, one is governed by the Sun, and the other is governed by "The Good". The first two sections are governed by the sun because they are concerned with physical objects which can only be perceived with the light of the sun. This brings us to the Analogy of the Sun. Plato believed that of the five senses, sight was the most noble. His justification for this is that while in other senses, the process involves only two parts, a sensor and a sensed (for example, an ear and a sound), sight involves three parts; the seer, the seen, and the sun to provide light. For this reason, the sun is the noble entity which brings understanding when it comes to physical objects. In the same way, reason is noble because it requires a person to understand, the understood, and the good to make it possible for this understanding of the eternal forms to take place. That is why the last two segments of the Divided Line are governed by "The Good". There is a distinction between the first two segments and the last two segments as well, and the portion governed by the good is larger than the portion governed by the sun by the same factor as BC is larger than AB. From this, we can see that Plato believed there to be a difference between that which we perceive with our senses and that which we understand innately with our minds. Plato believed that those philosophers who understood the eternal forms could be rulers of a city or state because only they would truly understand concepts of justice and righteousness. What we see in the physical world is flawed, while the eternal forms are unchanging, pure, perfect, and absolutely beautiful. Plato also distinguishes between the hypotheton which defines and limits the realm of mathematics and the anhypotheton, which is the form of the good or the sun in the similes of the cave and the sun. In the Republic Plato mentions the process by which noesis moves from hypotheses to the anhypotheton. The way towards the anhypotheton passes through mathematics . Within the second, intelligible realm of the divided line, the lower level is assigned to the objects of mathematical science. The mathematician has to make use of figures perceptible to the senses as images of the nonsensible mathematical ontic forms, and with these sensible images he develops and illustrates his propositions. In so doing, he proceeds from postulates (hypotheseis) such as even and odd, straight and crooked, and the angles, and without rendering a theoretical account of these hypotheses by tracking down their ground and cause, he deduces from them his propositions and proofs. The higher level in the realm of the divided line is occupied by the eide (Forms) or ontic forms. Platonic and Socratic dialectic, the knowledge of the eide by means of logical thought, should proceed from the divine idea of the Good as the anhypotheton, in order to apprehend from there the eide in their divine origin and thus to behold them fully in their particular ontic forms. It is the divine idea, not the eide, that is the absolute, the anhypotheton. Plato transcends (mathematical) hypothesis by grounding his diamoetic activity in something anhypotheton (an unhypothesized beginning). Within human knowledge, scientific understanding corresponds to the mathematical ontic forms, while rational knowledge corresponds to the eide. Without having to take recourse to the perceptual aid of visible forms, the latter ascends from the hypothesis to the anhypotheton, the absolute Origin. Both types of knowledge, dianoia and episteme (or noesis in the narrower sense), are comprised under the broader term noesis and are contrasted with doxa. The Divided Line symbolizes Plato's ascent from the hypotheseis upward to the anhypotheton and moving beyond the illusory world of doxa
(see also Platonic Philosophy of Religion, A: A Process Perspective, Daniel A. Dombrowski, SUNY Press, 2012, p. 83 and Musings on the Meno, J.E. Thomas, Springer Science & Business Media, 2012, p. 204 and Plato: A Collection of Critical Essays, vol 1: Metaphysics & Epistemology, NA NA,Springer, 2016, p. 110 and Reformation and Scholasticism in Philosophy, Vol. I, Herman Dooyeweerd, Paideia Press, 2012, p. 171-173).

- The Platonic Allegory of the Cave -

Immediately afterward, at the beginning of Book VII of The Republic (380 BCE), the same doctrine is elaborated in the Allegory of the Cave. The Allegory of the Cave puts in simple terms what Plato envisioned education to mean. In the Allegory of the Cave, Plato portrays education as the process of leaving the cave into the sunlight and becoming a philosopher (King). Once the philosopher, as that is what he is now, has left the cave completely, he will see real objects in the sunlight; the Forms. The way towards the essence of the Forms or the truth behind apearence is based on the Socratic or dialectical method or the 'Ars definiendi': "The dialectic remains the only intellectual process whose method is that of dissecting hypotheses and ascending to first principles in order to obtain valid knowledge". Dialectic is the process by which thought leads one from ignorance to understanding-knowledge. Dialectic or the method of hypothesis brings man from 'hypothesis' to 'thesis'. The method of hypothesis works by means of putting forward hypotheses (statements whose truth we do no know) and then investigating the consequences of that hypothesis in order to determine its truth. Discussion is the spur to dialectic. Through talking with each other, people can delve more deeply into problems and figure out an answer. Dialectic is to be distinguished from dianoetic. In Book VII of The Republic Plato puts forward his educational or scientific program. As the dialectician works bottom-up through each level, he understands and experiences just how the copy (sense information) is generated, or derived from the model (Forms), and since he grasps the essence of each he can give an account of the structural similarity between these aspects of mind functioning and explain how it is related to reality. The philosopher-dialectican moves through the lower levels of mere imagery towards the 'Forms' and the 'Good'. The dialectical method develops rationality in the realm of intellection, or understanding-knowledge, by education, practices, and training. Understanding-knowledge however is being destroyed in the realm of opinion, or picture thinking-belief, by those imitators at the lower levels, who only copy appearance without concern for the truth or reality (Forms) behind what they copy (appearence). In his Parmenides, Plato applies his method of deduction in order to prove his point with regard to the Forms.

Platonism therefore was a basic understanding of the operation of the cosmos, which saw the material world in a dualistic fashion; separated from the transcended Ideas or Forms, but communicated with by the logos (thought, wisdom, creativity). Platonism thought of the spiritual world of the Forms as perfect and stable and the physical world as imperfect and ever changing. The Platonic tradition assumed that the mind, once prodded by the senses, roams around in search of ideas, namely the truth beyond the object and the thought. The abstract reign of ideas has to be the foundation of both reality and thought-of-reality. Therefore the Platonic Forms are the truth. Ideas in Platonism are not - as frequently misunderstood - lofty templates of the real things; rather, ideas are the very structure and power of the mind to actively search and create concepts. Platonic ideas like Truth and Goodness (the One as the Basic Form from which emanate al other Forms) are ingrained in human minds as the means to judge about particulars. The human mind is the essence of man (e.g. anima rationalis est forma corporis); and due to the common mobility of everything living it is also the driving force of human life. Whatever man can know about the life of the body is known through the mind, and whatever the body does it does it in the service of human life. For human life, too, is motion. The human mind/soul is the link that connects all parts of the cosmos; therefore cosmology and epistemology (study of knowledge, science, logos) converge in human reason.

Plato maintains a traditional Greek virtue-based eudaemonistic conception of ethics. Human well-being (eudaimonia) is the highest aim of moral thought and conduct, and the virtues (aretê: 'excellence') are the requisite skills and dispositions needed to attain it. On morality Plato in his dialogue Euthyphro would put forward the Euthyphro dilemma: "Is the pious (τὸ ὅσιον) loved by the gods because it is pious, or is it pious because it is loved by the gods?" (Euthyphro, 10a). The dilemma illustrates Socrates's problem with the traditional stories about the gods and in the Euthyphro Socrates separates morality from the gods. It is closely related to the developmentof the concept of the Forms and the immortality of the soul
(see also The Big Argument: Does God Exist?, John Ashton, Michael Westacott, New Leaf Publishing Group, 2006, p. 175).

In the Protrepticus, which was reconstructed, Aristotle (384-322 BCE) gives his view on philosophy. For Aristotle everyone should practice philosophy, because even arguing against the practice of philosophy is itself a form of philosophizing. Aristotle's Protrepticus was one of the sources of which Iamblichus (ca. 245-ca. 325 CE) made extensive use in his writing with the same title
(see also Basic Concepts of Aristotelian Philosophy, M. Heidegger, Indiana University Press, 2009 and The Philosophy of Aristotle, Aristotle, Penguin Group (USA) Incorporated, 2011 and Aristotle and His Philosophy, A. Edel, Transaction Publishers, 1995).

Aristotle differed from Pato in his epistemology or the foundation of knowledge. In his epistemology Aristotle tried to give a new answer to the question of how true knowledge and its development is possible. However like Plato (Ideas) he attempts to build-up his epistemology from a sufficient ground outside knowledge (Forms). Aristotle regarded Metaphysics as the first philosophy and Physics as dependent on Metaphysical principles, and therefore Physics is to be considered a second philosophy. For Aristotle physics (or natural science) is concerned with things which are 'movable' or 'changeable', while metaphysics is concerned with things which are 'immovable' or 'unchangeable'. The interaction between these two "philosophies" is not completely exhausted by the causal influence exerted on the world by the supra-physical entities-the prime movers as it turns out. Aristotle's metaphysics and physics use a common conceptual framework, and they often address similar issues. The prime and distinctive task of first philosophy is an inquiry into first entities; these, however, are not perceptible entities, and as a result they have to be investigated through a metaphysical investigation of physical entities. Hence the overlap between the two disciplines, which often verges on inseparability. In his philosophy Aristotle considered the life of man as a potentiality striving towards its fulfillment. "Potentiality" (dunamis) and "Actuality" (energeia, entelecheia) are principles of a dichotomy which Aristotle used throughout his philosophical works to analyze motion, causality, ethics, and physiology in his Physics (350 BCE), Metaphysics (350 BCE), Nicomachean Ethics (350 BCE) and De Anima (350 BCE) (E: On the Soul). Aristotle tried to solve the problem of how something can become something else (e.g.. Parmenides) by differentiating between the potentiality and actuality present in a substratum or matter. Motion (kinêsis) is seen as "the fulfillment of what exists potentially, insofar as it exists potentially". The concept of potentiality, in this context, generally refers to any "possibility" that a thing can be said to have. Actuality, in contrast to potentiality, is the motion, change or activity that represents an exercise or fulfillment of a possibility, when a possibility becomes real in the fullest sense. Life is a dynamic principle for Aristotle and it contains its essence within itself (immanent), instead of a transcendent ideal Form for Plato. The ideal or essence of anything is present within (its) Nature (Gr. physis) instead of only in a supranatural ideal world (Plato) and it can be known by man through the study of Nature itself. Man therefore can find the truth also within himself, but as the system of body (Matter of a person, Being) and soul (Form of a person, the structure and characteristics, Essence) is different for every human being, the truth once found by an individual cannot be shared with others. The combination of Being and Essence and Potentiality (dunamis) and Actuality (Energeia and Entelechia) for every individual being is unique and intertwined and therefore cannot be shared between individuals (hylomorphism)
(see also Aristotle's Metaphysics: Form, Matter and Identity, J. Kirby, Continuum, 2008 and Routledge Philosophy GuideBook to Aristotle and the Metaphysics, V. Politis, Routledge, 2004).

Aristotle held that there were three basic activities of man: theoria, poiesis and praxis. There corresponded to these kinds of activity three types of knowledge: theoretical, to which the end goal was truth (Nicomachean Ethics, book X); poietical, to which the end goal was production; and practical, to which the end goal was action. Theoria, the noblest form of human activity, is the contemplation of that which is eternal and unchanging. Praxis, by contrast, refers to human action or activity in the realm of the contingent, that which could be other than it is and which we seek to affect by our actions. Poiesis refers specifically to production, the purposeful bringing-into-being of something distinct from its human producer (Poetics). Aristotle differentiated between praxis, denoting self-referential conduct, and poiesis, denoting a function-oriented, productive action. He distinguished both based on their teleological meaning, where poiesis is necessary, function-related actions, within which one can subsume work, and the paradigm of freely chosen, meaningful activities (praxis). Aristotle regarded poiesis as an inferior form of activity, subservient to an external end, that of the product's consumer rather than its producer. Praxis, on the other hand, designates virtuous political and ethical action that contributes directly to the actor's own happiness (eudaimonia), rather than serving ends determined by others.

In the 3^rd Century BCE Aristotle's Metaphysics (meaning beyond physics) was the first major work of the branch of philosophy with the same name. Scholars at Alexandria in the first century CE, brough together these works of Aristotle which were being referred to as 'τα μετα τα φψσικα' (E: after or beyond the Physics). In the manuscripts, the books are referred to by Greek letters. Book 1 of the Metaphysics is called Alpha (Α); 2, little alpha (α); 3, Beta (Β); 4, Gamma (Γ); 5, Delta (Δ); 6, Epsilon (Ε); 7, Zeta (Ζ); 8, Eta (Η); 9, Theta (Θ); 10, Iota (Ι); 11, Kappa (Κ); 12, Lambda (Λ); 13, Mu (Μ); 14, Nu (Ν). The books are sometimes brought together into three groups: Books I-VI: Alpha to Epsilon, The Middle Books (VII-IX: Zeta, Eta, Theta) and Books X-XIV: Iota, Kappa, Lambda, Mu and Nu.

The principal subjects of the Metaphysics are the 'study as such' of 'being' (subject matter) and 'qua being' (manner in which the subject matter is studied), or "being understood as being" (this is the Medieval interpretation and synthesis of the separate "being" and "qua being"). It examines what can be asserted about anything that exists just because of its existence and not because of any special qualities it has. Also covered are different kinds of causation, form and matter, the existence of mathematical objects, and a prime-mover, the unmoved mover or "Primum movens". In Metaphysics Α.1, it is stated that "all men suppose what is called wisdom (sophia) to deal with the first causes (aitia) and the principles (archai) of things", and it is these causes and principles which is dealt with in the Metaphysics. In Metaphysics Γ, Aristotle stated that first philosophy, the most general of the sciences, must also address the most fundamental principles, the common axioms, that are used in all reasoning. Thus, first philosophy must also concern itself with the principle of non-contradiction: the principle that "the same attribute cannot at the same time belong and not belong to the same subject and in the same respect". In Metaphysics Ζ, Aristotle takes up the study of substance (ousia): Matter (Being) and Form (το τι εν ειναι, Essence, the structure and characteristics) and the compound of matter and form (hylomorphism). Matter and Form compose substance synchronically, while potentiality (dunamis) and actuality (entelecheia or energeia) compose substance diachronically, across time. Aristotle deals with potentiality and actuality in Metaphysics Η.

In Metaphysics Λ Aristotle deals with the first causes and motion. At the opening of Metaphysics Λ, Aristotle characterizes the object of his inquiry as "the principles and causes of substances". He proceeds to a main division of substances into those that are changeable and perceptible, and those that are changeless and non-perceptible. He subdivides the changeable kind into changeable, perceptible, substances that are eternal (heavenly bodies), and ones that are perishable (sublunar). Aristotle put forward the concept that the material universe admits of two kinds of matter: terrestrial, which undergoes substantial as well as quantitative, qualitative, and local change; and celestial, which undergoes only change of place, local motion-and only perfectly circular local motion at that level. Sensible and perishable substances are those with which human beings are most familiar, being everything in the world, such as plants and animals. There are some sensible and eternal substances, however; these are the heavenly bodies, which move, but do so eternally. All sensible substances are the subject matter of physics, which is the science that studies substances as moving. The study of the immovable type of substance belongs to another science (theology). Aristotle noted that things in nature are caused and that these causes in nature exist in a chain, stretching backward. The central question about such causal chains, raised by Aristotle and others, is whether they must have a starting point. Aristotle, and others following him, claim that the answer is yes, i.e., that there must be a 'First Cause' because such causal chains cannot be infinite in length. To Aristotle the first cause has no potentiality but only actuality and therefore is pure energy or energeia (in Greek) or actus (in Latin): energy causes motion. Aristotle's concept of the 'Unmoved Mover' or 'Self-Thinking Thought' has no body, no materiality, no potentiality. For Aristotle all natural motions are uncaused and therefore self-explanatory (motion is an attribute of substance and no external force which acts upon a body, motion for Aristotle is not a secondary property derived from spatial and temporal change). For Aristotle, the 'First Cause' as a necessary being has always existed from eternity and there is only one such First Cause (this is a monotheistic interpretation of Aristotle as multiple 'First Causes' for a variety of chains of causation is also possible). All things may have the same first cause, or may have the same things as their first causes
(see also Aristotle and His World View, F. C. Brentano, University of California Press, 1978, p. 61).

For Aristotle nothing can come from nothing, but has to embedded in a certain context and a chain of causation. According to Aristotle and to the Greek philosophical tradition that went before him, it was impossible that there could be a 'creation ex nihilo', or out of nothing. "Therefore, as the saying goes, it is impossible that anything should be produced if there were nothing existing before. Obviously then some part of the result will pre-exist of necessity; for the matter is a part; for this is present in the process and it is this that becomes something" and "Therefore, as we say, generation would be impossible if nothing were already existent. It is clear, then, that some part must necessarily pre-exist; because the matter is a part, since it is matter which pre-exists in the product and becomes something". (Metaphysics VII, 7). For Aristotle no single thing is ever made out of nothing (ex nihilo), for the very reason that matter (hyle) is a part of everything that is produced or has a beginning, hence the part cannot be done away with so that there ever is nothing pure and simple. Aristotle definitely rejects any possibility of 'creation ex nihilo', for the simple reason that matter is made up of everything that is generated and with a beginning in time (reading the original Greek text makes this clear because the Arabic and Latin translations changed the original meaning of words like γενεστηαι, ηυπαρχει , ενυπαρξηει, γιγνεται). Aristotle in this follows the tradition of the Milesian philosophers who started with an analysis of matter (hyle) as the stuff things are made up of (and matter as the evident cause of everything that comes to be and passes away has no beginning). From this physical starting point of hyle as part of everything that is generated (see Physics, on Generation and Corruption, Metaphysics VII, 7), Aristotle goes on to figure out beyond the preceding philosophers the four causes that lead to wisdom (Physics II,3 and Metaphysics V, 2). The four causes are four types of things that can be given in answer to a why-question and all the four (types of) causes may enter in the explanation of something:

• The material cause: "that out of which", e.g., the bronze of a statue.
• The formal cause: "the form", "the account of what-it-is-to-be", e.g., the shape of a statue.
• The efficient cause: "the primary source of the change or rest", e.g., the artisan, the art of bronze-casting the statue, the man who gives advice, the father of the child.
• The final cause: "the end, that for the sake of which a thing is done", e.g., health is the end of walking, losing weight, purging, drugs, and surgical tools.

In philosophy and theology a doctrine of reality begins with a single "first principle", which is wholly certain, and it then proceeds to other propositions in the system through rigorous transcendental argument that communicates this certainty to them. For Aristotle the "Primum movens" (οὐ κινούμενον κινεῖ) was the first principle (origin) as opposed to the "Form of the Good" (ἡ τοῦ ἀγαθοῦ ἰδέα) of Plato. Aristotle refers to first principles in the opening passage of his Physics
(see also Aristotle's First Principles, T. Irwin, Oxford University Press, 1990). This kind of philosophy based on postulating qualitative first principles (conjectures) would hold until René Descartes (1596-1650 CE), but would finally be replaced by quantitative reasoning with the work of Isaac Newton (1642-1727 CE)
(see also Newton's Scientific and Philosophical Legacy, Paul B. Scheurer, G. Debrock (Eds.), International Archives of the History of Ideas Archives internationales d'histoire des idées, Vol. 123, 1988). Qualitative reasoning alone cannot lead to quantitative results or conclusions. Aristotle in his Metaphysics put forward a definition of truth: "To say of what is that it is not, or of what is not that it is, is false, while to say of what is that it is, and of what is not that it is not, is true". In the Categories (350 BCE) and De Interpretatione (350 BCE) Aristotle would provide the basis for the Correspondence Theory of Truth, which is the view that truth is correspondence to a fact.

Aristotle in his Physics deals with the most general (philosophical) principles of natural or moving things, both living and non-living. The Physics is composed of eight books, which are further divided into chapters. Aristotle stated that Nature (Gr. physis) is an inner principle of change and being at rest. This means that when an entity moves or is at rest according to its nature the reference to its nature may serve as an explanation of the event. The nature of the entity is in and of itself sufficient to induce and to explain the process once the relevant circumstances do not preempt it. Natures as inner principles of change and rest are contrasted with active powers or potentialities (dunameis), which are external principles of change and being at rest, operative on the corresponding internal passive capacities or potentialities (dunameis). When a change, or a state of rest, is not natural, both the active and the passive potentiality need to be specified. Natures, then, in a way do double duty: once a nature is operative, neither a further active, nor a further passive capacity needs to be invoked. Motion or change (kinêsis) is mentioned in the definition of nature, any discussion of nature will need to rely upon the explanation of motion. Because natures-beside the active and passive potentialities-are ultimate grounds in causal explanations, Aristotle sets out how they are integrated with the doctrine of causation and the concept of the four causes. By applying these principles of causality and through the application of logic such as by application of syllogisms, (Organon) man can find truth (beauty) as opposed to the deductive and mathematical approach of the Pythagorean and Platonic tradition
(see also Aristotle's Physics: A Guided Study, J. Sachs, Rutgers University Press, 1995).

For Aristotle, episteme or true knowledge, as opposed to doxa (opinion), is the result of logical reasoning through syllogism as opposed to the "Forms" of Plato. Episteme is "alethes doxa" (true opinion) supplemented by the right kind of syllogism. Aristotle substituted the explanatory and justificatory argument of Plato concerning knowledge with decompositional analysis. Both Plato an Aristotle are indebted to the Greek tradition of geometrical reasoning.

In Europe logic as a fully systematic discipline begins with Aristotle and Aristotelian logic would have a profound impact on the development of Western logic. The basic elements of Aristotelian logica are terms, propositions and syllogisms (υλλογισμός). Together they constitute the elements and instruments of thinking. The proposition connects the terms and the syllogism connects propositions. A proposition is ideally composed of at least three words: a subject (a word naming a substance), a predicate (a word naming a property), and a connecting verb (copula)
(see also Logic: An Aristotelian Approach, Mary M. Spangler, University Press of America, 1993, p. 73 and Aristotle on Truth, Paolo Crivelli, Cambridge University Press, 2004, p. 10).

In the six parts of the Organon (Ὄργανον) Aristotle put forward his ideas on logic. The Aristotelian Organon consisted of the Categoriae or Predicamenta, De interpretatione, (Greek: Peri Hermeneias), Analytica Priora, Analytica Posteriora, Topica, and De sophisticis elenchis. The Aristotelian Organon is traditionally divided into three main parts. The first part of the Organon deals with the understanding of elementary concepts or 'simplex apprehensio' (Categoriae), the second part with sentences and evaluation or 'judiciaire' (De interpretatione) and the third part with argumentation (Analytica Priora, Analytica Posteriora, Topica and De sophisticis elenchis).

The basic terms of Aristotelian logic are general concepts (essentials). Contrary to Plato these are nog transcendent Forms but are extracted by the active intellect (nous poiêtikos or intellectus agens) from what is being perceived by the passive intellect (nous pathetikos or intellectus possibilis). The active intellect extracts the general essence (eidos, universal) out of the particular. The 'universale post rem' comes from understanding the 'universale in re'. We have the universal as found in the thing in the world (universale in re); and the universal following upon the thing in the world (universale post rem). The extracted essences or universals are the most fundamental properties. In the Categoriae Aristotle puts forward his theory of categorialism, which states that the fundamental properties are categorical. Aristole distinguishes between the to ti ên einai (essence, substance) and the accident of an entity. The essence is the attribute or set of attributes that make an entity or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity. Essence is contrasted with accident: a property that the entity or substance has contingently, without which the substance can still retain its identity. The nine kinds of accidents according to Aristotle are quantity, quality, relation, habitus, time, location, situation (or position), action, and passion ("being acted on"). Together with "substance", these nine kinds of accidents constitute the ten fundamental categories of Aristotle's ontology
(see also The organon, or, Logical treatises of Aristotle, Aristotle, Prometheus Trust, 2001 and Substance and Essence in Aristotle: An Interpretation of Metaphysics VII-IX, C. Witt, Cornell University Press, 1994).

- Arbor Porphyriana from the Isagoge of Porphyry of Tyre -

Besides the categories Aristotle also distinguishes between the different relations or praedicabilia (κατηγορόυμενα or modes of predicating) between universal concepts. The definition of something is the statement of its essence and the Aristotelian classification is the predication of one universal concerning another. Aristotle then defines a fivefold classification system on universals:

• definition (horos) which is the statement of its essence (τὸ τί ᾖν εἶναι),
• genus (γένος, genos),
• differentia specifica (διαφορά, diaphora),
• property (ἴδιον, idion, proprium),
• accident (συμβεβηκός, sumbebekos, accidens)

The most fundamental category in the Aristotelian system is substance and Aristotle divides substance into primary and secondary substances. The highest categories are in themselves indefinable. In his classification system (praedicabilia) the essence of a species (definition/species), its genus, is differentiated into a species by some set of differentiae. Genus is that part of the essence which is also predicable of other things different from them in kind. Differentia is that part of the essence which distinguishes one species from another. A property is an attribute which is common to all the members of a class, but is not part of its essence. An accident is an attribute which may or may not belong to a subject. The essence of any species then consists in its genus (generic concepts) and the differentia that together with that genus defines the species (specific concept or kind)
(see also Logical Thinking in the Pyramidal Schema of Concepts: The Logical and Mathematical Elements, Lutz Geldsetzer and Richard L. Schwartz, Springer, 2013, p. xiii). The system starts with the supreme genus and down to the most specific species
(see also the Isagoge with the Arbor Porphyriana of Porphyry (ca. 234-305 CE) and The Development of Logic, William Kneale and Martha Kneale, 1968, p.232). Aristotle diferentiated between essence, which is essential to define something and accidents, which can change without touching the essence.

Properties depend on instantiations of other properties (as opposed to hylomorphism which Aristotle would develop later). The Predicamenta consist of three parts: the Pre-Predicamenta (chs.1-4), the Predicamenta (chs. 5-9), and the Post-Predicamenta (chs. 10-15). In the Pre-Predicamenta, Aristotle discusses a number of semantic relations, gives a division of beings, into four kinds, and then presents his canonical list of ten categories. In the Predicamenta, Aristotle discusses in detail the categories of substance, quantity, relatives, and quality, and provides a cursory treatment of the other categories. And finally, in the Post-Predicamenta, he discusses a number of concepts relating to modes of opposition, priority and simultaneity, motion, and ends with a brief discussion of having. In the Pre-Predicamenta Aristotle gives a classification of being, based on the structure of Indo-European languages, which use a subject and its predicate connected together with a copula. Every Indo-European sentence contains two parts: a subject and a predicate. The subject is what (or whom) the sentence is about, while the predicate tells something about the subject. The subjects become the universals (ουσια, essence or substance) of Aristotle's philosophy and the predicates become the categories. The copula can either connect two universals of which one becomes a predicate (secondary substances) by means of "is" (identity) or connect a universal to a category with "has" (property). Primary substances never become predicates, while secondary substances can be a substance and a predicate in "is" (identity) relation to the substance. In the Predicamenta Aristotle puts forward his tenfold classification into categories of that which exists. These Aristotelian categories consist of substance, quantity, quality, relation, place, time, situation, condition, action, and passion. In the Aristotelian system, quantity (mathematics) does not play the same important role which number has in the Pythagorean system or which it would get during the Scientific Revolution. Quantity however is a special category in a realist view on universals as it is the category which leads to individuation of the universal (principium individuationis) in its factual existence (particular). In the Post-Predicamenta four ways are given in which things may be considered contrary to one another. Next, the work discusses five senses wherein a thing may be considered prior to another, followed by a short section on simultaneity. Six forms of movement are then defined: generation, destruction, increase, diminution, alteration, and change of place. The Categoriae ends with a brief consideration of the word 'have' and its usage.

With Aristotle starts the development of the 'logica artificialis' as distinguished from the 'logica naturalis'. His study of logic provided the earliest formal study of logic in the Western tradition and as such of inferential systems.
(see also Models of the History of Philosophy, Volume 2, Giovanni Santinello, Springer, 1979, p. 379). In De interpretatione he introduces his conception of proposition and judgment, and the various relations between affirmative, negative, universal, and particular propositions. De interpretatione contains Aristotle's principal contribution to philosophy of language. It also discusses the 'Problem of future contingents', which are statements about states of affairs in the future that are neither necessarily true nor necessarily false. In the Analytica Priora Aristotle introduces his syllogistic method, argues for its correctness, and discusses inductive inference. Aristotle in his logic uses categorical syllogisms, which consist of three categorical propositions: a major premise, minor premise and conclusion. The Analytica Posteriora deals with demonstration, definition, and scientific knowledge. In the Topica Aristotle treats issues in constructing valid arguments, and inference that is probable (dubitabile), rather than certain. Here he discusses which subjects can be an element of debate (disputatio) beacause they are 'dubitabile'. This excludes those element which are part of 'common sense' and those which are not to be doubted (e.g. dogmata, matters of faith). Therefore only a subset of possible topics is amenable for debate. In the De sophisticis elenchis he deals with logical fallacies
(see also Aristotelian Logic, W. T. Parry, E. A. Hacker, SUNY Press, 1991 and Aristotle and Logical Theory, J. Lear, CUP Archive, 1986).

Aristotle developed a demonstrative logic, the demonstration of derivations from known principles. In his logic there are two logical qualities: affirmation (kataphasis) and denial (apophasis). The logical quality of a proposition is whether it is affirmative (the predicate is affirmed of the subject) or negative (the predicate is denied of the subject). His logic therefore is bimodal as it only allows statements to be either true or false (a trimodal logic is also used, which contains operators for knowledge and time)
(see also De Interpretatione, section 6, Aristotle and Greek, Indian and Arabic Logic, Dov M. Gabbay, John Woods, Elsevier, 2004, p.148).

In his logic Aristotle put forward three laws of thought, which are the fundamental axiomatic rules upon which any rational discourse is to be based:

• Law of identity: a thing is what it is
• Law of noncontradiction: no thing can be what it is not
• Law of the excluded middle or excluded third (tertium non datur): of two contradictory propositions one must be true, and the other false

Aristotle developed a method for constructing logical arguments, the syllogisms
(see also Aristotle's Theory of the Syllogism, G. Patzig, Springer, 1968 and A Companion to Aristotle, G. Anagnostopoulos, John Wiley !; Sons, 2013, Ch. 3, Deductive logic). A syllogisms is a kind of logical argument in which one proposition (the conclusion) is inferred from two or more others (the premises) of a certain form. Syllogisms are particularly interesting in persuasion as they include assumptions that many people accept which allow false statements or (often unspoken) conclusions to appear to be true. There is a difference between truth and validity in syllogisms. A syllogism can be true, but not valid (i.e. make logical sense). It can also be valid but not true. The syllogism itself consists of three parts (statements or premises) and three terms, the terms of which are used twice. Each statement has a subject (what the statement is about) and a predicate (what is being said about the subject). The subject of the conclusion is the minor term and the predicate of the conclusion is the major term. The term that appears in the premises, but not in the conclusion is the middle term. The premise with the major term is the major premise and the premise with the minor term is the minor premise:

• The major premise, a general statement: "Socrates is a man", which simply states that Socrates belongs to a category of object which we call "man". Such categories like "man" are the universals.
• The minor premise, a specific statement: "all men are mortal". All categories are defined by their characteristics, some of which are essential and some of which are accidental. This minor premise simply specifies one of the essential characteristics of the category "man". The middle term of a syllogism is also a Socratic definition. Both the major and minor premise must share a middle term which connects them.
• The conclusion, based on the two premises: "Socrates is mortal". The major premise is based upon the observation that "Socrates" displays the necessary essential characteristics to place him in the category of "man". If so, then Socrates has all of the essential characteristics of the category.

• Categorical Syllogism: If A is in C then B is in C. Both premises are known to be valid, by observation or historical facts. Because the two premises are valid, the conclusion must be valid as well. Be aware that this conclusion is based on logical reasoning and thus it doesn't have to represent the "truth" always.
• Conditional Syllogism: If A is true then B is true (If A then B). Conditional syllogisms are better known as hypothetical syllogisms, because the arguments used here are not always valid.
• Disjunctive Syllogism: If A is true, then B is false (A or B). These syllogism types do not actually state that a certain premise (major or minor) is correct, but is does states that one of the premises is correct.

• Categorical Propositions: Statements about categories.
• Enthymeme: a syllogism with an incomplete argument.
• Modus Ponens or hypothetical syllogism: If X is true then Y is true. X is true. Therefore Y is true.
• Modus Tollens or disjunctive syllogism: If X is true then Y is true. Y is false. Therefore X is false.

• A-Universal Affirmative: This is a syllogism of the form: All X are Y.
• E-Universal Negative: This is the negative form of universal affirmative, which is a syllogism of the form: No X is Y, or as example: No humans are perfect. This syllogism type is exactly the opposite of proposition "A" explained above.
• I-Particular Affirmative: Another syllogism type is the "particular form" which only influences some people and not the whole population. This syllogism is of the form: Some X are Y.
• O-Particular Negative: The opposite of proposition "I" is proposition "O" which is of the form: Some X are not Y. an example of this would be: some swans are not white.

In the Posterior Analytics Aristotle stated that all teaching and learning result from previous cognition. We presuppose that something is (the fact, modus descendi); or we comprehend what it is (the reasoned fact, modus cogendi). In the Posterior Analytics Aristotle also stated that no science proves its own matter or posit (thesis). The posit (thesis) is something that cannot be proved, but needs not be grasped by anyone who is to learn. An axiom (axiom) is also something that cannot be proved, but must be grasped by anyone who is to learn. Logic as a science is both a part and an instrument of philosophy and logic proves every posit. Therefore the posit cannot be its matter. That no art proves its own matter is proved in this way: every art has its principles that it does not prove, but by which it proves the other things in the art. If it proved its principles, then those by which it proved them would be better known, and so the principles of the art would not any longer be principles. Hence in every art certain principles are assumed, which are granted, and afterwards, in another art, are proved, and so no art proves its own principles. But its matter is one of its principles, so that no art proves its own matter.

Aristotle realized, there must be propositions that do not need, for whatever reason, to be proven. Such propositions he called the first principles (archai, principia) of demonstration. Any transcendental deduction establishes the right (quid juris) by which we are entitled to use pure concepts a priori for the possibility of experience. This was later put forward by Immanuel Kant (1724-1804 CE) in the Transzendentale Logik of his Kritik der reinen Vernunft and criticised in the Versuch über die Transcendentalphilosophie of Solomon Maimon (1753-1800 CE). The first principles of any philosophical system cannot be proven or validated by the system itself, but are mere axioms or dogmas which are being 'bootstrapped'. This classical solution for establishing first principles leads to logical difficulties, because postulating first principles either leads to an infinite regress, or a logical circle or a dogmatic roadblock on the attempt of justification (quid facti)
(see also Dictionary of Untranslatables: A Philosophical Lexicon, Barbara Cassin, Emily Apter, Jacques Lezra, Michael Wood, Princeton University Press, 2014, p. 582 and Symbolic Forms as the Metaphysical Groundwork of the Organon of the Cultural Sciences: Volume 2, Israel Bar-Yehuda Idalovichi, Cambridge Scholars Publishing, 2014, 546).

Aristotle in his Poetics distinguishes reality from its representation, and he discusses representation in three ways:

• The object: The symbol being represented.
• Manner: The way the symbol is represented.
• Means: The material that is used to represent it.

In De Anima (350 BCE) (E: On the Soul) Aristotle discusses the soul and the intellect. In De Anima (350 BCE) (E: On the Soul) and the Parva Naturalia, Aristotle postulated the union of body and soul by saying that the soul is the form of the body. In these works he puts forward his ideas on human psychology. For Aristotle the intellect was an aspect of the soul and the soul is the form of the body, not a separate substance. Therefore the body (Matter of a person, Being) and soul (Form of a person, the structure and characteristics, Essence, ουσια) are not two separate elements but one thing. The soul for Aristotle is not immortal, it does not separate from the body because it is what makes the body a person rather than just matter (it is the form of a person). All the faculties of the soul are inseparable from the body with the exception of reason. It has been suggested that Aristotle believed that reason is immortal, although this remains unclear. However, if reason does have the capacity to facilitate some sort of life after death it cannot not have a personal, recognisable identity. In characterizing the soul and body in these ways, Aristotle applies concepts from his hylomorphism, meaning both matter (hulê) and form or shape (morphê). Aristotle with this concept introduces the soul as the form of the body, which in turn is said to be the matter of the soul, Aristotle treats soul-body relations as a special case of a more general relationship which obtains between the components of all generated compounds, natural or artifactual. In Aristotelian hylomorphism, bodies are characterized as an inseparable combination of matter and form, and in his physics all bodies were held to consist of a particular combination of the four elements: fire, air, water, earth. The Aristotelian compounds are entities on themselves as opposed to the atomism (minima naturalia) of Democritus (ca. 460-370 BCE) for whom conglomerates are only mere collections of atoms with no independent supra-atomic existence or meaning of their own
(see also The Powers of Aristotle's Soul, T. K. Johansen, Oxford University Press, 2012 and Aristotle's De Anima: A Critical Commentary, R. Polansky, Cambridge University Press, 2007 and Aristotle de Anima: Ensouled Body, F. Rhodes, D. W. Hamlyn, P. Herel, J. Zimmer, CUP Archive, 1993).

In De Anima (350 BCE) (E: On the Soul) (Bk. III, ch. 5, 430a10-25) and the Metaphysics (350 BCE) (Book XII, ch.7-10), Aristotle discusses the intellect, such as the passive intellect (nous pathetikos, intellectus possibilis) which receives the mental images (phantasmata) of the universals through the senses (e.g. 'Nihil est in intellectu quod non prius in sensu') and the active intellect (intellectus agens) which illuminates the phantasmata, and divests them of all individuating conditions (particularia). In the peripatetic tradition and the commentaries on Aristotle, the relation between both intellects and the location of the active intellect (one shared intellect or individual) would vary.

Aristotle would have a major influence on Medieval Byzantine (Greek) and Islamic philosophy, and Western (Christian) philosophy (Latin) with the development of Scholasticism. Thomas Aquinas (1225-1274 CE) would create a synthesis of Aristotelianism with Christianity into what became known as Thomism
(see also Thomism: An Introduction, P. B. Grenet, Harper & Row, 1967 and Thomism: The Philosophy of Thomas Aquinas, É. Gilson, Pontifical Institute of Mediaeval Studies, 2002 and Praeambula Fidei: Thomism and the God of the Philosophers, R. McInerny, Catholic University of America Press, 2006 and A Short History of Thomism, R. Cessario, Catholic University of America Press, 2005 and Catholicism and Science, P. M.J Hess, P. L. Allen, ABC-CLIO, 2008, p. 96).

Universals

Introduction

- The Platonic Allegory of the Cave -

The Problem of Universals is an ancient problem in metaphysics about whether universals exist as such. Universals are general or abstract qualities, characteristics, properties, kinds or relations. The problem of universals is about their status; as to whether universals exist independently of the individuals of whom they can be predicated or if they are merely convenient ways of talking about and finding similarity among particular things that are radically different. The realist school claims that universals are real - they exist and are distinct from the particulars that instantiate them. Nominalists assert that only individuals or particulars exist and deny that universals are real (i.e. that they exist as entities or beings). For nominalists, universals are merely words (flatus voci). The meaning of logic is also dependent on the position one takes on universals (mental signs). When one accepts an isomorphism between thought and reality, then logic as such is tautological. When one views universals as separate entities in the mind, then mind-logic is different from the logic of reality. The relation of universals to particulars (individuation) is also solved differently from a realist and nominalist viewpoint (Nominalism and Realism: Volume 1, D. M. Armstrong, CUP Archive, 1980 and A Theory of Universals: Volume 2, D. M. Armstrong, CUP Archive, 1980 and Fundamentals of Western Philosophy, M. J. Ziccardi, 2010, p. 14).

The different positions about universals (Plato's ideas) are that universals exist 'ante res' (Plato), 'in res' (Aristotle), or 'post res' (Nominalists). Universalia 'ante res', means universal concepts come first. This is the view of Plato: Concept realism, concepts are not invented, rather they exist before reality and real things are copies of the concepts. Concepts are real (in this sense) and are discovered by the mind. Universalia 'in res' means universal concepts reside in real "things" ("res"). This is the view of Aristotle: Concepts exist in reality and are extracted by the mind, not invented, but discovered. They are sort of built into things. Knowledge is empirical and abstracted. Universalia 'post res' means universal concepts come after real "things". There are no concepts where there are no minds. Concepts are invented by the mind based on empirical studies, but they don't exist in physical reality itself. Nominalism means that there are no concepts, only the things themselves. Concepts are just names.

Universals in antiquity were part of the ordering principles of reality. The Pre-Socratics were preoccupied with matter, particles, etc., and they overlooked the concept of universals. Plato disscussed universals in his Republic and in the Timaeus. In classical philosophy, there were three ordering principles: "arche", which is the source of all things (universals as first principle of the world), "logos" (Gr. λογοσ), which is the underlying order that is hidden beneath appearances, "harmonia" which is exemplified by numerical ratios in mathematics. In Ancient Greek philosophy, "first principles" or universals are arkhai and the faculty used to perceive them is sometimes referred to in Aristotle (384-322 BCE) and Plato (424/423-348/347 BCE) as nous which was close in meaning to "awareness" and therefore "consciousness". Logos has multivocal meanings in ancient Greek: word, reason, rational order, etc. If logos is meant as reason, the incarnate logos expresses the rational structure of human existence based on the principle of light. If logos is regarded as the word, the incarnate logos is the symbolic system that constitutes spirit. Hence, incarnate logos is the structural word of life combining both of the above meanings. Harmonia is the interaction or mean of two or more parts to create a whole which transcends the properties of its elements (e.g. Triadic Principle or Law of Mean Terms).

The ancient Problem of Universals would be continued in the Medieval Problem of Universals during the European Middle Ages. The Neoplatonist Porphyry (ca. 234-305 CE) introduced the problem in his Isagoge as an introduction to Aristotle's Categories (350 BCE). Since "authority has a nose made of wax", it was possible for medieval interpreters to twist it in any direction, so that the classical Indo-European (logos meaning reason) philosophy could be fitted into the new Semitic (logos meaning word) framework. What line of argument a complex or ambiguous authority supports on universals depends on how one interprets that authority, and interpretation itself can go, at least much of the time, in more than one direction.

Platonic realism would take the most extreme position concerning universals, as he stated that they exist completely 'ante res'. Plato wants to provide an ontology of concepts by making them real. A general idea or concept, according to Plato, is immutable, timeless, one over many, intellectually apprehensible and capable of precise definition at the end of a piece of pure ratiocination (reasoning) because it is an independently existing real thing or entity. For Plato universals (eidos) exist as such and independently from physical reality and they are eternal. The eidos or form is that which makes a thing to be what it is. Plato will argue in the Phaedo, that there must be something in us that is akin to the forms or ideas or universal essences if we are able to know them, have them, contain them. Since for Plato the particular does not contain the universal, but vice versa, there must be an immaterial nature within us if we are able to contain universal ideas. This is the Platonic soul. The Demiurge (Craftsman) orders primordial matter with forms and numbers into existence, bringing the elements under rules out of chaos (see the comment on the Timaeus). Plato's universals (Forms) include numbers and geometrical figures, making them a theory of mathematical realism; they also include the Form of the Good, making them in addition a theory of ethical realism. With his solution on Universals Plato tried to solve the question wether reality is ultimately one (monism, monocausal) or ultimately many things (pluralism, pluricausal). Plato in his solution brought together both of these ideas. He believed that reality was in the form of two separate worlds, otherwise known as a two-tiered metaphysics. He believed that something was an individual object, but could be put together into a larger group from which the individual object was derived. There is the world of sense experience (the 'empirical' world), where nothing ever stays the same but is always in the process of change. Experience of it gives rise to opinions (doxa). There is also a world which is outside space and time, which is not perceived through the senses, and in which everything is permanent and perfect or Ideal, which is the realm of the Forms. The empirical world shows only shadows and poor copies of these Forms, and so is less real than the world of the Forms themselves, because the Forms are eternal and immutable (unchanging), the proper objects of knowledge. Plato believed that these Forms were interrelated, and arranged in a hierarchy. The highest Form is the Form of the Good, which is the ultimate principle. Real knowledge becomes, in the end, a knowledge of goodness
(see also A History of Western Thought: From Ancient Greece to the Twentieth Century, N. Gilje, G. Skirbekk, Routledge, 2013, p. 122).

In his dialogue Meno, Plato describes the discussion about the real nature of arete between Socrates (469-399 BCE) and Meno. Socrates wants to define arete at the general level of a universal or 'Eidos' (realist position), while Meno defines arete in particulars (nominalist position) and their positions cannot be reconciled. The dialogue first deals with the plurality of things and the unity of signs and then the dialogue deals with the plurality of signs (words as sings) and the unity of universals. The universal or 'Eidos' of arete for Socrates has to provide the underlying foundation which all particular (physical) instances of arete have in common. Without universals there are no common characteristics (shared essences) and there can be no identity, but only similarity. Meno and Socrates however do not reach a common ground and neither of them can say at the end of the dialogue what virtue is. The controversy between realism and nominalism begins.

Plato in book VII of the Republic uses the Allegory of the Cave to illustrate "our nature in its education and want of education". The Allegory is related to Plato's Theory of Forms on Universals, according to which the "Forms" (or "Ideas"), and not the material world of change known to us through sensation, possess the highest and most fundamental kind of reality. Only knowledge of the Forms constitutes real knowledge. Plato believed that the Forms were interrelated, and arranged in a hierarchy. The highest Form is the Form of the Good, which is the ultimate principle. In addition, the Allegory of the Cave is an attempt to explain the philosopher's place in society: to attempt to enlighten the "prisoners". Plato's position therefore is that in order to explain the qualitative identity of distinct individuals, we must accept that there is another entity besides the resembling individuals, which is the Universal or Platonic Form.
The myth of the cavern describes our situation regarding knowledge: we are like the prisoners of a cavern who only see the shades of the objects and so live in complete ignorance worrying about what is offered to our senses. Only philosophy can release us and allow us come out of the cavern to the true world or World of the Ideas. Plato argues a liberated prisoner would slowly discover different levels of authentic reality: first he would see the objects and the light inside the cavern, later he would come out of it and see first the shades of the objects, then the reflections of those objects on the water and finally the real objects. At last he would see the Sun and conclude it is the reason of the seasons, it rules the realm of visible objects and is the reason of everything the prisoners see. And remembering his life in the cavern, remembering what he thought he knew there and his captivity comrades he would feel happy for being free and would feel sorry them; prisoner's life would seem unbearable for him. But in spite of it and in spite of the dangers, his clumsiness and the prisoner's laughs and scorns, he would return to the underground world to free them.

A somewhat less extreme form of realism 'ante res' would postulate that only the general Idea of a Form existed within the 'first principle' from which it emanates, thereby taking into account the required unity of the 'first principle'. When the forms exist entirely within the 'first principle' this endangers its status as eternal and unchanging.

Aristotle would take the position concerning universals that they exist 'in res' as opposed to Plato. Aristotle in his Metaphysics would oppose the Platonic Theory of Forms and its negative vision of the material world and man's inability to derive truth from observing reality and by means of induction reach truth. In his Metaphysics Aristotle would develop its own theory of universals as a solution to the problem of universals in contrast to Plato's Theory of Forms. His Categories (350 BCE) would become the source from which the discussion on universals started in the Western tradition as opposed to the Eastern Platonic tradition. Aristotle first defines 'substantia' and 'accidentia' in which he distinguishes between things which are present within a subject and things which are predicable (said of) a subject (e.g. the categories). Universals are predicable of particulars in that particulars instantiate or exemplify universals ('in re'). In Aristotle's view, universals exist only where they are instantiated; they exist only in things (he said they exist 'in res', which means simply "in things"), never apart from things as with Plato. Beyond this Aristotle said that a universal is something identical in each of its instances. Aristotle proposed a logical method (syllogisms) to reach truth from observing reality, thereby providing an anternative for the Pythagorean and Platonic mathematical and deductive approach to knowledge. For Aristotle truth only exists when 'substantia' and 'accidentia' are placed in a sentence (syllogism, context). Before this happens truth as such is not yet present within the singular 'substantia' and 'accidentia'
(see also A History of Western Thought: From Ancient Greece to the Twentieth Century, N. Gilje, G. Skirbekk, Routledge, 2013, p. 122).

Leucippus (first half of 5th century BCE) and Democritus (ca. 460-370 BCE), the Laughing Philosopher (Abderitan laughter), formulated an atomic theory for the universe. They rejected the existence of universals 'ante res' and 'in res'. Complex entities were made out of particulars (atoms) and never became an entity in themselves. Universals had no existence in their own right, but were mere descriptions which came after the material instance which they described. This lead to pluralism with regard to causality. Causation is different in a realist and a nominalist (particulary materialist) viewpoint. Non-causal (accidental) and causal relations (and between mere regularities and the laws of nature, respectively) are viewed differently. The distinction between causation and mere succession is also different
(see also A History of Western Thought: From Ancient Greece to the Twentieth Century, N. Gilje, G. Skirbekk, Routledge, 2013, p. 123).

Body and Soul

Introduction

- The human soul and the Chariot of Plato -

quid est quod fuit ipsum quod futurum est quid est quod factum est ipsum quod fiendum est
nihil sub sole novum nec valet quisquam dicere ecce hoc recens est iam enim praecessit in saeculis quae fuerunt ante nos
- Vulgata, Ecclesiastes I: 9-10 -

The soul (psyche, anima) is defined as the incorporeal and, in many conceptions, immortal essence of a person, living thing, or object. The latin word 'anima' is the feminine form or 'soul', while 'animus' is the masculine form or 'mind'. The ancient Egyptians believed that man was composed of three parts: the body, spirit, and soul. The fate of the soul was determined by its actions during life, whether good or bad, and the amulets, prayers, and gifts offered to gain the favor of the gods. According to Herodotus (ca. 4840-425 BCE), the Egyptians believed that the soul was reborn as every sort of animal before returning to human form after 3,000 years. The Greek philosophical tradition of the immortality of the soul is believed to have started in southern Italy with Pythagoras (ca. 570-ca. 495 BCE), who was known as an expert on the fate of our soul after death. Pythagoras asumed the soul to be tetragonal or square, from which comes the importance of the tetrad or tetraktys and of the gnomon. He maintained that the soul of man consists of a tetrad, the four powers of the soul being mind, science, opinion, and sense. He believed that the study of mathematics could convert the soul from the world of the senses to the contemplation of the eternal
(see also The Fate of the Soul-Metempsychosis and Pythagoras and the Doctrine of Transmigration: Wandering Souls, 2009, James Luchte). The notion of the doctrine of metempsychosis (referring to transmigration of the soul) is accredited to Pherecydes of Syros (fl. 6^th century BCE), and thereby giving the first teaching of the immortality of the soul
(see also Body and Soul in Ancient Philosophy, 2009, Dorothea Frede, Burkhard Reis). For the atomist Titus Lucretius Carus (ca. 99-ca. 55 BCE) the human soul consisted of very fine atoms and was composed of two parts: the 'anima' which was distributed throughout the body, which is the cause of sensation, and the 'animus' which was located in the breast, the central consciousness. The Lucretian soul is born and grows with the body, and at death it is dissipated like "smoke". The Abrahamic religions would develop the concept of the immortality of the soul within the boundaries of their religion.

For Plato (424/423-348/347 BCE), the soul and the body are two different realities. Plato considered the soul the essence of a person, being that which decides how we behave. He considered this essence to be an incorporeal, eternal occupant of our being. The soul is divine by nature. The soul is eternal and immortal, but its association with the body is regarded as its fall from heaven. It has to be purified and if the purification is not sufficient, it has to undergo a cycle of reincarnations. As bodies die, the soul is continually reborn in subsequent bodies (Metempsychosis). The body is material, it is something inferior to the soul. Accordingly, the sensual or experimental cognition is inferior to the one based only on the speculative, intellectual exercise of the mind. Plato put forward his view on the afterlife and the cosmos in The Myth of Er which concludes Plato's Republic (X.614-10.621). The Myth of Er introduced the idea that moral people are rewarded and immoral people punished after death
(see also City and Soul in Plato's Republic, G. R. F. Ferrari, University of Chicago Press, 2005 and Phædo:Or, The Immortality of the Soul, Plato, J. Miller, 1854).

The Platonic soul comprises three parts: logos, or logistikon (wisdom, mind, nous, or reason), the thymos, or thumetikon (will, emotion, or spiritedness, or masculine), and the eros, or epithumetikon (appetitive, or desire, or feminine). The Three Parts of the human Soul are discussed in Plato's Republic and Phaedrus. The Soul of Appetite, the Soul of Will, and the Soul of Reason. Plato uses the analogy of a chariot to describe the three parts of the human soul. The Charioteer represents intellect, reason, or the part of the soul that must guide the soul to truth; one horse represents rational or moral impulse or the positive part of passionate nature (e.g., righteous indignation); while the other represents the soul's irrational passions, appetites, or concupiscent nature. The Charioteer directs the entire chariot/soul, trying to stop the horses from going different ways, and to proceed towards enlightenment. The appetites (temperance, Black horse on Left), includes all our myriad desires for various pleasures, comforts, physical satisfactions, and bodily ease. The "thymos" (courage, White horse on Right), spirited, or hot-blooded, part, i.e., the part that gets angry when it perceives (for example) an injustice being done. The "nous" (mind, wisdom), our conscious awareness, is represented by the charioteer who is guiding (or who at least should be guiding) the horses and chariot. This is the part of us that thinks, analyzes, looks ahead, rationally weighs options, and tries to gauge what is best and truest overall.
In Greek philosophy and medicine, the human body was filled with four basic substances, called four humors, which were in harmony when a person was healthy in mind and body. The four humors were black bile (melancholic), yellow bile (choleric), phlegm (phlegmatic), and blood (sanguine). This theory was closely related to the theory of the four elements: earth, fire, water and air. Black bile was related to earth, phlegm to water, blood to air, and yellow bile to fire.

The ideal, harmonious or healthy state of man was conceived simply as kairos, or due measure; in other authors this mean was numericized, and thus conceived as a proportion or ratio between two or more opposites (logos, summetria, harmonia, isonomia, etc., ...). Wherever the idea of a mean is found, it describes the state at which one should aim (the virtuous, health, beauty, etc., ...) which lies between an excess and a deficiency. The healthy state or mean wasn't the same as mediocrity. Being healthy in mind and body was (is) something very difficult to achieve. A healthy and harmonious state of mind and body was something to strive for, something fleeting and valued. However, the Melancholic, with a slightly off-center proportion of (hot) black bile was destined for eminence in philosophy or politics or poetry or the arts, ... .This goes for the melancholic 'mean' that is on the excessive side of the 'isonomic', healthy state, not the deficient. Melancholia, even though it is quite variable ('anomalian'), can be 'well-tempered' ('eukraton') and favourable ('kalos'), and thus all melancholics had 'remarkable gifts' ('perittos') (e.g. the engraving Melencolia I (1514) of Albrecht Dürer). The isonomic proportion was still the somatic ideal, but moderate melancholics were more likely to achieve this ideal than those who are naturally disposed to have their humours in equal balance when the environment was added into the equation. Melancholy resembles the aesthetic mode of facing the world, to see emotions and value in things, versus the reflective mode, which only analyzes and looks for causes and contexts.

Aurelius Augustinus or Augustine (354-430 CE) would write a treatise De immortalitate animae (387 CE) in the Neoplatonic tradition. The Renaissance scholar Marsilio Ficino (1433-1499 CE) wrote several works on Platonism, such as the Theologia Platonica de immortalitate animae on the immortality of the soul (Platonic theology)
(see also De Immortalitate Animae of Augustine:Text, Translation and Commentary, Saint Augustine, John Benjamins Publishing, 1977 and Saint Augustine and the Fall of the Soul, R. J. Rombs, Catholic University of America Press, 2006 and Marsilio Ficino: His Theology, His Philosophy, His Legacy, M. J. B. Allen, V. Rees, M. Davies, BRILL, 2000, p. 105 and The Science of Nature in the Seventeenth Century, J. A. Schuster, P. R. Anstey, Springer, 2006, p. 132).

Aristotle (384-322 BCE) defined the soul or 'psyche' as the first actuality of a naturally organized body, but argued against its having a separate existence from the physical body. In Aristotle's view, the primary activity of a living thing constitutes its soul; for example, the soul of an eye, if it were an independent organism, would be seeing (its purpose or final cause). Aristotle treats of the soul in his work De Anima (E: On the Soul). In De Anima the soul as an Aristotelian concept is in line with his philosophy of universal ontological principles of form and matter. Aristotle uses the term, the soul, but it has a different meaning than in previous accounts: The soul now being the form or actuality of the living body, the body itself being the matter or potentiality. Aristotle completely rejected the mythical thinking of his precursors about the original divinity of the soul, its preexistence, immortality and the imprisonment in the body. Aristotle in De Anima distinguished between the active and passive part of the intellect. Aristotle identified three hierarchical levels of living things: plants, animals, and people, for which groups he identified three corresponding levels of soul, or biological activity: the nutritive activity of growth, sustenance and reproduction which all life shares; the self-willed motive activity and sensory faculties, which only animals and people have in common; and finally reason, of which people alone are capable. In an early dialogue Eudemus (ca. 354 BCE) Aristotle, in the purely Orphic and Platonic spirit, had still accepted the Platonic concept of the temporary imprisonment of the immortal substance
(see also Aristotle's Idea of the Soul, H. Granger, Springer, 2011 and Life's Form: Late Aristotelian Conceptions of the Soul, D. Des Chene, Cornell University Press, 2000).

Aristotle attributed primary importance to the study of the soul as it contributed to the knowledge of the truth and in general to the knowledge of nature. Soul, psyche, is the principle (arche) of living beings. Aristotle in De Anima first delineates the methodological rules and procedural approach to the study. We have to grasp the nature, essence and properties of affections, some of which are proper to the soul and some are proper to the animal. This study is as difficult as to learn about the essence and form of things. Then one has to determine the genre to which the soul belongs and what it is. What is a substance, its category: whether it is a potential thing or it is a certain act (complete reality, fullness). Whether it is divisible or it is indivisible, or they are the same species or they differ generically, or specifically. One should not ignore the other souls e.g. animal's or Divine. Whether there are many souls or many parts of the same soul, so one has to examine the parts and their functions (activity) e.g. intellection or intellect (passive), sensation or the faculty of sensation (active, sensitive faculty).

There is no state or condition of the soul that could be affected without the body, though it seems to be such a function: the intellection. Nevertheless, there is among the functions or affections none that could exist without the body. It is clear that the states of the soul are the forms (logos) realized in matter. The notion (logos) is the form (to eidos) of the thing (pragma), but to be the form it has to be realized in the matter (hule). Thus, properties or functions are inseparable from the bodies. If they are separated, this is done only by abstraction. So the states of the soul cannot be regarded as separable from the physical matter, which is the principle of hylomorphism.

Both Avicenna (ca. 980-1037 CE), Averroes (Ibn Rushd) (1126-1198 CE) and Thomas Aquinas (1225-1274 CE) would follow the Aristotelian model of the soul. The requirements of their Abrahamic religions however would require some modifications of the Aristotelian concept of the soul. Avicenna, taught that, while the Active Intellect is universal and separate, the Passive Intellect is individual and inherent in the soul. Averroes held that both the Active and the Passive Intellect are separate from the individual soul and are universal, that is, one in all men. Averroes in addition speaks of the Acquired Intellect (intellectus acquisitus, adeptus), by which he means the individual mind in communication with the Active Intellect. Thomas Aquinas held that both the Active and the Passive Intellect are part of the individual soul. Pietro Pomponazzi (1462-1525 CE) wrote a treatise De immortalitate animae (E: On the Immortality of the Soul) in the Averroist-Aristotelian tradition.

With the conquests of Megas Alexandros (356-323 BCE) and with the foundation of the Hellenistic empires (by 270 BCE), the Antigonid dynasty, the Seleucid dynasty, the Attalid dynasty and the Ptolemaic dynasty, Greek culture spread from Greece to the Indus and Oriental cultural influences spread to the borders of the Nile in Africa. The Hellenistic civilization followed upon Aristotle and ended with the beginning of Neoplatonism.

One of the first Hellenistic schools to emerge is that of Cynicism, which emphasized denying established conventions and following one's natural inclinations. Their primary interests are ethical, but they conceive of ethics more as a way of living than as a doctrine in need of explication. The end of life is virtue, not pleasure, and it can only be obtained by independence of all earthly possessions and pleasures. As such askēsis, meaning a kind of training of the self or practice, is fundamental. Nature offers the clearest indication of how to live the good life, which is characterized by reason, self-sufficiency, and freedom. Social conventions, however, can hinder the good life by compromising freedom and setting up a code of conduct that is opposed to nature and reason. Conventions are not inherently bad; however, for the Cynic, conventions are often absurd and worthy of ridicule. Only once one has freed oneself from the strictures that impede an ethical life can one be said to be truly free. As such, the Cynics advocate askēsis, or practice, over theory as the means to free oneself from convention, promote self-sufficiency, and live in accord with nature. The Cynics clearly privilege freedom, but not merely in a personal sense as a kind of negative liberty. Instead, freedom is advocated in three related forms: eleutheria, freedom or liberty, autarkeia, self-sufficiency, and parrhēsia, freedom of speech or frankness. In order to live the Cynic life, one had to be inured to the various physical hardships entailed by such freedom. This required a life of constant training, or askēsis
(see also Classical Cynicism: A Critical Study, L. E. Navia, Greenwood Publishing Group, 1996). Examples of ancient cynic philosophers are: Antisthenes (ca. 446-366 BCE), Diogenes of Sinope (ca. 404-323 BCE) and Crates of Thebes (ca. 365-ca. 285 BCE).

Epicureanism

Quod si jam rerum ignorem primordia quae sint,
Hoc tamen ex ipsis caeli rationibus ausim
Confirmare aliisque ex rebus reddere multis,
Nequaquam nobis divinitus esse paratam
Naturam rerum; tanta stat praedita culpa
- Lucretius, De rerum natura, V:195-190 -

The founder and namesake of the Epicurean school was Epicurus (341-270 BCE), who adapted the Atomistic views of Democritus (ca. 460-370 BCE) and held that happiness is achieved through pleasure. In the philosophical system of Epicurean physics was subordinated to ethics. The aim of his philosophy was to overcome irrational fears of natural phenomena and to achieve peace of mind. The goal was to attain a state of tranquility (ataraxia) and freedom from fear, as well as absence of bodily pain (aponia). His philosophy can be summarized in the so-called "Four Herbs of Epicurus": There is nothing to fear from gods, There is nothing to feel in death, Good can be attained, Evil can be endured. According to the Epicureans the gods live in a perfect state of ataraxia (inner peace) and therefore, they do not worry about life in the physical world, not having any influence in people's lives. The difference between gods and humans is that the souls of the gods do not escape from their bodies while the atoms of the human body cannot hold the soul forever. It's humans who worry about the evil, not the gods. The Epicureans stated that the universe is chaos, it has no purpose or intentions and gods have no influence the life of humans, so since people are left alone in a chaotic world, the only way to achieve happiness and peace of mind is by avoiding pain and seeking pleasure (as long as this pleasure does not cause greater suffering). This, according to Epicureans, is the formula to live well in a world without intentionality or purpose. Pleasure that leads to pain should be avoided and pain that leads to pleasure should not be avoided. The goal is to be as free from mental pains as much as is humanly possible and to enjoy ataraxia or tranquillity. Epicurus considered to be pleasure things such as intellectual life, friendship and contact with nature and not bodily sensations, which he considered to bring more pain than pleasure
(see also Epicureanism at the Origins of Modernity, C. Wilson, Oxford University Press, 2008 and Epicurus and the Epicurean Tradition, J. Fish, K. R. Sanders, Cambridge University Press, 2011).

The 40 Principal Doctrines are a summary of his ethical theory. Pleasure means freedom from pain in the body and trouble in the mind. Not all desires are to be satisfied. Most pleasure is to be obtained by living a simple life. On death Epicurus taught: "Thus that which is the most awful of evils, death, is nothing to us, since when we exist there is no death, and when there is death we do not exist". According to Epicurus, the gods do exist, but are patently indifferent to, and uninvolved in human affairs; they also played no role whatsoever in the original creation of the world, nor do they do so in the ongoing workings of nature. Epicurus denied divine providence and argued against the notion that the world is under the providential care of a loving deity by pointing out the manifold suffering in the world. On the Problem of Evil Epicurus put forward the "Epicurean paradox" or "Riddle of Epicurus" in a classical "reductio ad absurdum". The paradox is a trilemma argument (gods are omnipotent, gods are good, but evil exists). For Epicurus, the gods function mainly as ethical ideals, whose lives we can strive to emulate, but whose wrath we need not fear.

Epicurus studied Atomism with Nausiphanes (ca. 325 BCE) who had been a student of Democritus. Epicurus explained natural phenomena by atomism, but he made several modifications to the doctrine in view of Aristotle's criticisms. He distinguished between physical and mathematical divisibility and gave atoms weight. Epicurus argued that as atoms moved through the void like failling raindrops, there were occasions when they would "swerve" (clinamen) from their otherwise determined paths, thus initiating new causal chains - with a 'causa sui' or uncaused cause. This swerve caused collisions and swirls of atoms, and thus worlds were formed. Epicurus wanted to break the causal chain of physical determinism and deny claims that the auture is logically necessary
(see also A Philosophical Examination of Epicurus' Atomism, J. L. Presler, University of Oklahoma, 1973 and Gassendi the Atomist: Advocate of History in an Age of Science, L. S. Joy, Cambridge University Press, 2002, p. 165).

The Roman Titus Lucretius Carus (ca. 99-ca. 55 BCE) wrote the poem De rerum natura on Epicureanism. The first three books provide a fundamental account of being and nothingness, matter and space, the atoms and their movement, the infinity of the universe both as regards time and space, the regularity of reproduction (no prodigies, everything in its proper habitat), the nature of mind (animus, mens, directing thought) and spirit (anima, sentience) as material bodily entities, and their mortality, since, according to Lucretius, they and their functions (consciousness, pain) end with the bodies that contain them and with which they are interwoven. The last three books give an atomic and materialist explanation of phenomena preoccupying human reflection, such as vision and the senses, sex and reproduction, natural forces and agriculture, the heavens, and disease. In book three Lucretius deals with the human mind (animus, mens) and the soul (anima). The soul (anima) is assumed to be made of particularly round "fiery" atoms which are distributed over the body. These special atoms have reflective properties with regard to reality. It is through these atoms that the body receives the impressions or "idols" of exterior things. Everything is constantly throwing off "idols" (a development of Empedocles's "effluences") and these "idols" make contact with the soul atoms whether through touch on the surface of the body or through eye, ear, nose or tongue. So much for ordinary sensation. But there is a particular kind of sensation which we call thought. This sensation may be referred to the mind (animus); for, though the mind and the soul are "the same" in the sense that they are composed of the same round atoms, there is a particularly dense concentration of extremely small "fiery" atoms in the breast which constitute the "animus" or "mens". "Idols" cannot pass through this dense concentration without moving the mind atoms (animus) from which the soul atoms (anima) disperse over the body. Hence thought. The movement of the heart is regarded as being caused by the motions of the "animus" or "mens" atoms. The stronger the movement of the "animus" or "mens", the more the (secondary) soul atoms (anima) disperse throughout the body and have an effect on the body. In this view on the mind and soul of man, there is no place for a mind or soul which exists as a separate meta-entity in its own above and beyond the corpuscules which constitute its parts. The Democritan and Epicurean mind only responds to the circumstances, but does not build an independent meta-reality from its own memories
(see also T. Lucretius Carus, Of the nature of things, Titus Lucretius Carus, J. Matthews for G. Sawbridge, 1714 and De Rerum Natura, W. E. Leonard, S. B. Smith, Univ of Wisconsin Press, 2008).

Epicureanism was suppressed by Christians as they were critical of the apparently selfish nature of Epicurean teachings on pleasure. As a consequence Epicureanism essentially disappeared until it was revived by the Renaissance scholar Lorenzo Valla (1405-1457 CE), who criticized Scholasticism in his Disputazioni dialettiche and supported Epicureanism in De Voluptate (E: On Pleasure). Lorenzo Valla treated Epicureanism as a stepping-stone to the development of a Christian morality based on the concept of pleasure, and repudiated the traditional synthesis of Stoicism and Christianity
(see also Stoicism in Early Christianity, T. Rasimus, T. Engberg-Pedersen, I. Dunderberg, Baker Academic, 2010).

Of all the philosophical schools active during Hellenistic times, Stoicism had the largest number of followers, and was often contrasted with Epicureanism, its closest rival. The founder of stoicism was Zeno of Citium in Cyprus (344-262 BCE), together with Cleanthes (331-232 BCE) and Chrysippus (ca. 280-207 BCE). The works of these early Stoics are lost. We now have to rely mainly on the works of Roman Stoics, such as Seneca (4 BCE-65 CE), Epictetus (ca. 55-135 CE) and the Roman Emperor Marcus Aurelius (121-180 CE). Stoicism shared some aspects with cynicism. Stoicism held that the cosmos is governed by an over-arching fatalistic law, and we best achieve happiness when we resign ourselves to fate. When one's life is aligned with this cosmic purpose, suffering ceases. For the Stoics the universe is perfect and harmonious, therefore, everything that happens, happens to maintain the harmony of the universe. The gods influence people's lives since they work to maintain the harmony of the universe. So humans have to trust that whatever happens, happens for the best, even if some events look evil from the human standpoint. One should change things that can be changed and not worry about what cannot be changed, as all that happens, happens for the best. Pain and suffering also happen for the best even though one may not always like them. Stoic philosophy has several aspects, the three parts of philosophy comprising the classical Stoic curriculum (physics, logic and ethics), the four cardinal virtues (wisdom, courage, justice and temperance) and the practical disciplines as laid out by Epictetus (topoi usch as desire, action and assent). The Stoics divided philosophy into three parts, logic, physics and ethics. These concepts differed from how we deal with them today. Physics not only dealt with natural philosophy, but also with metaphysics and theology. Logic besides formal logic also dealt with rhetoric and epistemology. In the Lives of Eminent Philosophers of Diogenes Laertius (fl. c. 3^rd cent. CE) we find several smilies to explain the the three parts of Stoic philosophy: "Philosophy, they say, is like an animal, Logic corresponding to the bones and sinews, Ethics to the fleshy parts, Physics to the soul. Another simile they use is that of an egg : the shell is Logic, next comes the white, Ethics, and the yolk in the centre is Physics. Or, again, they liken Philosophy to a fertile field : Logic being the encircling fence, Ethics the crop, Physics the soil or the trees. Or, again, to a city strongly walled and governed by reason". Epictetus put forward three disciplines or fields of study (topoi): desire (ὄρεξις, of what is and is not appropriate to want), action (ὁρμή, regarding our relations to others), and assent (συγκατάθεσις, to give to or withdraw from "impressions", i.e., our initial, automatic judgments about the importance of things)
(see also Stoicism, J. Sellars, University of California Press, 2006 and The Stoic Tradition from Antiquity to the Early Middle Ages, M. L. Colish, BRILL, 1990 and Justus Lipsius: the philosophy of Renaissance stoicism, J. L. Saunders, Liberal Arts Press, 1955).

Stoicism evolved from early Stoicism up to the late Stoicism of the Roman empire. Early Stoics like Zeno of Citium in Cyprus (344-262 BCE) taught that the passions and emotions were to be eliminated entirely. Human events which appeared to be tragic or distressing could be seen as leading to some good if the ultimate purposes of divine will were known. Resisting divine will was useless and only resulted in loss of peace of mind. A wise and virtuous man was one who willingly cooperated with divine will and calmly accepted the course of events. Later Stoics responded to the challenge that they were insensitive to human nature by distinguishing between good and bad, or desirable and undesirable apthe. Later Stoics also believed that the universe was created by fire and would be destroyed by fire, before being created again. The goal of Stoicism was to bring the human mind into agreement with the Logos, the impersonal force of reason who formed the universe and to recognise that the Logos did so for mankind's benefit, regardless of personal circumstance. The Logos might be described by a Stoic as "the soul of the universe" (anima mundi) while the physical world was the universe's body. Cleanthes of Assos (ca. 330-ca. 230 BCE) was the successor to Zeno as the second head (scholarch) of the Stoic school in Athens. Among the fragments of Cleanthes' writings which remain, the largest is the Hymn to Zeus in which he considered the universe a living being and said that Zeus was the soul of the universe and the sun its heart. Zeus for Cleanthes orders the world as an immanent force that both combines bad with good in a permanent union of opposites and enables humans to change from bad to good. Cleanthes formulated the Stoic formula that the goal of life is "to live consistently with nature".

Panaetius (ca. 185-109 BCE) rejected the doctrine of apatheia and replaced it with the more Aristotelian ideal of moderation and self-control, suggesting that some of the "goods" in this world might be valuable and worth pursuing for their own sake. Panaetius taught Scipio (185-129 BCE) and many others of the Roman nobility the principles of Stoicism. In his work De Officiis Panaetius laid down the central ideas of Stoicism; that man is a part of a whole, that he is here not to enjoy the pleasures of the sense, but to do his duty without complaint. De Officiis was the principal source used by Marcus Tullius Cicero (106-43 BCE) in his own work of the same title. Educated Romans grasped at this philosophy as dignified and presentable. They found in its ethics a moral code completely congenial to their ancient traditions and ideals. Stoicism became the inspiration of Scipio, the consolation of Marcus Aurelius (121-180 CE), and the conscience of Rome. During the Roman period, Seneca (4 BCE-65 CE), Epictetus (ca. 55-135 CE) and the Roman Emperor Marcus Aurelius (121-180 CE) were notable stoics. From Seneca we have the Epistulae Morales ad Lucilium, from Epictetus we have the Discourses and from Marcus Aurelius we have his Meditations.

The Discourses of Epictetus were transcribed and compiled by his pupil Arrian (ca. AD 86/89-after 146/160 CE). His teachings were brought together in the Discourses (Ἐπικτήτου διατριβαί) and the Enchiridion (Ἐγχειρίδιον Ἐπικτήτου). In the Enchiridion Epictetus put forward: "To avoid unhappiness, frustration, and disappointment, we, therefore, need to do two things: control those things that are within our power (namely our beliefs, judgments, desires , and attitudes) and be indifferent or apathetic to those things which are not in our power (namely, things external to us"). The same stoic principles can be found in the modern day Serenity Prayer. As a Stoic teacher Epictetus put forward three topoi (fields of study) in which the prokoptôn (Stoic student) applies the Stoic principles; they are practical exercises or disciplines that when successfully followed are constitutive of the eudaimôn state of life. The first topos is the discipline of assent, the second is the discipline of desire, and the third one is the discipline of action. The three topoi correspond with the three fundamental faculties of the human soul which are desire (orexis), will (hormè) and representation (phantasia). The three topoi define the three fundamental aspects of askesis or spiritual excercise. The first would put man in accordance with the universe (ataraxia), the second deals with the relation with other people (justice and love) and the last one puts man in accordance with himself (love of truth). The prokoptôn should practice prosochē as part of his spiritual exercises. Prosochē (προσοχή), the attitude and practice of attention, is the fundamental Stoic spiritual attitude. Prosochē is a state of continuous, vigilant, and unrelenting attentiveness to oneself-the present impressions, present desires, and present actions which shape one's moral character (prohairesis). In Stoicism prosoche broadly refered to the discipline of "attention" or mindfulness, noticing the judgements that we make about ourselves and the world, observing whether or not they are in conformity with the reality of our situation, and correcting them so as to maintain appropriate behaviour and equilibrium (ataraxia). Prosochē can be compared to the Buddhist practice of mindfulness or sati. Mindfulness is the ability to see things as they really are, without the cloud of feelings, prejudice, or even mood. We find a similar approach to spiritual exercises as the Discourses in the Exercitia spiritualia of Ignatius of Loyola. Reaching spiritual equilibrium for the Stoic means achieving apateia or complete absence of passions (orexis) which no longer distracts man. The Meditations of Marcus Aurelius are about his ideas on Stoic philosophy. They are spiritual exercises in which Marcus Aurelius meditates about the Stoic way of life (manière de vivre). Throughout his Meditations, Marcus Aurelius teaches us to narrow the focus of our attention to the present, our present representations, present impulses, and present actions. He puts forward that only our present thoughts and actions are within our control, and the past and future are indifferents. Man should not be bothered with those aspects of life which do not depend on himself, but lead a virtuous life by focusing on those things which do depend on himself. His meditations follow the triune structure of the three topoi of Epictetus, where man seeks accord with the cosmos, other men and with(in) himself
(see also Exercices spirituels et philosophie antique, Pierre Hadot, Etudes augustiniennes, 1981 and Philosophy as a Way of Life, Pierre Hadot, Blackwell Publishing , 1995, p. 84 and La Citadelle intérieure, Pierre Hadot, Fayard, 1992 and Prosochē: Illuminating the Path of the Prokoptōn, Christopher Fisher, on-line and Meditatio - Refashioning the Self: Theory and Practice in Late Medieval and Early Modern Intellectual Culture, Karl A. E.. Enenkel, Walter Melion, BRILL, 2010, p. 2 and Cartesian Philosophy and the Flesh: Reflections on incarnation in analytical psychology, Frances Gray, Routledge, 2013, p. 36).

For both Epicureanism and Stoicism, the key for happiness is moderation, only for different reasons. For Stoics, moderation was a way to be aligned with the universe's will (Nature) and for Epicureans, moderation was the best way to avoid pain.

Stoic philosophy is primarily concerned with ethics. Stoic ethics is based on an understanding of the nature of living beings and as such derived from its physics. Nature consists of a hierarchy of powers which are based on the activity and organization of the πνεῦμα (pneuma, spirit, soul) which flows though the entire cosmos. The level of organization of pneuma differs for inanimate and animate things. Non-rational animals have ἕξις (hexis, cohesive state), φύσις (phusis, organic nature), and ψυχή (psuchê, soul). Human beings (and gods) possess the highest level of pneumatic activity: λόγος (logos, reason). Stoicism founds it ethics on the concept of οἰκείωσις (oikeiôsis, orientation , appropriation). For Stoics the basic desire in all non-rational and human beings is self-preservation. Oikeiôsis is the foundation for all animal impulses as well as human ethical action. Oikeiôsis is a process of natural moral evolution by which man comes to recognize the value of reason in its own right and thus learns how to make proper moral judgments. From this basis of self-preservation we consider good those things which are beneficial for our self-preservation and bad which causes harm. For non-rational animals good things are limited to food, water , shelter, etc. . For a rational being like man his survival as a rational being is also important, not merely surviving like an animal. Besides his body man, as a rational being, must also take care of his soul, which leads to cultivating ἀρετή (virtue, excellence) which is the only thing which is equivocally good in order to achieve εὐδαιμονία (well-being, flourishing). Virtue is the only reference for morality, everything else is considered morally indifferent (see The Stoic Theory of Oikeiosis: Moral Development and Social Interaction in Early Stoic Philosophy, Troels Engberg-Pedersen, Aarhus University Press, 1990 and The Oxford Handbook of the History of Political Philosophy, George Klosko, OUP Oxford, 2011, p. 139 and Stoic Ethics: Epictetus and Happiness as Freedom, William O. Stephens, A&C Black, 2007 and Stoicism, John Sellars, Routledge, 2014, pp; 107-134).

Stoic ethics is a virtue ethics, which is primarily concerned with helping one person become a better person though self-improvement. The perfected nature of a rational being is the perfection of reason, and the perfection of reason is virtue (ἀρετή). Virtue is the only thing that always contributes to happiness, as it is the only necessary and sufficient condition for happiness. Stoicism divides everything which exists in three groups: good, bad and ἀδιάφορα (adiaphora, indifferent things). Within the indifferent things stoicism distinguishes between προηγμένα (proêgmena, preferred indifferents), which help us living according to Nature (e.g. health) and ἀπροηγμένα (aproêgmena, dispreferred indifferents), which hinder our living according to Nature (e.g. illness). Good and evil are only to be found in man, in our προαίρεσις (prohairesis, reasoned choice) not in external things. The only things that are good are virtue and those things which participate in virtue, everything else is to be regarded with indifference. With regard to indifferent things Stoicism put forward the dichotomy of control as in the Enchiridion (1): "Some things are within our power, while others are not. Within our power are opinion, motivation, desire, aversion, and, in a word, whatever is of our own doing; not within our power are our body, our property, reputation, office, and, in a word, whatever is not of our own doing." For stoics things outside of our control are not 'up to us' as we only control our opinions, impulses, desires, and aversions, nothing more. Man should be indifferent to events which are outside of our control as they are neither good nor bad (ἀδιάφορα, indifferent things) and not worthwhile to be desired, pursued or being disturbed by (see Stoicism, John Sellars, Routledge, 2014, pp; 107-134).

The end or purpose of life is arete (excellence) or virtue, which is roughly identified with "happiness". Stoic philosophy is regarded as a medicine for the soul which is to be practiced, not only read: "Non est philosophia populare artificium nec ostentationi paratum. Non in verbis sed in rebus est. Nec in hoc adhibetur, ut cum aliqua oblectatione consumatur dies, ut dematur otio nausea: Animum format et fabricat, vitam disponit, actiones regit, agenda et omittenda demonstrat, sedet ad gubernaculum et per ancipitia fluctuantium derigit cursum. Sine hac nemo intrepide potest vivere, nemo secure: innumerabilia accidunt singulis horis quae consilium exigant, quod ab hac petendum est" (Seneca, Epistulae Morales ad Lucilium Liber II, XVI, 3). The central theme of stoicism is "indifference to external circumstances". Apatheia (freedom from the passions, equanimity of soul) was the Stoic understanding of happiness and ataraxia (freedom from disturbance) was the Epicurean idea. Apatheia signifies a condition of being totally free from the pathe, emotions and passions such as pain, fear, desire, and pleasure. Apatheia represented a state of tranquility and peace of mind, achieved by becoming indifferent to pleasure or pain and conforming to the inevitable course of events, which was governed by divine will. Stoicism states that man should "live life according to nature" and our actions should agree with the laws of nature. Stoics assumed the doctrine of (soft) determinism. In the external world, every event has a cause; there are no exceptions, but we do have some control over our mental events. Since we are rational, we can know the laws of nature and can consciously follow them-rather than seek to overcome them or wish the laws were different. Stoicism states that we are different from our emotions. Emotions are the result of the perception of an external situation considered with the attendant bodily states. The dangers of the identification of the ego with the emotions include loss of personal freedom. Character, truly virtuous conduct, and fulfillment of duty, are the points most stressed in Stoic ethics.

The goal of Stoicism was to become a σοφός (wise person, virtuous sage). However, the Stoic sage was understood to be an inaccessible ideal rather than a concrete reality. Achieving εὐδαιμονία consisted in cultivating one's moral virtues in order to become a good person. The four cardinal (moral) virtues of Stoicism were: σοφίᾱ (wisdom), ἀνδρεία (courage), δῐκαιοσῠ́νη (justice), and σωφροσύνη (temperance). Stoics practiced what are known as "spiritual exercises" and drew upon them for strength. These spiritual exercises were an invitation to a new way of life, active reflection, and living consciousness. They used writing meditation (hypomnematas) and προσοχή (prosochê) or the art of attention. The Τὰ εἰς ἑαυτόν (Meditations) of Marcus Aurelius (121-180 CE) are an example of writing meditation (hypomnemata). The Ἐγχειρίδιον of Epictetus (55-135 CE) contains Stoic ethical advice. Stoicism deals with three fields (physics, logic and ethics) and three disciplines (desire, action, and assent) and is meant to be applied to everyday living, focused on ethics, inspired by physics (a combination of natural science and metaphysics) and logic. Epictetus (55-135 CE) dealt with the three disciplines, which are meant to be practiced by the προκόπτων (prokoptôn, Stoic student). In his Discourses (III.2, 1-3a) he put it this way: "There are three things in which a man ought to exercise himself who would be wise and good. The first concerns the desires and the aversions, that a man may not fail to get what he desires, and that he may not fall into that which he does not desire. The second concerns the movements (toward) and the movements from an object, and generally in doing what a man ought to do, that he may act according to order, to reason, and not carelessly. The third thing concerns freedom from deception and rashness in judgment, and generally it concerns the assents. Of these areas, the chief and most urgent is the first which has to do with the passions, for strong emotions arise only when we fail in our desires and aversions" Epictetus also emphasized the importance of μελετάω (practice) and ἀσκέω (training) besides μανθάνω (study): "That's why the philosophers warn us not to be satisfied with mere learning, but to add practice and then training. For as time passes we forget what we learned and end up doing the opposite, and hold opinions the opposite of what we should." (Discourses, II.9, 13-14). The three topoi (places, Stoic fields of study) establish activities in which the prokoptôn (Stoic student) applies the Stoic principles, which are practical exercises or disciplines that when successfully followed are constitutive of the eudaimôn (beautiful) life. These topoi (places) are also a way to approach a topic from different angles, in order to understand an issue more fully (here life itself). The prokoptôn practices προσοχή or the attitude and practice of attention, which is a state of continuous, vigilant, and unrelenting attentiveness to oneself (προαίρεσις). The three topoi are, according to Epictetus (55-135 CE):

1. Desires (ὄρεξις) and aversions (ἔκκλισις) - perception
2. Impulse to act (ὁρμή) and not to act (ἀφορμή) - action
3. Freedom from deception, hasty judgement, and anything else related to assents (συγκατάθεσις) - will

For the stoics the universe started with a Primordial Fire and the wold is made of matter (materialism). Causation is universal and the universe in organized rationally (Logos). Life is to be lived according to human Nature, which is socially and rational.

For stoicism Nature is rational and the universe is governed by the law of reason (Logos, providence, pronoia). Man can't actually escape its inexorable force, but he can, uniquely, follow the law deliberately (determinism). A virtuous life in stoicism relates to a life led according to rational nature (prudence, φρόνησις). Only virtue and vice are good or bad as they are only dependent on ourselves, as they are the basic choices of one's path in life. For the stoics the world was built, by an immanent God, out of four elements, from which two are active (fire and air) and two are passive (water and earth). Fire and air combine to form breath or pneuma, which is the sustaining cause (causa continens, synektikon aition) of all existing bodies. The human soul was believed to be this hot fiery breath (pneuma), which infused the physical body of man. The human soul consisted of eight parts, the five senses, the reproductive faculty, the speech faculty, and the central commanding faculty or hêgemonikon (ἡγεμονικόν). The hêgemonikon was the central facility which received and organized the impressions of phantasia, or imagination, delivered by the senses. The hêgemonikon manifests four mental powers: the capacity to receive impressions (phantasia, φαντασία), to assent to them, form intentions to act in response to them, and to do these things rationally. Perception or kataleptic phantasia φαντασία καταληπτική), means one's state of mind as it relates to grasping fundamental philosophical concepts. In his Discourses (Ἐπικτήτου διατριβαί), Epictetus (ca. 55-135 CE) wrote about keeping the prohairesis (προαίρεσις) and the hêgemonikon in the right condition meaning aligned to the logos. For Epictetus prohairesis and hêgemonikon are essentially interchangeable. Wisdom (σοφία or theoretical wisdom) is regarded to be the root virtue. Becoming a clear and unbiased thinker allows one to understand the universal reason (logos). Wisdom (σοφία) was a combination of nous (intuitive understanding) and episteme (scientific knowledge). In order to be wise, first of all one has to understand the way the world works, its physics, and understand one's place in it. Not understanding one's place in the world leads to foolishness, because one begins to wish for things that are not in accordance with the logos of nature. For stoics, science (physics) precedes morality (virtue) and both are closely related. From wisdom (σοφία) spring the four cardinal virtues of stoicism: practical wisdom (φρόνησις), courage (ἀνδρεία), justice (δικαιοσύνη) and temperance (σωφροσύνη). Since passion is irrational, life should be waged as a battle against it. Intense feeling should be avoided which leads the stoic to apatheia (equanimity of soul). Apatheia is the kind of calm equanimity that comes with the absence of irrational or extreme emotions. It does not mean the loss of feeling altogether, just the loss of the harmful, unhelpful kind. A stoic develops self-control and fortitude as a means of overcoming destructive emotions. Pleasure is not good, but nor is it bad (indifference). Pleasure is only acceptable if it doesn't interfere with the quest for virtue (principle of false dogmata). Poverty, illness, and death are not evil, they a indifferent as they are beyond our control. Virtue should be sought, not for the sake of pleasure, but for duty. With regard to interpersonal relations, stoicism emphasizes the equality of man, because all men alike are products of nature
(see also The Tenets of Stoicism, Assembled and Systematized, Hamilton Baird Timothy, Lucius Annaeus Seneca, Coronet Books Incorporated, 1973 and The Cambridge Companion to the Stoics, Brad Inwood, Cambridge University Press, 2003, p. 179 and History of the Concept of Mind: Speculations about soul, mind, and spirit from Homer to Hume, Paul S. MacDonald, Ashgate, 2007, p. 75 and The Therapy of Desire: Theory and Practice in Hellenistic Ethics, Martha C. Nussbaum, Princeton University Press, 2013, p. 359 and Studies in Stoicism, P. A. Brunt, Miriam Griffin, Michael Crawford, Alison Samuels, OUP Oxford, 2013, p. 462 and Plato and the Stoics, A. G. Long, Cambridge University Press, 2013, p. 11).

The fundamental proposition of Stoic physics is that "nothing incorporeal exists" and so there is no noematic plane besides the noetic plane of reality. This materialism coheres with the sense-impression orientation of their doctrine of knowledge. The Stoics, place knowledge in physical sensation, and reality - what is known by the senses - is matter. The stoics retained Aristotle's plenistic physics (horror vacui) and argued for the indefinite divisibility of matter as opposed to the Atomists. Stoics stressed the analogy between macrocosm and microcosm, the heaven and the earth. They also distinguished between inert matter and a more active form, the latter being called the pneuma, or vital spirit. Pneuma pervaded the whole cosmos and brought about generation as well as decay. Ordinary substances, as Empedocles (ca. 495-435 BCE) and Aristotle (384-322 BCE) had taught, were composed from the four elements, albeit hot and dry, fire and air were more active than passive earth and water into cohesive substances
(see also The Origins of Stoic Physics, D. E. Hahm, University of Wisconsin, 1966 and Alexander of Aphrodisias on Stoic Physics, R. B. Todd, BRILL, 1976 and The Cambridge Companion to the Stoics, B. Inwood, Cambridge University Press, 2003, p. 153).

The Stoics developed a propositional logic, different from the Aristotelian logic of the peripatetics. For Stoics, knowledge can be attained through reason, in principle capable of distinguishing true from false.

The main difference with Aristotelian logic lies in the fact that in the Stoic syllogisms the variables are propositional variables, while in Aristotelian logic they are term variables (see Stoic Logic: The Dialectic from Zeno to Chrysippus). Aristotelian logic is founded on premises or definitions, while Stoic logic starts from facts (physics). Aristotelian syllogisms are called 'categorical syllogisms', while 'hypothetical syllogisms' is used not only for those syllogisms introduced by the peripatetics Theophrastus of Eresus (ca. 371-ca. 287 BCE) and Eudemus of Rhodes (ca. 370-ca. 300 BCE), but also the Logic of the Stoics. The Stoics concerned themselves with predicate logic (term-logic), but their main achievement was the development of a propositional logic or sentential logic, i.e. of a system of deduction in which the smallest substantial unanalyzed expressions are propositions, or rather, assertibles. The domain of propositional logic is primarily the study of logical operators and it does not deal with logical relationships and properties that involve the parts of a statement smaller than the simple statements making it up. Propositional logic mainly deals with studying statement operators such as "and", "or" and "if... then...". Chrysippus of Soli (ca. 280-207 CE) developed a kind of propositional logic as an alternative to Aristotelian logic. The subject matter of Stoic logic are the so-called sayables (lekta), which are the underlying meanings in everything we say and think. What we utter are spoken and written linguistic expressions, but what we say are the sayables. The Stoics made a distinction between using and mentioning, meaning that every denoting expression is ambiguous in that it denotes both its denotation ('literal' meaning) and itself. The distinguish between deficient and complete sayables, where the complete sayables include include assertibles (the Stoic equivalent for propositions). Assertibles (axiômata) differ from all other complete sayables in their having a truth-value. Truth is temporal and assertibles may change their truth-value. The assertibles can be simple or non-simple. Assertibles however can be bivalent, leading to paradoxes such as the Liar and the Sorites (little-by-little arguments) paradoxes. An assertible is possible when it is both capable of being true and not hindered by external things from being true and it is impossible when these condition are not met. Arguments are constructed as compounds of assertibles and consist of at least two premises and a conclusion. Stoic syllogistic is an argumental deductive system consisting of five types of indemonstrables or axiomatic arguments and four inference rules, called themata: modus ponens, modus tollens, modus ponendo tollens, and modus tollendo ponens. Non-evident formally valid arguments are reduced by means of accepted inference rules to evidently valid arguments
(see also Stoicism, J. Sellars, University of California Press, 2006, p. 55 and Hypothetical Syllogistic and Stoic Logic, A. N. Speca, BRILL, 2001 and Logic Made Easy: How to Know When Language Deceives You, D. J. Bennett, W. W. Norton & Company, 2005, Ch. 'Hypothetical syllogisms')

A fourth major philosophical school of the Hellenistic period was Skepticism, which, as its name implies, emphasized doubting everything, specifically as a means of becoming tranquil and happy. The two main varieties of ancient skepticism are Academic and Pyrrhonian skepticism. Academic skepticism originated out of Plato's Academy during its skeptical period (ca. 273 BCE to 1st century BCE) and started with Arcesilaus (316/5-241/0 BCE) in his role as leader of the Academy (266/268 BCE). Carneades (214-129/8 BCE) was another Academic skeptic. Pyrrhonian skepticism originates from Pyrrho (ca. 365-270 BCE). Pyrrho was frustrated with the assertions of the Dogmatists (those who claimed to possess knowledge), and founded a new school in which he taught fallibilism, namely that every object of human knowledge involves uncertainty. Pyrrhonism aims at tranquility; and it assigns pride of place to appearances. Timon of Phlius (ca. 320-ca. 230 BCE) a pupil of Pyrrho was also a noted skeptic. Sextus Empiricus (ca. 160-210 CE) left us the most complete surviving account of ancient Greek and Roman skepticism. He raised concerns which applied to all types of knowledge and he doubted the validity of induction. His philosophy became known as Pyrrhonian skepticism which differs from the Academic (Platonic) skepticism. Skepticism was revived in Early Modern times by philosophers such as Desiderius Erasmus of Rotterdam (1466-1536 CE) and Michel de Montaigne (1533-1592 CE)
(see also Philosophical Skepticism, C. Landesman, R. Meeks, John Wiley & Sons, 2008 and Pyrrhonian Skepticism, W. Sinnott-Armstrong, Oxford University Press, 2004 and Montaigne and the Rise of Skepticism in Early Modern Europe: A Reappraisal, Z. S. Schiffman, Journal of the History of Ideas 45, no. 4 (1984), pp. 499-516 and The History of Scepticism from Erasmus to Spinoza, R. H. Popkin, University of California Press, 1979).

The final Hellenistic and the first Imperial school is Neoplatonism, which held that there is a single source of all reality from which every existing thing radiates, like rays radiating out from the sun. At the time, philosophers of this school saw themselves simply as Platonists, that is followers of Plato's philosophy. The term Neoplatonism is a recent creation, which suggests that these philosophers adapted Plato's theory, rather than just followed it. While several Hellenistic philosophers can be classified as Neoplatonists, there is one undisputed leader: Plotinus (204/5-270 CE). The origins of Neoplatonism can be traced back to the era of Hellenistic syncretism which spawned such movements and schools of thought as Gnosticism and the Hermetic tradition
(see also A History of Ancient Philosophy: The Schools of the Imperial Age, G. Reale, SUNY Press, 1990 and The Neoplatonists, J. Gregory, Routledge Chapman & Hall, 1999 and Neoplatonism, P. Remes, University of California Press, 2008).

Plotinus (204/5-270 CE), was the founder of Neoplatonism, and is one of the most influential philosophers in antiquity after Plato and Aristotle. He wrote the Enneads, in which he explains about the three basic principles of his metaphysics, which are called by him 'the One' (or, equivalently, 'beauty' or 'the Good'), Mind (Intellect), and Soul. Neoplatonists believed in a structural scheme of levels of reality, related by emanation, in which the higher orders both cause and unify the lower, as the soul gives life to, and unifies, the body it inhabits. By a process of overflow, or emanation, the One generates the next order of being, Mind (Intellect), which contains the Forms as its Ideas. Mind, in turn, generates the World Soul by emanation. Finally, although the generative power is now weak, Nature and Matter appear, shadowy and imperfect, at the bottom of the Fountain of Being, thereby creating the Great Chain of Being
(see also The Great Chain of Being, A. Oncken Lovejoy, Transaction Publishers, 2009, p. 61). Plotinus' philosophy is less oriented towards practical life and rather designated to lead the way (back) towards the Good in which a likeness to the One is of course the highest end possible. This ascent to the One takes place through means of contemplation. His famous last words are said to read as follows: "Try to bring back the God in yourself to the God in the All"
(see also The Cambridge Companion to Plotinus, L. P. Gerson, Cambridge University Press, 1996 and Reading Plotinus: A Practical Introduction to Neoplatonism, K. Corrigan, Purdue University Press, 2005).

The Neoplatonism of Plotinus and Porphyry of Tyre (234-ca. 305 CE) is still considered to be orthodox Platonic philosophy, which distinguishes it from later movements of Neoplatonism, such as those of Iamblichus (ca. 245-ca. 325 CE) and Proclus (412-485 CE). Porphyry wrote the Philosophos historia and the Vita Pythagorae. He was also involved in the controversy with early Christianity as shown in his De Philosophia ex Oraculis Haurienda and his Adversus Christianos
(see also Porphyry's Against the Christians, R. J. Hoffmann, Prometheus Books, Publishers, 1994).

Iamblichus (ca. 245-ca. 325 CE) at the head of his system placed the transcendent incommunicable "One", the monad, whose first principle is intellect, nous. Immediately after the absolute One, lamblichus introduced a second superexistent "One" to stand between it and 'the many' as the producer of intellect, or soul, psyche. This is the initial dyad. The first and highest One (nous), which Plotinus represented under the three stages of (objective) being, (subjective) life, and (realized) intellect, is distinguished by Iamblichus into spheres of intelligible and intellective, the latter sphere being the domain of thought, the former of the objects of thought. These three entities, the psyche, and the nous split into the intelligible and the intellective, form a triad. This triad would in the end evolve into the Christian Trinity. The whole of Iamblichus"s philosophy is ruled by a mathematical formalism of triad, hebdomad, etc., while the first principle is identified with the monad, dyad and triad; symbolic meanings being also assigned to the other numbers. Iamblichus with his philosophy had salvation as his final goal. The embodied soul was to return to divinity by performing certain rites, or theurgy, literally, 'divine-working'. According to Iamblichus, the theurgist eventually reaches the level where the soul's inner divinity unites with 'The One'. Iamblichus most important works are Theurgia or On the Mysteries of Egypt, in which he attempted to give Neoplatonic theurgy a philosophical basis, and De vita Pythagorica liber on the life of Pythagoras.

Proclus (412-485 CE) wrote may commentaries on the works of Plato and other philosophers, such as his commentary Procli Diadochi in Primum Euclidis Elementorum Librum Commentarii on the First Book of Euclid's Elements, which offers penetrating insight on the nature of mathematical being, showing how the Platonic Ideas of the mathematical concepts are received by the mind (nous) and projected onto the imagination, which serves as a mirror for the reflections of the soul. Geometrical figures are therefore rightly understood as doorways into the Ideal World. Contemplation of the relation between the figures and the Ideas can lead us into the Via Mathesis, that is, the spiritual path of self-knowledge gained through mathematical insight. Proclus also wrote the Elements of Theology and the Platonic Theology. The Elements of Theology, which consists of 211 propositions and proofs arranged in a strict order of scientific exposition, can be considered as the most important exposition of Proclian philosophy. In this work he proceeds 'more geometrica' in order to elaborate a conceptual metaphysics based on the postulates of Platonism and Greek geometrical logic. Proclus' more geometrico includes the analytic road to principles as part of anamnēsis. Proclus's Neoplatonic doctrine is an emanative system in which the entire scope of reality spreads between 'The One', the absolute principle above "being" itself, and first matter (prima materia), the final emanation of the One. Proclus in his works on Plato asserts that the whole of Plato's doctrine is contained in the Parmenides presenting the world of intelligibles and the Timaeus the world of sense. For Proclus the two are intimately correlated in as much as "the sensibles are in the intelligibles paradigmatically and the intelligibles in the sensibles after the manner of images" (sensibles acting as symbols pointing to the intelligibles). For Proclus the objective of dialectic 'more geometrica' is to deduce all truth from a single transcendental truth and to proceed back and forth from 'The One' to the world of 'intelligibles' and 'intelligibles', which constitutes the 'Great Chain of Being'. For Proclus there is a need of a certain catharsis by which the soul may be freed from sensible reality in order to consider the divine truths in an ascending scale of comprehension. For Proclus the philosophy of Plato, besides being divinely inspired, also constitutes a system which is primarily verifiable in a man's examination of his own interior experience of the truth. According to Proclus the philosophical ascent towards Platonic wisdom, requires certain moral and intellectual predispositions. The origin of philosophy for Proclus lies in discovering the truths of ethics, inasmuch as all true philosophical speculation must depend upon a removal of the impediments to knowledge incurred in the soul's descent to generation and its consequent preoccupation with the irrational side of human life. The philosopher uses three approaches dialectic (mathematics, reasononing 'more geometrica', logic), maieutic (Socratic method), and erotic (longing for the Good) for the Neoplatonic ascent towards 'The One'. The intellectual predispositions required for the study of Platonic wisdom are those arts which train the mind to think apart from sense and imagination. Mathematical disciplines for Proclus are given preeminence over the other arts, which he regards as a propaedeutic to philosophy. Mathematics is in itself surpassed by dialectic or philosophical questioning in which the strict science of logic is already supposed. Mathematics therefore is not sufficient, but prepares the way for 'anamnesis'. Morality is seen as a way or method to abstract from the passions, and through an education emphasizing "pure" speculation, the disciple is prepared to attend to the nature of his spiritual soul and to its eternal ideas, and in particular he is predisposed to think according to analogy. The truth of Platonism becomes apparent in the analysis of the modes of knowledge, which are defined as opinion (doxa), science (episteme), and faith (pistis). Man's original experience of the objects of his sense and his imagination is the source of the first general mode of knowledge, which is opinion. Opinion (doxa), which we may understand as the judgement utilizing concepts derived from the objects of sensation, can be false as well as true
(see also The Six Books of Proclus, the Platonic Successor, On the Theology of Plato 3 Vol., Thomas Taylor ed. and tr., London, 1816 and Proclus on human reality, Douglass McFerran, MA, Thesis, 1959 and The Routledge Handbook of Neoplatonism, Svetla Slaveva-Griffin, Pauliina Remes, Routledge, 2014, p. 149 and Rhetoric More Geometrico in Proclus' "Elements of Theology" and Boethius' "De Hebdomadibus", Institute for Christian Studies (Canada), 2008 and Plato's Theory of Ideas, William David Ross, Clarendon press, 1951, pp. 91 and 100-101 and Commentarium in Platonis Primum Alcibiadem in Procli Philosophi Platonici opera inedita, Victor Cousin ed., 2nd ed., Paris, 1894, col. 293 and Commentarium in Platonis Parmenidem in Procli Philosophi Platonici opera inedita, Victor Cousin ed., 2nd ed., Paris, 1894, op. cit., col. 321-324).

Neoplatonists challenge the Aristotelian supposition that the ideal world of the Platonic 'Forms' can be substituted for by a material world known through abstraction from sense data as this does not surpass the level of 'dodxa'. The forms of things participate in being, but because they exist merely as multiplied images and they cannot be said to be essences of themselves. The Platonic essence of Being is one and is not subject to material conditions and it cannot exist in individuals which are in themselves something in the order of coming-to-be and passing-away. For the late Platonists of the Academy Aristotle is satisfied in thinking that the highest science consists in the knowledge of the unmoved movers, the immaterial beings which are the source of all motion. However contemplation of the chain of motion for the sake of which something is done is by no means an end in itself; it is intrinsically subordinated to the sole absolute of union with the Good. Neoplatonists make a disctinction between the world of Becoming apprehended by sense and the world of Being coordinate with some subsistent intellect. They also put forward the dependence of the world of Becoming on the world of being for what existence and knowability it possesses. It is necessary that there be an intelligent efficient cause responsible for the existence of the material world, i.e. the Demiurge as the Architect of the Universe. The Platonists begin with unity in order to explain plurality, while Aristotle starts with plurality in order to explain unity. Aristotle departed from Plato in the matter of an extreme realism 'ante res' for a more moderate realism 'in res'. This approach was rejected by the late Platonists or Neoplatonists. They rejected the positive Aristotelian view on the world of material actualization. As the human soul emanates from 'The One' through the 'Intellect', life can be seen as an attempt to return to the lost unity by means of remembering or anamnesis. The human soul on one hand lives in itself and knows itself (i.e. it moves itself) and it also lives in the body and knows through the sense organs of the body (i.e. it moves the corporeal nature dependent on it). The soul is intelligent, i.e. potentially knowing, because of its being an emanation of a separate Intellect, and it is actually knowing when it converts itself or returns to Intellect. For Proclus, like Plato, there are two path towards knowing which are learning (mathêsis) and discovery (heuresis). Both mathêsis and heuresis constitute the anamnêsis or recollection, which is the Socratic midwifery or maieutic aspect of philosophy. The Socratic method is meant to make one 'remember' which is hidden in the soul. The fulfillment of anamnêsis is in "eidetic intuition" which is insight into the essence which is in itself is grasping an eidos or a Form. Here we make a distinction between the capability of reason to deal with the objects of sensation in order to produce "physical reasons" (physikoi logoi), secondary noêmata or concepts (hysterogenê) which only represent the common characteristics of material things and conceptualization and imagination. Reason as conceptualization deals with the "psychic reasons" (psychikoi logoi) or "inborn" mental counterparts of the Ideas paradigmatically responsible for sensible objects. Intellection then consists in an "attention" to or participation in these innate ideas or primary noêmata or intelligibilities. In this view a pure intellect is identified not accidentally but substantially with primary noêmata, not potentially but actually. Science as epistêmê (ἐπιστήμη) or true knowledge is versed with the objects of intelligence and reason, as distinguished from opinion (doxa from δοκεῖν). Epistêmê or science does not consist in judging according to hysterogenê but attends to the essential or "being-like" differences of these psychic reasons, viewing in them the pattern of the ideal world of the 'Forms' itself. The transcendent Ideas of Platonism are the intelligible essences prior to the thought of the Demiurge and therefore closer to 'Good' or the 'The One'. Ultimately one reaches the first of the three triads of intelligibles constituting the first order of progression from 'The One'. Noěsis (νοῦς) then is the act of intellection respecting things-in-themselves is a simple intuition of the undivided intelligibilities. Dianoia (διάνοια) on the other hand is the act of reasoning, which is a movement employing definite methods like compositions and divisions, definitions and demonstrations, in order to attain the first principles and to deduce the necessary conclusions constituting epistěmě or science. Epistêmê then respects the same intelligible objects as noêsis and dianoia, but the soul in the act of intellection transcends the activity of rational inquiry (dialaectic reasoning) in a contemplation of the pure Ideas or eternal truth, using the innate ideas as an intermediary. Philosophy in the end not only means the soul returning to know itself, but also its remote causes (Life and Being beyond and above Becoming) and ultimately 'The One' itself. The ultimate goal of the process is 'The One' which is also the Good. In returning upon itself the soul is able to know not only itself but also its causes, and through its consideration of the process of procession and return the soul may attain to a knowledge of the structure of reality as poised between the absolute One, where return is at an end, and first matter, where procession is at an end
(see also Proclus on human reality, Douglass McFerran, MA, Thesis, 1959 and Platonic Theology, Proclus, In Metaphysica Commentaria, Syrianus, ed. William Kroll ed., Berlin, 1902, p. 23 and pp. 12-13 and Introduction to Phenomenology, Robert Sokolowski, Cambridge University Press, 2000, p. 12

Neoplatonism was introduced in the Latin West through a Latin translation of Plotinus by Victorinus (fl. c.361), which greatly influenced Augustine of Hippo (354-430 CE). Christianity, which had at this time no clearly developed philosophical structure of its own, found in Neoplatonism the metaphysical system needed to provide the intellectual background for its theological beliefs. Although the primary source for this background was Augustine, the writings of Pseudo-Dionysius the Areopagite and Anicius Manlius Severinus Boethius also played an important role. Until the 13^th century, when renewed attention to the works of Aristotle offered an alternative, Neoplatonism remained the philosophical foundation for Western Christianity. Pseudo-Dionysius the Areopagite (late 5^th to early 6^th century) was the author of the Neoplatonic Corpus Areopagiticum in which he transposed the whole of Pagan Neoplatonism from Plotinus to Proclus, but especially that of Proclus and the Platonic Academy in Athens, into a Neoplatonic form of Christianity
(see also The Significance of Neoplatonism, R. Baine Harris, SUNY Press, 1976, p. 15 and A History Of Medieval Philosophy, F. C. Copleston, Harper & Row, 1972, p. 50).

Alexandria and Athens would lose their position as pagan centers of learning during Late Antiquity. The remains of the Library of Alexandria (Serapeum) were destroyed by Patriarch Theophilus of Alexandria in 391 CE. The struggle for power between the Roman prefect Orestes (fl. 415 CE) and Patriarch Cyril of Alexandria (ca. 376-444 CE) would lead to the murder of the pagan philosopher Hypatia Hypatia (ca. 350-370-415 CE). In March 415 CE Hypatia was murdered by Christians, which marked the downfall of Alexandrian intellectual life. In 529 CE Roman Emperor Justinian I (ca. 482-565 CE) closed the Platonic Academy and thereby ended the classical period of philosophy in Western Europe. The wisdom of the Greeks would continue in the Academy of Edessa in Syria. Greek philosophy would also continue to exist in the Muslim world (Aristotle) and the Byzantine Empire (Platonism) before it was revived in Western Europe during the Italian Renaissance (Neoplatonism). In the Imperial Library of Constantinople many classical works would be preserved during the Byzantine Empire.

The Hermetic and Gnostic tradition of Neoplatonism would have a profound influence on the revival of Platonism during the Renaissance, mainly due to the works on Plato of Marsilio Ficino (1433-1499 CE), Giovanni Pico della Mirandola (1463-1494 CE) and other members of the Florentine Academy.

The philosophy of Aristotle (384-322 BCE) developed into the Peripatetic school, which was lead by a Scholarch. During the imperial period members of the school concentrated on preserving and commentating on Aristotle's works, rather than extending them. Andronicus of Rhodes (fl. ca. 60 BCE) compiled a collection of Aristotle's 'esoteric' writings, which would become the basis for the Corpus Aristotelicum. Boethus of Sidon (ca. 75-ca. 10 BCE) wrote commentaries (hupomnemata) on Aristotle which are lost. Alexander of Aphrodisias was the most important commentator of Aristotle in the Roman era. He would share the title of 'the commentator' with Averroes (Ibn Rushd) (1126-1198 CE).

European Classical Philosophy studies the philosophical activities and enquiries of the Greco-Roman thinkers.

From the 4^th century BCE to the rise of Christian philosophy in the 4^th century CE, Epicureanism, Stoicism, Skepticism and Neoplatonism were the main philosophical schools in the Western European world. Roman philosophy is mainly grounded in the traditions of Greek philosophy. A thorough study of Greek philosophy was first introduced in the Roman Republic at the time of Marcus Tullius Cicero (106-43 BCE) and Marcus Terentius Varro (116-27 BCE). Cicero chiefly took it up in a spirit of eclecticism ; but among his contemporaries Epicureanism is represented in the poetical treatise of Titus Lucretius Carus (ca. 99-55 BCE) De rerum natura (DRN, E: on the nature of things), and Pythagoreanism by Publius Nigidius Figulus (ca. 98-45 BCE). In De rerum natura Lucretius stated that only two realities exist, solid, everlasting particles (atoms) and the void. Lucretius put forward a universal causal explanation based on the invisible "generative particles" or "seeds", which lead to elimination of the threats the world seems to pose, a vindication of free will, and disproof of the soul's survival after death. Lucretius put forward that man should study science in order to rid yourself of unneccesary fears, especially of the gods and death. Sensation is the basis of all knowledge. Pleasure that leads to pain should be avoided and pain that leads to pleasure should not be avoided. Pleasure means freedom from pain in the body and trouble in the mind. Not all desires are to be satisfied. Most pleasure is to be obtained by living a simple life. In Roman Imperial times Epicureanism and Stoicism were most popular, especially the latter, as represented by the writings of Lucius Annaeus Seneca (Seneca the Younger) (ca. 4 BC-65 CE), Lucius Annaeus Cornutus (ca. 60 CE), and the emperor Marcus Aurelius (121-180 CE); while Eclectic (Middle) Platonism was taken up by Lucius Apuleius (ca. 125-180 CE), who wrote the Metamorphoses, otherwise known as The Golden Asse.

Justin Martyr (100-ca. 165 CE) was an early Christian philosopher who wrote on the doctrine of the Logos and argued that many Stoic and Platonic philosophical ideas were similar to ideas revealed in the Old Testament. His writings represent the first positive encounter of Christian revelation with Greek philosophy. For Justin Martyr the highest aspiration of both Christianity and Platonic philosophy is a transcendent and unchangeable God; consequently, an intellectual articulation of the Christian faith would demonstrate its harmony with reason. One of the main challenges for Christian philosophers was to answer the question "what Athens (philosophy) has to do with Jerusalem (faith)"? For Tertullian (ca. 160-ca. 225 CE) the scriptures would provide all the knowledge necessary both for salvation and for ordinary understanding. Anything the world can offer is either better said in the scriptures, or not worth saying at all. In Liber De Praescriptione Haereticorum (On the prescription of heretics) Tertullian deals with how to think about heresy and how to argue with heretics (or not). The logic of Tertullian is that Christ received the truth from God and transmitted it to his apostles; they in turn handed it on to the churches they founded; outside this Apostolic chain, no one can possess the truth. In chapter 7 of this work Tertullian puts forward 'What has Athens to do with Jerusalem?', meaning that philosophical methods of enquiry have nothing to do with the teaching by authority of the scripture. Clement of Alexandria (ca. 150-ca. 215 CE) on the other hand held that wisdom is to be found in secular sources as well as in the scriptures (e.g. Proverbs 4:8-9, Galatians 3:24). Philosophy was being regarded as a preparation, paving the way for him who is perfected in Christ. Origen of Alexandria (184/185-253/254 CE) identified Platonism as having arrived by reason at the truths of the gospel. For Origen the Platonists had understood the nature of God and his relation to man and the world. Ultimately, it was Origen's path of synthesis that won out in the Christian tradition. It was (Neo)Platonism that would become the fundamental theory on which Christian theology was grounded.

Late antiquity was the period in history from the end of the Roman Empire's Crisis of the Third Century (ca. 235-284 CE) to the re-organization of the Eastern Roman Empire under Heraclius (ca. 575-641 CE) and the Muslim conquests in the mid-7^th century. In late antiquity, Christianity would gain a profound influence on the philosophical development of Europe. Christian philosophers would reject several aspects of ancient philosophy, such as the materialism of Epicureanism and the immanent pantheism of Stoicism. The philosophies of Plato and Aristotle which postulated a transcendent reality (the Ideas of Plato and the Unmoved Mover and Forms of Aristotle) would provide Christianity with a philosophical basis upon which it would develop its theology.

Augustinus of Hippo (354-430 CE) stood in the Neoplatonic tradition of philosophy and provided Christianity with a Platonic foundation. He believed that the grace of Christ was indispensable to human freedom, and he framed the concepts of original sin and just war. His most important works are his Confessiones, De Civitate Dei contra Paganos, and Enchiridion. He is the first Western philosopher to promote what has come to be called "the argument by analogy" against solipsism. In his Confessiones Augustinus of Hippo puts forward the Harmony of Faith and Reason, but comes to the conclusion that philosophy is inferior to faith. The classical role of philosophy comes to an end and is being replaced by faith and theology. Augustine tried to reconcile his beliefs about free will, especially the belief that humans are morally responsible for their actions, with his belief that one's life is predestined. In De doctrina christiana (397-426 CE) he provided the rules for the interpretation of Scripture (hermeneutics), and made the distinction between "veritas connexorum" (linked truisms) and "veritas sententiae" (truth defined, using natural philosophy to understand creation and theology, the "Book of Nature"). Augustinus of Hippo made the link between natural philosophy (science) and theology which would develop into the Medieval synthesis between natural philosophy and theology
(see also Church Fathers: From Clement of Rome to Augustine : General Audiences, 7 March 2007-27 February 2008, Pope Benedict XVI, Ignatius Press, 2008, p. 181 and Teaching the Tradition: Catholic Themes in Academic Disciplines, John J. Piderit, Melanie M. Morey, Oxford University Press, 2012, p. 67).

Martianus Capella (fl. 410-420 CE) was one of the earliest developers of the system of the seven liberal arts that structured early medieval education. In De nuptiis philologiae, et Mercurii, et de septem artibus liberalibus libri novem ("On the Marriage of Philology and Mercury") relates the courtship and wedding of Mercury (intelligent or profitable pursuit) with the maiden Philologia (learning, or more literally the love of letters and study). Among the wedding gifts are seven maids who will be Philology's servants: they are the seven liberal arts. In the story lady Geometry is the most learned and of all Philology's seven bridesmaids, which emphasizes the importance of geometry in the arts during antiquity
(see also Martianus Capella and the Seven Liberal Arts: The Marriage of Philology and Mercury, William Harris Stahl, Richard Johnson, E. L. Burge, Columbia University Press, 1992).

One of the latest philosophical writers of antiquity is Anicius Manlius Severinus Boethius (ca. 480-524 or 525 CE) who wrote his Consolatio Philosophiae (524) while in prison, and whose writings were the chief source of information as to Greek philosophy during the first centuries of the Middle Ages (mainly Aristotelianism, concept of Fortune). Boethius drew extensively on the thinking of Greek Neoplatonists such as Porphyry (234-ca. 305 CE) and Iamblichus (ca. 245-ca. 325 CE). His completed translations of Aristotle's works on logic, De topicis differentiis were the only significant portions of Aristotle available in Western Europe until the 12^th century. In De syllogismis categoricis (On categorical syllogisms), Boethius gives an explanation of the basic element of the Aristotlian syllogism, i.e., propositio, and of the syllogism. In his book De Institutione Musica he wrote on the fourfold classification and meaning of music: musica universalis (musica mundana, Pythagorean harmony of the spheres, macrocosm), musica humana (harmony of human body and spiritual harmony, microcosm), musica instrumentalis (voices and instruments) and Musica divina (music of the Gods). Together with Augustinus of Hippo (354-430 CE) and Aristotle (384-322 BCE), Boethius was the fundamental philosophical and theological author in the Western Latin tradition during the Middle Ages. Lorenzo Valla (1407-1457 CE) described Boethius as the last of the Romans and the first of the scholastic philosophers.

Flavius Magnus Aurelius Cassiodorus Senator (ca. 485-ca. 585 CE) in his Institutiones Divinarum et Saecularium Litterarum (543-555 CE) (Book I and Book II) would provide several competing definitions of philosophy, such as "Philosophia est divinarum humanarum que rerum, in quantum homini possibile est, probabilis scientia", "Aliter, philosophia est ars artium et disciplina disciplinarum" and "Rursus, philosophia est meditatio mortis: quod magis convenit Christianis". In his Institutiones Divinarum et Saecularium Litterarum Cassiodorus put forward that the aim of cognition should be the divine wisdom contained in the Holy Bible. He made the study of the liberal arts (litterae saeculares), an introduction to the science of theology (litterae divinae). In the liberal arts he distinguished the mutually complementary artes (arts) of the trivium and the disciplinae (sciences) of the quadrivium. In the arts of the Trivium he listed grammar, rhetoric, and dialectic. Among the sciences of the Quadrivium he listed arithmetic, music, geometry, and astronomy. Art (ars) is an ability to produce contingent things that could be otherwise ("artem esse habitudinem operatricem contingentium, quae se aliter habere possunt"), hence the object and rules of art are variable and depend upon the subject with regard to the choice of object and the modes of operation. Science is concerned with things that could not be otherwise ("disciplina vero est quae de his agit, quae aliter evenire non possunt"), and so the object and rules of science are stable and the subject who practices science cannot change anything in the object and rules of science. In science the intellect takes a theoretical attitude (a purely cognitive attitude), as opposed to the active attitude in arts. The distinction between artes and disciplinae in the liberal arts, rooted in the division between the Greek τεξηναι (E: technai) and επιστεμαι (E: epistemai) marked the foundations of the division into the trivium and quadrivium, where the trivium was a necessary preparation for the quadrivium. The arts were divided into three humanistic arts called the trivium, the artes liberales triviales (artes rationales, sermocinales), and the four natural arts called the quadrivium, the artes liberales quadriviales (artes reales).

Scuola di Atene by Raphael in the Vatican Stanza della Segnatura

Greek Philosophy
Ancient Greek Philosophy
Early Greek Philosophy
Ellopos
Hellenistic civilization
Roman Philosophy
The Latin Library
Epicurus & Epicurean Philosophy
Stoicism
Ancient Skepticism
Skepticism
Cosmos of the Ancients
The Seven Sages of Greece
Classic Rhetoric & Persuasion
Encyclopaedia Romana
The Lives and Opinions of Eminent Philosophers - Diogenes Laertius

Pneumatology
Nous
Arche
Logos - Wikipedia
Logos
Harmonia

Pherecydes of Syros - pentemychos, "immortality of the soul" (6th C. BCE)
Life of Pherecydes - Diogenes Laertius
Thales of Miletus - (ca. 620 BC-546 BCE)
Thales of Miletus - (ca. 620 BC-546 BCE)
Pythagoras - (ca.580-500 BCE)
The Complete Pythagoras
Heraclitus - (ca. 6th Century BCE)
Heraclitus on the Logos - by Gordon L. Ziniewicz
Parmenides of Elea - (early 5th century BCE) "Monism"
Empedocles - (ca. 495-435 BCE) "four material elements" & "two opposing forces"
Love and Strive - Empedocles
Protagoras - (ca. 490-ca. 420 BCE)
Socrates - (ca.469-399 BCE)
Socrates - (ca.469-399 BCE)
The Socratic Method
Plato - (ca.427-347 BCE)
Plato and his dialogues - Plato
Timaeus - Plato
Timaeus - Plato
Aristotle - (384-322 BCE)
Complete works of Aristotle - Aristotle
Metaphysics - Aristotle
Aristotle and Aristotelianism - Aristotle
Pyrrho of Elis - (ca.360 BCE-ca. 270 BCE)
Epicurus - (341-270 BCE)
Epicurean paradox
Zeno of Citium - (333 BCE-264 BCE)
Marcus Tullius Cicero - (c. 106-43 BCE)
Epictetus - (ca.55-ca.135 CE)
Discourses - Epictetus
Enchiridion - Epictetus
Marcus Aurelius (121-180 CE)
The Meditations - Marcus Aurelius (167 CE)
Hypathia of Alexandria - (c. 370-415 CE)
The Life and Death of Hypathia of Alexandria
Simplicius of Cilicia - (490-560 CE)
Johannes Philoponus - (ca 490-ca 570 CE)
Anicius Manlius Severinus Boethius - (480-524 or 525 CE)
Consolatio Philosophiae - Boethius

The Mysterious Fate of the Great Library of Alexandria
The end of the Academy - Justinian (529 CE)
The end of Antiquity

The Middle Ages of Western Europe are commonly dated from the 5^th century fall of the Western Roman Empire and the barbarian invasions until the Fall of Constantinople on 29 May 1453 CE or the 16^th century Western Schism and the dispersal of Europeans worldwide at the start of the European overseas exploration. The end of the Western Roman Empire and the beginning of the Middle Ages were initiated when the Roman Emperor Romulus Augustulus was forced to abdicate by Flavius Odoacer (433-493 CE) on 4 September 476 CE. The Eastern Roman (Byzantine) Empire would continue to exist until the Fall of Constantinople on 29 May 1453 CE. Several Greek and non-Greek intellectuals fled Constantinople before and after the siege, migrating particularly to Italy, where they helped fuel the Renaissance. The most important contributions to Medieval Philosophy during the Early Middle Ages were made by Early Islamic and Byzantine philosophers.

In the Early Islamic thought, two main currents may be distinguished. The first is Kalam, that mainly dealt with theological questions and the other is Falsafa, that was founded on the reception of Greek thought. The period of Classical Islamic philosophy is a period of intense philosophical development beginning in the early 9^th century CE and lasting until the late 12^th century CE. The period in history is known as the Islamic Golden Age, and the achievements of this period had a crucial influence in the development of modern Western philosophy and science. This period started with al-Kindi (ca. 800-870 CE) in the 9^th century and ends with Abū 'l-Walīd Muḥammad ibn Aḥmad ibn Rushd (Averroes) (1126-1198 CE) at the end of 12^th century. The Sufi mystic Shahab al-Din Suhrawardi (1155-1191 CE) developed Illuminationism (hikmat al-ishraq), a combination of Avicennism and ancient Persian philosophy, along with many new innovative ideas of his own. Some scholars consider the era of Averroes (1126-1198 CE) the era of rational scientific enlightenment in Islam
(see also A History of Islamic Philosophy, Majid Fakhry, Columbia University Press, 2004 and What is Islamic Philosophy?, Roy Jackson, Routledge, 2014 and Averroës and the Enlightenment, Murād Wahbah, Prometheus Books, 1996 and Islamic Enlightenment and the Paradox of Averroes., Stefan Wild, Die Welt Des Islams 36, no. 3 (1996): pp; 379-90).

Abu Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (Al-Kindi) (ca. 801-873 CE) was the first philosopher as such in the Islamic world. He is considered the father of Islamic philosophy and participated in the translation of Aristotle, the Neoplatonists, and Greek mathematicians and scientists into Arabic. Al-Kindi wrote the Theology of Aristotle and Book of Causes based on Plotinus and Proclus. Al-Kindi was mainly influenced by Aristotle and also by Neoplatonism. His best known treatise is the Fi al-Falsafa al-Ula (On First Philosophy). In this treatise, influenced by Aristotle, he described the first philosophy, which is also the most noble and highest philosophy, as the knowledge of the first truth, including the cause of every truth (the first cause). The first cause is prior in time because it is the cause of time. By the study of philosophy, people will learn the knowledge of things in reality, and through this the knowledge of the divinity of God and his unity. This way they will also learn human virtue. He also emphasized the importance of the intellect ('aql) and contrasts it with matter. For Al-Kindi the One Truth is another name for God, and it does not have any attributes, predicates or characteristics. He also discussed the absolute unity of God, his power as creator of the world creation ex nihilo and of creation. Here he did not agree with Aristotle, who postulated the eternity of the world. The Eternal (God) is not due to another and has no cause and has neither genus nor species. There is no 'before' for the Eternal as it is infinite outside the bounds of time. The Eternal is unchanging, immutable and imperishable. For humanity, death is the soul's taking leave of the body, which it employed during life. For al-Kindi, the intellect continues after death and the soul is considered primarily the locus of the intellect. On ethics he wrote a treatise Fi al-hila li-daf‘ al-ahzan (On the Art of Averting Sorrows) which was influenced by Stoicism. Like in Stoicism Al-Kindi emphasizes to concentrate on the life of the mind and the soul, not of the body. With al-Kindi, who pursued reason against the background of revealed religion, begins the Islamic Golden Age which continued with the works of Ibn Sina (Avicenna) (ca. 980-1037 CE) and Ibn Rushd (Averroes) (1126-1198 CE)
(see also Al-Kindi, Peter Adamson, Oxford University Press, 2006 and The Philosophical Works of al-Kindi, Peter E. Pormann, Peter Adamson, OUP Pakistan, 2012 and Al-Kindi's Metaphysics: On First Philosophy' Fi al-Falasafah, Alfred I Ivry (intro.), SUNY, 1974)

In the ninth century, Plotinus (204/5-270 CE) was translated into Arabic, which would bring the Arabic world into contact with Neoplatonism. Long sections of this translation became known as the Theology of Aristotle, which was derived from the Enneads. Ali al-Husayn ibn Sina (Avicenna) (ca. 980-1037 CE) was the most important philosopher of the Eastern (Persian) region of Islam. He tried to redefine the course of Islamic philosophy and channel it into new directions, and particularly to reconcile Aristotelianism and Neoplatonism with Islamic theology. He created a new synthesis, most evident in his broadly influential teachings on Allah as the Necessary Being and the human soul's separability from the body. His most important works are the Kitab al-Shifa' (E: Book of the Cure) and the Al-Qanun fi al-Tibb (E: The Canon of Medicine). He wrote the Kitab al-Shifa', modelled on Aristotle and in this work he covers the natural sciences, logic, mathematics, metaphysics and theology. In the Kitab al-Shifa' he put forward his doctrines on the nature of the soul and his famous existence-essence distinction, which would have a profound influence on Scholasticism. Avicenna put forward the existence of a single, shared agent intellect for all human beings. Avicenna also developed his own system of Logic, known as Avicennian Logic, as an alternative to Aristotelian Logic, and by the 12^th Century it had replaced Aristotelian Logic as the dominant system of Logic in the Islamic world. Avicennian Logic had an influence on early medieval European logicians such as Albertus Magnus (1193/1206-1280 CE), although Aristotelian Logic later became popular in Europe due to the strong influence of Averroism. Avicenna developed an early theory of the hypothetical syllogism as well as propositional calculus, an area of logic not covered in the Aristotelian tradition. He also contributed inventively to the development of inductive logic, mainly through his medical writings such as Al-Qanun fi al-Tibb (E: The Canon of Medicine) (1025 CE). In Epistemology and the theory of knowledge, Avicenna developed the concepts of empiricism and the tabula rasa (the idea that individual human beings are born with no innate or built-in mental content). Avicenna was also the first to describe the methods of agreement, difference and concomitant variation which are critical to inductive logic and the scientific method, which was essential to later scientific methodology. Avicenna also developed the idea of the first (intentio prima) and second intention (intentio secunda) in logic
(see also Dictionary of Islam, Thomas Patrick Hughes, Asian Educational Services, 2001, p. 455 and The Terms "Prima Intentio" and "Secunda Intentio" in Arabic Logic, Kwame Gyekye, Speculum Vol. 46, No. 1 (Jan., 1971), pp. 32-38). Medieval philosophers use "intention" as synonymous with "concept", so that the answer that a philosopher gives to the question of an intention's ontological status follows from his resolution of the nature of a concept. The distinction between first and second intentions traces back to Avicenna, who speaks of logic as a science dealing with second intentions as applied to first intentions. Roughly speaking, first intentions are concepts of extramental things (for example, man), while second intentions are concepts of concepts (for example, species)
(see also The Cambridge History of Later Medieval Philosophy: From the Rediscovery of Aristotle to the Disintegration of Scholasticism, 1100-1600, Norman Kretzmann (Editor), Anthony Kenny (Editor), Jan Pinborg (Editor), Eleonore Stump (Editor), Cambridge University Press, 1982, p. 492).

Avicenna's arguments for the Necessary Being (wajib al-wujud bi-dhatihi) would appear in a number of his works. In the Metaphysics of his Kitab al-Shifa' (I, 5), the argument that leads to the Necessary Being is on being (mawjud) and thing (shay'). In the Metaphysics, Avicenna puts forward that there are three first intentions that arise initially in the soul: being or existent, thing, and necessary. These are primary intentions that naturally arise as first principles grasped by the mind in the consideration of reality in any of its forms. But apprehended 'essentia' has of its very nature an indeterminate openness to various sorts of existence (Wujud) determined by something outside the essence (Mahiat). The arguments for the existence of the Necessary Being then proceed by rejection of the impossibility that all beings are merely possible or contingent and the acceptance that there must be necessary being for the actual existence. Since there cannot be an infinite regress of beings necessary by another, Avicenna concludes that there must be a first, the unique Necessary Being that causes the existence of the dependent necessary and possible beings and is itself uncaused (e.g. Aristotle's 'Primum Movens'). This analysis leads to the Avicennian distinction of essence and existence so influential in Arabic philosophy and in the Latin West. For Aristotle essence (Form, ousea) and existence (e.g. body) were closely intertwined (hylomorphism), but Avicenna would separate them. The First is the True One that is existence alone, free of the limitation of form, while all other things are form and being received ultimately from Allah. Causality here is by way of emanation, as with Abu Nasr al-Farabi (ca. 870-950 CE), in a hierarchy of necessary beings, except that for Avicenna there is an emanation of an intellect, a celestial sphere, and a celestial soul associated with the celestial intellect as its mover. Holding firm to the principle "from one only one can arise", Avicenna asserted that there first was emanated an intellect and from that plurality arose. This emanation continues down to the level of the moon, at which point the agent intellect generated the sublunar world and all the forms in it.

This agent intellect is denominated the 'giver of forms' because it gives forms both to human minds and to natural entities of the world. The human soul has a temporal origination and its individuation in being is the result of its association and joining with the body. But its nature as intellectual shows that it is not merely the form of a body. Rather, its nature as rational indicated to Avicenna that the soul is incorruptible and that it does not die with the death of the body. This is illustrated (not proved) by the famous "Flying Man" argument which holds that it can be imagined that even if a man is suspended in the air and in complete sensory deprivation as if bodiless, he would nonetheless affirm his existence as a rational soul. According to his Letter to Kiya (1036 CE), a letter that Avicenna wrote to a disciple, the key principle is found in Aristotle's discussion of the atomism of Democritus (ca. 460-370 BCE) in De Anima and the notion that intelligibles can only exist in immaterial subjects. The common explanation is that these intelligibles come to be in the soul by emanation when the soul is prepared for their reception and not by true abstraction. For Avicenna the soul of a prophet, such as Muhammad (ca. 570-632 CE), has special powers of imagination to receive intelligibles directly from the agent intellect and to communicate them to the people in religious discourse. Avicennism would have a profound influence on the development of European philosophy and theology, such as with William of Auvergne (ca.1180/90-1249 CE), Albertus Magnus (1193/1206-1280 CE), and Thomas Aquinas (1225-1274 CE).

Averroes criticized Avicenna, mainly due to his divergence from Aristotle. In particular, he rejected the theory of the celestial Souls and of an imagination which is independent of the corporeal senses. Averroes wrote The Incoherence of the Incoherence (1126-1198 CE) as a defence of the use of Aristotelian philosophy within Islamic thought. It was a response to The Incoherence of the Philosophers of Al-Ghazali (1058-1111 CE) who had criticized the Avicennian school of early Islamic philosophy. In The Decisive Treatise Determining The Connection Between The Law And Wisdom Averroes stresses the importance of analytical thinking as a prerequisite to interpret the Holy Qur'an. In The Decisive Treatise, he set forth what may be termed a kind of fatwa or formal legal and religious opinion reasoning subtly for the priority of philosophy to revelation in the determination of truth. Averroes makes two important identifications:

• The religious reflection commanded by the Holy Qur'an he identifies with the theoretical sciences.
• The traditional Islamic reasoning by analogy he identifies with syllogistic logic called by the same name.

Averroes wrote the famous Long Commentaries on the works of Aristotle, which contain the complete text of Aristotle with Averroes' section-by-section commentary drawing on the work of key figures of the Greek and Arabic traditions. In his work he used the classical commentators Themistius (317-ca. 390 CE) and Alexander of Aphrodisias ( fl. 200 CE) and the falasifah (Muslim philosophers) al-Farabi (ca.870-950 CE), Avicenna (ca. 980-1037 CE), and his own countryman Avempace (Ibn Bajjah). In his Long Commentary on the Metaphysics of Aristotle Averroes asserted that the most noble of all worship of God consists not in religious practices but in the intellectual apprehension of God and creation in the philosophical science of metaphysics. In his Commentaries on Aristotle Averroes put foward important Aristotelian viewpoints on the eternity of the world, the denial of the immortality of the individual human soul and the contention that ultimate human happiness is something had only in mortal earthly existence. Averroes would develop the doctrine on the material intellect, which states that the human mind is a composite of the material intellect and the passive intellect. Averroes' Long Commentary on Aristotle's De Anima would play an important role in the Medieval debate on the human soul. Aristotle in De Anima (Ch. V) had argued that the mind (only the agent intellect) is immaterial, able to exist without the body, and immortal. Averroes in his understanding of universals came to the conclusion that there is only one 'intellectus universalis'(E: intellectual soul; material intellect, passive intellect) common to the whole human race; but individually men have their own sensitive spirit or 'intellectus sensitivus' (active intellect) which gives them "personality". There must be one commonly shared collection of intelligibles to which different human beings refer in language and knowledge. The agent intellect must be in the soul. Those intelligibles in act are to be found in the immaterially separate yet shared material intellect. The agent intellect acts upon images that contain intelligibles in potency from human experiences of the world through the five external senses and the four internal sense powers (common sense, imagination, cogitation and memory). These images are denuded as much as possible from accidents and materiality and abstracted and separated from particularity by the intellectual activity of the separately existing agent intellect. Those separated intelligibles, now existing as intelligibles in act, are in the same instant impressed upon the unique receptive incorporeal material intellect which functions to satisfy the requirement of intelligibles in act for an immaterial and singular subject (universal). The death of Averroes effectively marks the end of a particular discipline of Islamic philosophy usually called the Peripatetic Arabic School (Aristotelianism). Averroes however would have a profound influence on Western philosophy, although his doctrine on the unity of the material intellect would become controversial. Later Thomas Aquinas (1225-1274 CE) would respond to Siger of Brabant (ca. 1240-1280 CE) and others of Averroist leanings at the University of Paris in his De unitate intellectus contra Averroistas (1270 CE). At the University of Paris, Aristotle would be 'tamed' and made acceptable for the Western Christian tradition and its intepretation of Scripture.

After Averroes philosophical activity declined significantly in Western Islamic countries, namely in Islamic Spain and North Africa, though it persisted for much longer in the Eastern countries, in particular Persia and India where several Islamic schools of philosophy continued to flourish, such as Avicennism, Illuminationist philosophy, Mystical philosophy, and Transcendent theosophy. Al-Ghazali (1058-1111 CE), Fakhr al-Din al-Razi (1149-1209 CE) and the Ash'ari theologians objected to Avicennism mainly on the grounds of its inconsistencies with the Qur'an and Hadith. Al-Ghazali's famous work The Incoherence of the Philosophers was specifically aimed at Avicenna.

The Byzantine philosophy of the Middle Ages refers to the distinctive philosophical ideas of the philosophers and scholars of the Byzantine Empire, especially between the 8^th and 15^th centuries CE. Their philosophy was characterised by a Christian world-view, but one which could draw ideas directly from the Greek texts of Plato, Aristotle, and the Neoplatonists. Byzantine scholars throughout the Medieval period had the Imperial Library of Constantinople at their disposal.
Greek science and literature remained alive in the Byzantine world while it declined in the West, and like the Islamic philosophy of the time the Byzantine philosophy drew heavily on Plato, Aristotle, and the Neoplatonists, even if it was now Christian in tone. In the 7^th century CE, the Syrian monk John of Damascus or Iohannes Damascenus (ca. 676-4 December 749 CE) produced a three-part encyclopedia Fountain of Knowledge or The Fountain of Wisdom containing in its third part An Exact Exposition of the Orthodox Faith (Ekdosis akribes tes orthodoxou pisteos) a systematic exposition of Christian theology. In the 9^th century Photios I (ca. 810-ca. 893 CE) the Ecumenical Patriarch of Constantinople (858 to 867 and from 877 to 886 CE), the Patriarch of Constantinople, collected many works by ancient writers, and studied Aristotelian logic, and his pupil Arethas of Caesarea (born ca. 860 CE), Archbishop of Caesarea early in the 10^th century, commentated on works by Plato and Aristotle (Commentaria in Aristotelem Graeca). By the 11^th and 12^th centuries there was a growing interest in the teaching of philosophy, and we have figures such as Michael Psellos (ca. 1018-ca. 1078 CE), Eustratius of Nicaea (ca. 1050/1060-ca. 1120 CE) Metropolitan bishop of Nicaea, and Michael of Ephesus (early or mid-12^th century CE) who all wrote commentaries on Aristotle. Michael of Ephesus wrote the first full commentary on the Sophistical Refutations. In the 13^th and 14^th centuries CE we have important philosophers such as Nicephorus Blemmydes (1197-1272 CE) and Theodore Metochites (1270-1332 CE). An important figure was Gregory Palamas (1296-1359 CE), a monk of Mount Athos, who developed a mystical movement known as Hesychasm, which involved the use of the noetic Jesus prayer to achieve a vision of the uncreated Light also called the Illumination or Vision of God (Orthodoxy teaches of two cognitive faculties, the nous and logos). Based on Christ's injunction in the Gospel of Matthew "et cum oratis non eritis sicut hypocritae qui amant in synagogis et in angulis platearum stantes orare ut videantur ab hominibus amen dico vobis receperunt mercedem suam tu autem cum orabis intra in cubiculum tuum et cluso ostio tuo ora Patrem tuum in abscondito et Pater tuus qui videt in abscondito reddet tibi" (Vulgata, Matthew 6:5-6) (E summarized: go into your closet to pray), hesychasm in tradition has been the process of retiring inward by ceasing to register the senses, in order to achieve an experiential knowledge of God.

It was the Hesychast, Eastern Orthodox Church's mystical teaching on prayer, movement which caused a riff in the Christian East which lead many philosophically minded individuals to go to Western Europe. Especially the role of Barlaam of Calabria (ca. 1290-1348 CE), who opposed Hesychasm, played a role in the formation of Roman Catholic theology in Western Europe. The migration of Byzantine scholars and other émigrés from southern Italy and Byzantium during the decline of the Byzantine Empire (1203-1453 CE) and mainly after the fall of Constantinople in 1453 CE until the 16^th century, is considered by some scholars as key to the revival of Greek and Roman studies and subsequently in the development of the Renaissance humanism and science.

The last great philosopher of Byzantium was Georgius Gemistus or Plethon (ca. 1355-1452/1454 CE) who felt that a restored Platonism could reverse the decline of Byzantium. He was an important figure in the transmission of ancient Greek philosophy (Neoplatonism and Hermeticism) to Western Europe. Plethon re-introduced Plato's thoughts to Western Europe during the 1438-1439 Council of Florence (1438-1439 CE), a failed attempt to reconcile the East-West schism of the Byzantine and Roman church. During the council, at the invitation of some Florentine humanists, he set up a temporary school to lecture on the difference between Plato and Aristotle. He summarized the difference between Plato and Aristotle's conceptions of God in his De Differentiis in order to show that the concept of Plato was closer to Christianity. Plethon's work the Nomoi (Summary of the Doctrines of Zoroaster and Plato) which was inspired by the Laws (Nomoi) of Plato, contains the constitution for a Platonic city-state. Plethon drew up plans in his Nomoi to radically change the structure and philosophy of the Byzantine Empire in line with his interpretation of Platonism. Plethon with his lectures inspired Cosimo de' Medici (1389-1464 CE) to found the Accademia Platonica or "Florentine Academy".

The Medieval philosophy of Western Europe spans the period between the decline of classical pagan culture and the rise of the Renaissance. It combines classical pagan philosophy, basically Greek but mainly in its Roman versions, with the new Christian religion. During the Early Middle Ages Plato (424/423-348/347 BCE) would play an important role in Western philosophy, while during the High Middle Ages, after the 12^th century, Aristotle (384-322 BCE) would play an important role in the development of Scholasticism. An important difference between classical (pagan, Indo-European culture) and Medieval Western philosophy was that Christianity (Scripture, Church, Abrahamic or Semitic culture, revealed religion) became part of the empirical environment of philosophy. The Middle Ages would start Neoplatonic, then proceed into Neo-Aristotelianism. The rise of the Renasissace would witness the rediscovery of Plato and a new interpretation of Aristotle. The confrontation of pagan Greek (Indo-European) philosophy with the requirements of the Abrahamic (Semitic) monotheism of Christianity, would require a new synthesis between philosophy and religion. The Latin synthesis of Greek philosophy and Christianity can be summarized in the Scholastic table of transcendentals (ens, res, unum, aliquid, verum, bonum) or "ens et unum, verum, bonum, pulchrum convertuntur", meaning that for instance the Greek philosophical truth (verum) and the Christian good (bonum) are interchangeable as they are ontologically one. The Christian God united whithin himself Truth, Goodness, and Beauty, thereby connecting the cosmological logos with goodness
(see also Early Medieval Philosophy 480-1150: An Introduction, John Marenbon, Routledge, 2002 and Qu'est-ce que la philosophie au Moyen Âge?, Jan Aertsen, Andreas Speer, Walter de Gruyter, 1998, p. 675 and Structure and Being: A Theoretical Framework for a Systematic Philosophy, Lorenz B. Puntel, Penn State Press, 2010, p. 440 and L'être et la beauté chez Jacques Maritain, Volume 90, Raoul Gross, Saint-Paul, 2001, p. 100).

During the Early Middle Ages Neoplatonism had a profound influence on Western philosophy. In De Doctrina Christiana (started 396, completed 426), Aurelius Augustinus or Augustine (354-430 CE) explained how classical education fits into the Christian worldview. For Augustine Christianity was a religion of the book, so Christians must be literate. Tertullian (ca. 160-ca. 225 CE) had been more sceptical of the value of classical learning, but even he did not object to Christian enrollment in classical schools. Anicius Manlius Severinus Boethius (ca. 480-524 or 525 CE) translated some works of Aristotle and Nicomachus of Gerasa (ca. 60-ca. 120 CE) into Latin. Simplicius of Cilicia (ca. 490-ca. 560 CE) was one of the last of the Neoplatonists and wrote extensive commentaries on the works of Aristotle (384-322 BCE) such as De Caelo, Physica Auscultatio, Categories, De Anima and the Enchiridion of the Stoic philosopher Epictetus (ca.55-ca.135 CE). For Simplicius of Cilicia, and most commentators of Aristotle of the early medieval or late antique period, their Platonism was so comprehensive as a system of thought that it could harbor Aristotle's philosophy. Their major exegetical concern became that of finding substantial agreement between Plato and Aristotle. For most of these commentators, the disagreement on specific issues between Aristotle and Plato did not preclude harmony between the two philosophers on a deeper level. Within this tradition the Categories of Aristotle was considered an elementary introduction to the whole of philosophy and as such it was used to teach beginners with little or no knowledge of philosophy
(see also Early Medieval Philosophy 480-1150: An Introduction, John Marenbon, Routledge, 2002, p. 10 and Medieval Philosophy: From 500 to 1500 CE, Brian Duignan, The Rosen Publishing Group, 2011, p. 12).

John Scottus Eriugena (ca. 800-ca.877 CE) tried to create a consistent, systematic, Christian Neoplatonism. He was one of the leading philosophers of the Carolingian Renaissance. In his Periphyseon, Eriugena developed a Neoplatonic cosmology according to which the infinite, transcendent and 'unknown' God, who is beyond being and non-being, through a process of self-articulation, procession, or 'self-creatio', proceeds from his divine 'darkness' or 'non-being' into the light of being, speaking the Word (logos) who is understood as Christ, and at the same timeless moment bringing forth the Primary Causes of all creation. John Scottus Eriugena defines Nature as 'universitas rerum', the 'totality of all things', and includes both the things which are (ea quae sunt) as well as those which are not (ea quae non sunt). The identity of God and creation in the Periphyseon or De Divisione Naturae and the principle of double predestination in De Divina Praedestinatione were condemned in the thirteenth century at the Councils of Valencia (855 CE) and Langres (859 CE). John Scottus Eriugena would influence Christian Neoplatonists such as Meister Eckhart (ca. 1260-ca. 1327 CE) and especially Nicolaus Cusanus (1401-1464 CE)
(see also The Routledge Handbook of Neoplatonism, Svetla Slaveva-Griffin, Pauliina Remes, Routledge, 2014, p. 516).

The philosophical tradition which would grow out of the confrontation of Western European Christianity and ancient Greek philosophy was Latin Scholasticism. Christianity never developed a philosophy of its own, because the teachings left by Jesus of Nazareth and his followers were not suitable to build a consistent and complete philosophical system. Christian scholars trained in Greek philosophy built a philosophical system which attempted to create a synthesis with the biblical texts. Scholasticism was an ardent attempt to harmonize faith and reason, develop Christian philosophy and to reconcile ecclesiastical authority with other avenues of knowledge. Scholasticism thus stems from the assumption that faith is something not only to be believed (credo), but understood (intelligere) as well
(see also Global History of Philosophy: The period of scholasticism, John C. Plott, James Michael Dolin, Russell E. Hatton, Motilal Banarsidass Publ., 1977).

The beginning of scholasticism can be identified in the methods used by civil and canon lawyers of the 11^th and 12^th century to reconcile seemingly contradictory statements between faith and philosophy. The Benedictine Anselm of Canterbury (1033-1109 CE) took as his life's motto "fides quaerens intelligentiam" (E: faith seeking understanding), and sought to use reason to illuminate the content of belief: "Neque enim quaero intelligere ut credam, sed credo ut intelligam. Nam et hoc credo, quia, nisi credidero, non intelligam". Anselm is called the "Father of scholasticism", because of the prominence of reason in his theology. He rejected the anti-intellectual spirit of preceding centuries, and devoted great care to his cultivation of the Augustinian theology of "faith seeking understanding". Rather than establish a position by appeal to authority (argumentum ad verecundiam), he used argument to demonstrate why what he believed on authority must be so. His most important works, written at the monastery of Bec, are the Monologion (1075-76 CE), the Proslogion (1077-78 CE), and his four philosophical dialogues: De Grammatico (1059-60 CE), De Veritate, and De Libertate Arbitrii, and De Casu Diaboli (1080-86 CE). In his later life, his most important work was Cur Deus homo (E: Why God became a man). In De Veritate (E: Of Truth) Anselm stated, in the Aristotelian tradition, that a statement is true "when it signifies that what-is is". Anselm tries to bring unity in the many manifestations of truth. He would add to the Aristotelian concept of "veritas" (truth) also "rectitude" (correctness of judgment). The concept of rectitude is used by Anselm to assimilate all the various manifestations of truth to each other and, in the end, to the Supreme Truth which he identifies with God. Rectitude being the correctness of the sign (symbol, sentence) to the thing it signifies. Rectitude is the real criterion of its epistemological validity. He distinguishes intrinsic "veritas enuntiationis" (natural truth) from "veritas suppositio" (accidental or situational truth). Anselm in De Veritate also argued that all creatures owe their being and value to God as the source of all truth, to whom a life lived well is the highest praise. In the Monologion (1075-76 CE) he argued from the truth of statements to an eternal Supreme Truth and stood in the tradition of Plato and Aristotle with putting forward a First Principle (God as Supreme Truth) from which everything emanates and is connected to. Here he described God as the one most truly good thing (First Principle), from which all real moral values derive and whose existence is required by the reality of those values. Denying the existence of God would lead to (philosophical) contradictions which cannot be solved according to Anselm. In the Proslogion (1077-78 CE) (E: Addition, An address of the soul to God), Anselm proposed his ontological argument, according to which God is understood as "aliquid quod maius non cogitari potest" (E: that than which nothing greater can be conceived). His philosophy would become known as the "Ars Anselmi" or "Regula Anselmi" and Anselm would become one of the "Auctoritas aprobata" of Medieval Scholasticism
(see also The Trouble with Christianity, Philip Voerding, AuthorHouse, 2009, p. 53 and Text-Book of the History of Doctrines, 2 Volumes: In the Ancient Church, and Middle Ages, Early Modern Ages, Reinhold Seeberg, Wipf and Stock Publishers, 1997, p. 56).

The ancient Problem of Universals would be continued in the Medieval Problem of Universals during the Middle Ages. The Neoplatonist Porphyry (ca. 234-305 CE) introduced the problem in his Isagoge or Introduction to Aristotle's Categories. Anicius Manlius Severinus Boethius (ca. 475-526 CE) would translate the Isagoge into Latin which would bring Western Latin scholars into contact with the problem. Realists, following in the tradition of Plato, maintained that each universal is an entity in its own right, existing independently of the individual things that happen to participate in it. Nominalists, on the other hand, pursuing a view nearer that of Aristotle, held that only particular things exist, since the universal is nothing more than a name that applies to certain individual substances. The realist doctrine became known as the via antiqua and the nominalist doctrine as the via moderna. The via moderna is generally associated with the nominalism of William of Ockham (ca. 1287-1347 CE), Jean Buridan (ca. 1300-after 1358 CE), Marsilius of Inghen (ca. 1340-1396 CE), and Gregory of Rimini (ca. 1300-1358 CE), whereas the via antiqua represents the realist positions of Thomas Aquinas (1225-1274 CE) and John Duns Scotus (1265/1266-1308 CE). Petrus Hispanus (fl. 13^th century) wrote the Tractatus or Summulae logicales magistri Petri Hispani on the logica antiquorum and the logica nova. This debate between realists and nominalists on universals was part of the ongoing metaphysical oscillation between a pluralistic world (nominalism, universals as words only, only particulars are real) and a monistic or dualistic view with (transcendent) universals (realism) with a real presence in reality
(see also The Cambridge Companion to Medieval Philosophy, A. S. McGrade, Cambridge University Press, 2003, p. 196).

The most important philosophical problem in the 12^th century was the question of the universal. The medieval problem of universals is a logical, and historical, continuation of the ancient problem generated by Plato's (428-348 BCE) theory of Ideas or Forms. The first medieval nominalist or father of nominalsim, Roscelin (ca. 1050-1125 CE), would be condemned because his nominalism caused problems with regard the the Trinity which had to share one 'essence' and therefore required a realist philosophy in order to support it. Roscelin, because of his nominalism, considered the three Divine Persons as three independent beings (Tritheism). With his nominalism, Roscelin tried to address the problem of fictionalism or the problem of knowing the universals. Plato had put forward his Forms as universals, where they existed outside the chain of causation or causal order but explained its order. Aristotle in his Metaphysics (I, 9) had put forward the dilemma with regard to the Platonic universals: "if the Forms are numbers, how can they be causes". Porphyry would regard universals as 'nuda intellecta' (E: mere abstractions). Roscelin denied the existence of universals in an attempt to solve the problem of fictionalism. For Roscelin the universal (abstract term) was reduced to an emission of sound ('flatus vocis'), in conformity with Anicius Manlius Severinus Boethius' (ca. 480-524 or 525 CE) definition: 'Nihil enim aliud est prolatio (vocis) quam aeris plectro linguae percussio', meaning words do not mean more than the sound they make. Roscelin's universal corresponds to what is now called the "universale in voce" in opposition to "universale in re" and "universale in intellectu". Opposing both the extreme nominalism of Roscelin (ca. 1050-1125 CE) and the realism of William of Champeaux (ca. 1070-1122 CE), Peter Abelard (1079-1142 CE) taught a moderate doctrine; he recognized the universal as a symbol to which human beings have attached a commonly agreed significance, based on the similarity they perceive in different objects. With his theory of conceptualism, Peter Abelard attempted to synthesize nominalism and realism. Abelard's emphasis on the powers of reason, which he emphasized in his early years, led to his condemnation by Bernard of Clairvaux (1090-1153 CE). Peter Abelard believed that the truth of faith and reason must still agree, as did all his teachers, but reason has precedence. It is faith that has to adapt, i.e. the church must re-evaluate the meaning of its teachings when they fail to measure up to reason. Peter Abelard in his work Sic et Non (1122 CE) put forward: "dubitando enim ad inquisitionem venimus; inquirendo veritatem percipimus" (E: through doubting we come to questioning and through questions we perceive the truth) as a dialectical method of intellectual reflection or Socratic method that lays the arguments of two opposing points of view side by side for comparison. He challenged his readers to reconcile the authorities through dialectical reasoning. Abelard established rules for harmonizing conflicts and he emphasized the close examination of the meanings of words ("proprietas terminorum"). Abelard in his work did not answer the questions but only developed the method of arriving at an answer
(see also The Scholastic Culture of the Middle Ages, 1000-1300, John W. Baldwin, Heath and Co., 1971, p. 83). This would become the basis for the Scholastic disputatio. This early form of Abelard's Sic et Non method relies on the "empiricist axiom" (Aristotelian) that knowledge has its origin in sensory experience.

John of Salisbury (ca. 1115-1176 CE), an English scholar noted for his humanistic studies, was representative of the important work done at the noted School at Chartres. Hugh of Saint Victor (ca. 1096-1141 CE), a German scholar and mystic, urged the study of every branch of learning. His treatise On Sacraments was the first summa, an important medieval literary genre. The summae were comprehensive, intricately arranged works on theology and philosophy; they were characterized by their wide scope and vast learning. In his Didascalicon, Hugh of Saint Victor defines philosophy as a thorough investigation into the nature of all things, both human and divine: "Philosophia est disciplina omnium rerum humanarum atque divinarum rationes plene investigans". The Didascalicon selects and defines all of the important areas of knowledge, demonstrating that not only are these areas essentially integrated, but that in their integrity they are necessary for the attainment of human perfection and divine destiny. For Hugh of Saint Victor philosophy includes the sciences that consider the essences of things, sciences that consider mores, and sciences that present reasons for all human acts and desires. For him there are four major sciences (theoretical, practical, mechanical, and logical) from which all the other sciences are derived. For Hugh of Saint Victor logic, since the Greek term "λογος" in Latin meand both "ratio" and "sermo", includes logica rationalis (skill in thinking: dialectics, rhetoric), and logica sermonalis (the science of speech: grammar, dialectic, rhetoric). In the Didascalicon Hugh of Saint Victor also rejects nominalism in theology as this causes problems with regard to the status of the soul and the effect of the sacrifice of Jesus of Nazareth (7/2 BCE-30/36 CE) on humanity, when humanity is nothing more than a word in the nominalistic sense as opposed to realism. The Libri Quattuor Sententiarum (ca. 1150 CE), however, assembled by Peter Lombard (1095-1160 CE), was to become the classical source book for medieval theologians. It was a compilation of sources from the church fathers, especially Aurelius Augustinus (354-430 CE), and in subsequent years virtually every great medieval thinker wrote a commentary on the Sentences.

The areas of southern Europe which were conquered on the Muslims in the late 11^th century, particularly in central Spain (Reconquista) and Sicily, brought Western scholars into contact with lost texts of Greek philosophers. The Fourth Crusade (1202-1204 CE) ended in April 1204 CE, when the Crusaders of Western Europe invaded and sacked the Christian (Eastern Orthodox) city of Constantinople, capital of the Eastern Roman Empire (Byzantine Empire). On that occasion they also damaged the Imperial Library of Constantinople. The Reconquista (718 to 1492 CE) and the Fall of Constantinople (1453 CE) caused an influx of Greek philosophical works in Western (Latin) Europe, such as works of Plato and Aristotle which had previously been lost for Western scholars. The Muslims brought Aristotle to the West in the 12^th century, and Gerard of Cremona (ca. 1114-1187 CE) translated many Arabic texts into Latin. Willem van Moerbeke (1215-1286 CE) undertook a complete translation of the works of Aristotle from Greek into Latin or, for some portions, a revision of existing translations. The arrival of the Aristotelian corpus in Latin translation reopened the question of the relation between faith and reason, calling into question the modus vivendi that had existed for centuries. The already known philosophy and mainly the Aristotelian logic (Categories, De Interpretatione, Isagoge, Liber sex principiorum, De topicis differentiis, De divisione, De syllogismis categoricis and De syllogismis hypotheticis) was called the "logica vetus" ("l'arte vecchia", or "the old art") and the newly discovered works (Prior Analytics, Posterior Analytics, Topics, and Sophismata) would become known as the "logica nova" ("l'arte nova", or "the new art"). The full Organon of Aristotle now became available in Latin translation for the first time. Scholastics would make a distinction between the "Ars Definiendi" or "Disciplina Definiendi" (science of definitions) and "Ars Disputationum" or "Disciplina Disputandi" (art of debates) as parts of their method to arrive at truth through logical reasoning. In De Dialectica Augustinus of Hippo (354-430 CE), when educating his son, would lay the basis for this method of philosophy. The medieval philosophy would also define "Auctoritas aprobata" or authorities which were believed whose knowledge could be accepted without doubt as being true. This would in the end undermine the progression and viability of scholastic philosophy and its related theology.

The 13^th century is generally regarded as the golden age of medieval philosophy in Western Europe. It was marked by two important developments: the growth of universities, especially at Paris and Oxford, and the introduction of Aristotle into the West. Until then, only the early works of Aristotle had been known to Western scholars, and those in poor translations; between 1120 and 1220 CE virtually the whole body of Aristotle's work was rendered into Latin, mainly from Arabic translations. The impact on Western thinkers of this vast body of systematic thought and organized research and analysis was enormous. Western philosophy had lacked a consistent system to analyze the relation of thought (Trivium) to reality (Quadrivium). Only part of the logic of Aristotle had been available. The sciences of the Trivium (logic, grammar and rhetoric) reached their limits as they lacked the sciences of the Quadrivium (arithmetic, geometry, music, and astronomy) to connect to the real world. At the Cathedral School of Chartres, Neoplatonist philosophers like Bernard of Chartres (died after 1124 CE), Thierry of Chartres (died before 1155 CE), and William of Conches (ca. 1090-after 1154 CE) were part of the twelfth-century renaissance, pioneering the Scholastic philosophy. The Timaeus of Plato provided them with the basis for the much needed cosmology. Later however the Physics (350 BCE) of Aristotle would provide the required cosmology for the developing Neo-Aristotelian philosophy and theology. Also important was the influence of Avicenna (ca. 980-1037 CE) and Averroës or Ibn Rushd (1126-1198 CE), the two Arabic commentators whose interpretations of Aristotle were translated as well.

As a result of the discovery of new elements of Aristotelian logic, the so-called "Logica Nova", medieval philosophers developed a new Nominal and Terminist Logic (Logica Modernorum). Terminist logic has its focus on terms as the basic unit of logical analysis, and so it includes both supposition theory, together with its ramifications, and the treatment of syncategorematic terms in addition of categorematic terms (from κατηγόρημα or predicate). The development of nominalism would lead to the separation of the realist "old way" (via antiqua) and the nominalist "modern way" (via moderna).
(see also The Cambridge History of Medieval Philosophy Volume 1, Part II - Logic and language, Robert Pasnau (Ed.), Cambridge University Press, 2009). The medieval philosophers in their Terminist Logic developed the theory of the "proprietas terminorum" or the propertry of terminology as an addition to the rediscovery of the "Logica Nova" of Aristotelian logic. They distinguished between the "suppositio" and the "simplificatio". The "suppositio" signifies the inherent or essential meaning of something, while the "simplificatio" signifies the contextual meaning (suppositionum varietas). This was for instance used in the discussion about the intricacies of the divine Trinity: God is the "suppositio", while the Father, Son and Holy Spirit are the "simplificatio". Within the "suppositio" the medieval philosophers distinguished between the "suppositio simplex", "personalis" and "materialis"
(see also Reference and Anaphoric Relations, H.K. von Heusinger (Editor) and U. Egli (Editor), Studies in linguistics and philosophy, Volume 72, Springer, 1999, p. 34). The early authors which developed the theory of the "proprietas terminorum" were Peter Abelard (1079-1142 CE), Petrus Helias (ca. 1100-after 1166 CE) and Petrus Hispanus (13^th century). Later on the "Logica Modernorum" would be developed by philosophers such as the English philosophers Walter Burley (ca. 1275-1344 CE), William of Ockham (ca. 1288-1348 CE), Thomas Bradwardine (ca. 1290-1349 CE) and William of Heytesbury (ca. 1313-ca. 1372). In Paris Jean Buridan (ca. 1300-ca. 1358) would also contribute to the development of the logica moderna. Paulus Venetus (1368-1428 CE) in his Logica magna would provide a overview of the achievementss of the medieval logica moderna.
(see also Logic - The Medieval Latin West, 1200-1500 and Contributions to coparative mythology, Selected Writings VII, Roman Jakobson, Mouton, 1985, p. 195). Several authors would write so-called Parva Logicalia on branches of non-Aristotelian logic, which were treated in the various supplements added from time to time to the Summulae logicales (tract VII) of Petrus Hispanus. The treatises incude works on supposition (suppositio), relative terms (simplificatio), ampliation, appellation, restriction and distribution. Peter Abelard's theory of universals would predate the development of Terminist Logic (Renaissance and Renewal in the Twelfth Century, Charles Homer Haskins, Medieval Academy of America, 1991, p.492). Petrus Hispanus wrote a textbook on logic, the Tractatus or Summulae logicales magistri Petri Hispani consisting of two main parts. One part deals with doctrines found in the Logica Vetus (old logic) and Logica Nova (new logic) of Aristotle, while the scond part contains doctrines covered by the logica modernorum or the proprietates terminorum (properties of terms)
(see also Logica modernorum:a contribution to the history of early terminist logic, Volume 6, Lambertus Marie de Rijk, Van Gorcum, 1962). Petrus Hispanus defined the "significatio" as the representation of a thing by means of a word in accordance with convention. The "suppositio" refers to a term as actually used in some context is dependent on significatio and can only occur via a term that already has some significatio. He also divides the "suppositio" into several categories, such as into "suppositio communis" (common supposition) and "suppositio discreta" (discrete supposition), etc. . Thomas Maulvelt with his Questiones Libri Porphirii and Marsilius of Inghen (1340-1396 CE) would make important contributions to the Parva Logicalia
(see also Renaissance philosophy, C. B. Schmitt, Cambridge University Press, 1988, p.147).

Prior to 1050 CE, schools were in monasteries and cathedrals. The monastery schools were predominate initially; they were founded beginning with the Carolingian Renaissance of the Carolingian Dynasty, but it was the cathedral schools that grew into universities in the High Middle Ages. The oldest four universities are the University of Salerno (9^th century CE), the University of Bologna (1088 CE), the University of Paris (1160 CE), and the University of Oxford (1167 CE). The University of Paris became a leading center for the study of Aristotle and attracted scholars from all over Europe; the Dominicans (Order of Preachers) and Franciscans (Friars Minor), popular new religious orders, played a leading role in the expansion of the universities and the development of scholasticism. These mendicant orders, or begging orders, were a response to the growing medieval cities and their tendency to independence and alleged heresies. These orders were part of the reforming movement within the church. The medieval University of Paris grew out of the cathedral schools of Notre-Dame and, like most other medieval universities, was a kind of corporate company that included both professors and students. The papal bull Parens scientiarum (E: The Mother of Sciences) was issued by Pope Gregory IX (ca. 1145-70-1241 CE) on 13 April 1231 as a response to the University of Paris strike of 1229. The bull assured the independence and self-governance of the University of Paris from local authorities, and placed it directly under papal patronage. With papal support, Paris soon became the great transalpine centre of Christian orthodox theological teaching as a response to deviant philosophical and theological developments. The systematization of the scholastic studies consisted of the following elements: lectio, quaestio and disputatio. It was in the universities that the two traditional forms of scholastic literature were developed: the question (the 'quaestio assignata' is a thesis that is posed and defended against objections) and the commentary. Scholasticism paid utmost respect to authority. All the subject matter taught at the university used an authority as a launching pad for investigations. For instance, the study of Theology was based on the authority of the Scriptures and the Early Church Fathers. On the other hand, Roman Law was based on the body of work of the Emperor Justinian I (ca. 482-565 CE), while Logic was Aristotelian. Although Aristotle's work was of central significance in the development of scholasticism, it did not make its way without difficulties. In 1210 and 1215 CE papal authority prohibited the teaching of some of Aristotle's works at the University of Paris, although by 1240 the ban was no longer enforced. The University of Padua (1222 CE) would become an important center for the study of Averroism and Alexandrism. On 18 January 1277, Pope John XXI would request an examination of rumors of heresy at the University of Paris. On 7 March 1277, the Bishop of Paris, Étienne Tempier (died 1279 CE), prohibited the teaching of 219 philosophical and theological Aristotelian and Averroist theses, such as concerning the unity of intellect, causal necessity, and the eternity of the world. The condemnations against Aristotelianism in Paris involved Giles of Rome (ca. 1243-1316 CE), Siger of Brabant (ca. 1240-1280 CE), Boethius of Dacia (fl. 13th century CE), the arts faculty, and certain doctrines of Thomas Aquinas (1225-1274 CE). His decree however was actively opposed and eventually overturned in 1325 CE. Philosophers would continue to get to the wrong conclusions with regard to matters which were important for (Roman Catholic) faith, but this could be handled with by the development of more and better dogma's and the Index Librorum Prohibitorum.

The systematization of the scholastic studies consisted of the following elements: lectio, quaestio and disputatio. Teaching was bases on reading (legere) of texts of "Auctoritas aprobata" and quotations. From 1215 on at the University of Paris, there existed two ways of reading (lectio): "cursorie" and "ordinarie". The basic texts to read were the Libri Quattuor Sententiarum of Petrus Lombardus (1095-1160 CE) for theology; the works of Aristotle for philosophy; and Avicenna's (ca. 980-1037 CE) Canon of Medicine (1025 CE), in the Galenic tradition, for medicine. While the "lectio" was meant for the receptive or listening student, the "quaestio" was meant to make the student doubt and think (Socrates' aporia). Anicius Manlius Severinus Boethius (ca. 480-524 or 525 CE) had defined the "quaestio" as a "propositio dubitabilis", raised as a two part question (utrum... an). Peter Abelard (1079-1142 CE) in his work Sic et Non (1122 CE) put forward: "dubitando enim ad inquisitionem venimus; inquirendo veritatem percipimus". The two parts of the "propositio dubitabilis" together created a dichotomic contradiction and the discussion was along the lines of the dialectical "pro" and "contra". The Medieval "quaestio" grew out of problems which arose out of a lectio with conflicts between the position of "authorities", mainly in their "dubia" at the end of a "lectio". Gradually the "quaestio" became independent from the "lectio" and developed into the disputatio. The two types of disputations were the "quaestio disputata" (disputed questions), which was a disputed question, and the "quaestio de quodlibet" or "disputationes quodlibetales", which was publicly disputed by magisters, whereas the disputed questions or 'quaestio assignata' were mainly meant for students. The Scholastic system of education of the Middle Ages, was also based on these "disputationes" (E: disputations), which offered a formalized method of debate. The disputations only allowed for those topics which were considered "dubitabile", for instance problems with regard to certain "Auctoritas aprobata" which were allowed to be doubted or reqired investigation. The empirical material for the debates were Scripture, dogmata and the "Auctoritas aprobata" for theological debates and first principles and "Auctoritas aprobata" for scientific debates (as long as they did not contradict Scripture and dogmata). The "disputatio" was started by the Magister with a "quaestio" or "propositio dubitabilis" which started with "utrum..., an...?" (whether) for a thesis which was to be investigated. The two parts of the question also formed a dichotomic contradiction. The discussion within the frame of the "quaestio" was regulated by the dialaectics of "pro" and "contra". The magistri, baccalaurei and students participated in the debate. The proponens gave the arguments "quod sic" and the opponens gave the arguments "quod non". Finally the Magister (Professor) draws the "determinatio magistralis" (final conclusion), which was written down in a "quaestio disputata". Thomas Aquinas (1225-1274 CE) would use the structure of the disputation in his "summa", which started with a "quaestio", then proceeded with the "objectiones" which the author replies to with a "Sed contra...". In the "corpus" the Magister replies with a "Responsio" or "Respondeo dicendum". Finally with the "Ad primum (secundum, etc.) dicendum quod...", the necessary "responsiones ad objecta" the Magister refutes the objections or the antagonism disappears by making it part of a larger "truth". The Magister makes an effort to embody the truth that the opposing position contains, within a wider framework which, far from casting it aside, underwrites its truthfulness
(see also Saint Thomas Aquinas: the person and his work, Volume 1, Jean-Pierre Torrell, Robert Royal, CUA Press, 2005, p. 60 and Contemporary Philosophical Discourse in Lithuania, Jurate Baranova, CRVP, 2005, p. 23).

The first Western Aristotelian was Albertus Magnus (1193/1206-1280 CE), who was an important student of the natural sciences as well. But the leading figure in the movement to "Christianize Aristotle" was Thomas Aquinas (1225-1274 CE), the Doctor Angelicus, a Dominican and one of the greatest intellectual figures of the Middle Ages. Thomas Aquinas would create the synthesis of Western Christian doctrine and the newly re-discovered philosophy of Aristotle. The result of his work was a new modus vivendi between faith and philosophy which survived until the rise of the new Copernican astronomy and Newtonian physics. Thomism would become the dominant Roman Catholic philosophy. He produced a vast body of philosophical work, which was remarkably precise, detailed, and organized. Denying any basic conflict between faith and reason, Aquinas sought to demonstrate that reason could lead man to many of the great spiritual truths and could help him to understand those truths that he accepted on faith. Aquinas refused to believe that nature abounds in unnecessary things. This doctrine of efficient causation, which became the cornerstone of Aquinas's philosophical system, known as Thomism, gave the supernatural supremacy over the natural, but by implication the natural and supernatural worlds were separate if not independent. He combated secular interpretations of Aristotle, especially "Latin Averroism", the doctrines of Siger of Brabant (ca. 1240-1280 CE) and Boetius of Dacia (13^th century CE). The basic tenet of Latin Averroism was the assertion that reason and philosophy are superior to faith and knowledge founded on faith. Aquinas attacked the doctrine of monopsychism and panpsychism (as opposed to emergentism) in his work De unitate intellectus contra Averroistas. In particular, Aquinas attacked the Averroist teaching that denied the immortality of the individual soul. Aquinas himself was vigorously opposed by the Franciscans, led by Bonaventure of Bagnoregio (ca. 1217-1274 CE). Bonaventure, rooted in an older theological tradition, feared the excesses of reason in its contact with faith and almost succeeded in having Aquinas' teachings condemned at Paris. Bonaventure revisited Augustinian method appealing to illumination and mysticism over the Aristotelian inquiry which was a Thomistic tool.

Another Franciscan opponent of Thomas Aquinas was John Duns Scotus (1265/1266-1308 CE), the Doctor Subtilis, who developed a new scholastic synthesis. He argued that natural reason is limited in its ability to penetrate matters of faith, thus separating philosophy and theology. John Duns Scotus worked on natural theology, metaphysics, the theory of knowledge, and ethics and moral psychology. The doctrines for which he is best known are the "univocity of being", that existence is the most abstract concept we have, applicable to everything that exists; the "formal distinction", a way of distinguishing between different aspects of the same thing; and the idea of "haecceity", the property supposed to be in each individual thing that makes it an individual (individuation of universals in particulars). Scotus agreed with Thomas Aquinas that all our knowledge of the divine starts from creatures, and that as a result we can only prove the existence and nature of the divine by what is an argument 'quia' (reasoning from effect to cause, induction), not by an argument 'propter quid' (reasoning from essence to characteristic, deduction). In his Ordinatio Scotus however puts forward a number of arguments for univocal predication with regard to divinity and against the Thomistic doctrine of analogy. His early works (parva logicalia) are commentaries on Aristotle, but his most important work are his commentaries, Ordinatio or Opus Oxoniense, on the Libri Quattuor Sententiarum of Peter Lombard (1095-1160 CE). Accepting universals as an extra-mental reality common to particulars (realism), Scotus had to solve the problem of distinct exemplifications of that extra-mental reality or its individuation. With regard to universals (natura communis) John Duns Scotus postulated that they exist as such and within particulars by means of individuation ("thisness" or haecceitas). For example the common nature 'humanity' exists in both Socrates and Plato (synchronicity), although in Socrates it is made individual by Socrates's haecceitas and in Plato by Plato's haecceitas. The presence of actual essence (formalia) completely within particulars and not only potential essence for Scotus, poses problems with regard to its relation to diachronicity or change in time, as opposed to the other position of essence being only present in its potentiality. In his concept of formal distinction Scotus made a distinction between distinction 'in re' (which differentiates separate essences) and the distinction 'in mente' (grammatical distinctions and logical distinction between equivalent concepts). In addition he postulated the 'distinctio formalis ex parte rei' (real attributive but not essential differences, eg. whiteness and sphericity of a ball) and the 'disctinctio formalis modalis' (distinction between a form and its intrinsic modality or variability in particulars, e.g. degrees of whiteness). By making these distinctions, Scotus allows for real diversity in particulars without proliferating entities or dividing essence itself. When moving from universal to particular instantiation, the formal distinction approach of Scotus is a way to solve the problem of individuation and of preserving ontological unity within a realist approach to universals.

Ramon Llull (ca. 1232-ca. 1315 CE), the "Doctor Illuminatus", was a Majorcan writer and philosopher, logician and a Franciscan tertiary. He wrote the first major work of Catalan literature. His Ars generalis ultima or the Ars Magna (1305 CE) was meant as a debating tool for winning Muslims to the Christian faith through logic and reason. The principles of the Ars generalis ultima were developed further by Giordano Bruno (1548-1600 CE) in the 16^th century, and by Gottfried Wilhelm Leibniz (1646-1716 CE) in the 17^th century for investigations into the philosophy of science. Leibniz gave Llull's idea the name "ars combinatoria" in his Dissertatio de arte combinatoria (1666). Ramon Llull held that a man, in order to find out the truth about God, must bring reason to the task as well as faith, thereby breaking down the distinction between natural and supernatural truth.

William of Ockham (ca. 1287-1347 CE), another Franciscan, is generally regarded as the last of the great medieval philosophers. By firmly separating philosophy and theology and insisting that there is no rational ground for faith, he brought an end to that synthesis of faith and reason that characterized the greatest scholastic thought
(see also William of Ockham: The metamorphosis of scholastic discourse, Gordon Leff, Rowman and Littlefield, 1975). Thomas Aquinas had perfected the great "medieval synthesis" of faith and reason and this viewpoint was canonized by the Roman Catholic Church. Ockham on the contrary embraced fideism, the view that belief in God is a matter of faith alone. He believed that human reason can prove neither the immortality of the soul nor the existence of God (nor his unity and infinity), and that these truths are known to man by Revelation alone. Ockham taught that universal terms are merely names which are attached to particular things, and that universal terms are merely linguistic devices which we use to try to understand reality (flatus vocis). Singular things, and not universals, are the original objects of cognition. Singularities precede universalisation (concepts) and not the other way around, where universals are independent entities which precede particulars. The essence is in the particular and not in the universal. In his approach to metaphysics and epistemology, Ockham used a method of logical empiricism, asserting that intuitive knowledge is prior to abstractive knowledge, and that abstractive knowledge must be based on intuitive knowledge. He had an important influence on modern empiricist philosophy. His philosophical writings included the Summa Logicae (Summa of Logic, ca. 1328 CE), the Expositio in libros Physicorum Aristotelis (Exposition of the Books of Physics of Aristotle (1322-1324 CE), and the Tractatus de praedestinatione et de praescientia Dei et de futuris contingentibus (Treatise on Predestination and on God's Foreknowledge of Future Contingents (1321-1324 CE). His theological works included the in those day traditional In Libros Sententiarum (Commentary on the Sentences of Peter Lombard (1317-18 CE), and the Quodlibeta Septem (Seven Quodlibets, 1322-1325 CE). His political writings included the Dialogus Inter Magistrum et Discipulum de potestate Papae et Imperatoris (Dialogue between Master and Disciples on the Power of Emperors and Popes, 1334-1347 CE), and his Octo quaestiones de potestate papae (Eight Questions on the Power of the Pope, 1340-1344 CE).

In his work Summa Totius Logicae (E: Sum of Logic) on logic Ockham puts forward his nominalist or conceptualist view on universals. Ockham rejects the view of John Duns Scotus (1265/1266-1308 CE) that universals have a formal existence outside the mind, and that universals correspond to real things in the empirical world. Ockham argues that, according to this view, singulars and universals are formally distinct, but not really distinct. Ockham contends that individual difference cannot be the same as common nature, and that singulars and universals are really distinct and different things. For Ockham the universal (first and second 'intention') is a signifying 'act of the understanding' and has no real existence (nominalism or conceptualism). There can be no extramental existent universals. Everything general in the created world exists only in the intellect and only particulars ahve real existence. This constitutes a separate order of being for universals from real things in the world. He also adopted the distinction between 'first intention' and 'second intention'
(see also Quodlibeta Septem IV, 19) with regard to universals. Terms of first intention refer to things which are not signs of a language, but things for themselves. Terms of second intention refer to signs of other signs in the language or to natural signs (concepts). In other words, terms of second intention stand for terms of first intention
(see also The Cambridge History of Later Medieval Philosophy: From the Rediscovery of Aristotle to the Disintegration of Scholasticism, 1100-1600, Norman Kretzmann (Editor), Anthony Kenny (Editor), Jan Pinborg (Editor), Eleonore Stump (Editor), Cambridge University Press, 1982, p. 492 and The Terms "Prima Intentio" and "Secunda Intentio" in Arabic Logic, Kwame Gyekye, Speculum Vol. 46, No. 1 (Jan., 1971), pp. 32-38).

Ockham regards logic as a 'scientia sermocinalis', that is, as an organized body of knowledge concerned with meaningful language (Central Works of Philosophy (Vol. 1), Peter King, Acumen 2005: 243-XXX). Part I of the Summa Totius Logicae is devoted to terms and is concerned with semantics; Part II is devoted to sentences, which are made up out of terms, and is concerned with truth; Part III is devoted to arguments, which are made up out of sentences, and is concerned with inference. In the fist part of the Summa Totius Logicae he writes about the Praedicamenta (E: Categories) of Aristotle. As Ockham denies that universals exist independently in reality as such, he regards them to be merely names or 'nomina' ('post res'). William of Ockham, like Aristotle (384-322 BCE) and Anicius Manlius Severinus Boethius (ca. 480-524 or 525 CE), holds that there are three distinct levels of language: Written, Spoken, and Mental Language, associated respectively with the activities of writing, speaking, and thinking (trias grammaticus). Concepts in Mental Language, for William of Ockham, are by definition related to the things of which they are the concepts. These concepts are by definition related to the things of which they are the concepts (signification). The 'grammar' of Mental Language is its semantics and it acts by means of the images it brings forward in the mind. Mental Language contains primitive (corpuscular) elements and complex expressions formed out of them by logical operations or syllogisms. William of Ockham distinguishes between absolute elements ('substantia') and qualitatieve terms (predicates). In addition he deals with connotative terms which connect 'substantia' and as such are not absolute in themselves. By developing a theory of supposition William of Ockham bridges the gap between signification and truth and from which he develops a reductive ontology (Occam's razor). Part II of the Summa Totius Logicae is devoted to sentences and their truth conditions. In Part II he deals with modality involving reference to simultaneous alternatives. Sentences are divided into simple and compound (hypothetica) sentences. Simple sentences are are Aristotelian assertoric categorical sentences, consisting in a subject-term (substantia), a copula ('is' or 'has'), and a predicate-term (attribute, Aristotelian category). Sentences with respect to mode may be assertoric (certain, true) or modal, that is, they may explicitly involve possibility or necessity. With respect to tense, William of Ockham recognizes past, present, and future tenses as irreducibly different. Both modal and tensed sentences may involve "ampliation" or widening of their meaning beyond certainty and into probability (e.g. composite modal sentences). Part III of the Summa Totius Logicae is devoted to inference (syllogisms) in general. Inferences are sequences of sentences that have or lack certain properties. He disscusses the traditional assertoric syllogism and develops the modal syllogism based upon composite modal sentences (which can be reduced to multiple ordinary modal sentences) and ordinary modal sentences. William of Ockham clarifies if syllogisms hold, depending on whether a a modal sentence is read as affecting the supposition of the subject-term or not. This is done by reducing syllogisms with modal sentences (modal inference) into assertoric syllogisms. Ockham develops a general theory of inference, which is found in his treatment of consequences.

In his Quodlibeta Septem (1487) and Summa Totius Logicae (1488) Ockham made some contributions to the development of the theory of the "proprietas terminorum" or proper use of terms in Aristotelian logic. A suppositio or term can be said to be 'material' (suppositio materialis), it can signify a particular individual (suppositio personalis) or a term can be the actual concept in the mind (suppositio simplex).

For William of Ockham universals do not exist as extramental entities themselves, but are merely words, as opposed to realism. This solves the problem of individuation which exists in realism with regard to relation of universals to particulars, but causes problems for the concept of identity which is reduced to similarity as in nominalism no universal (natura communis) exists independently to explain identity. With regard to quantity as a connotative attribute which links the essence of a substance to the other attributes (categories), William of Ockham discusses the problem of rarefactio (expansion of an essence with keeping its identity) and condensatio (shrinking of an essence with keeping its identity) with regard to quantity as an attribute of essence. Quantity can be either added or continuously destroyed and created, but the second option is rejected by Ockham, because it creates problems with regard to the relation of the essence and attributes through the cycles of destruction and creation.

In his Quodlibeta Septem (1322-1325 CE) Ockham would also deal with aspects of essence and his view on universals, such as the status of quantity as a special connotative quality connecting the essence and its attributes (qualities), both close to the essence and relating the essence to its spatial extendedness and its qualities in the world. In his nominalist view quantity was not required as the quality providing individuation to universals as in a realist concept of universals. For Ockham transubstantiaton was also possible when adhering to a nominalist viewpoint.

The Augustinian nominalist Gregory of Rimini (ca. 1300-1358 CE) united the Oxonian (Oxford) and Parisian (Petrus Aureolus) traditions in 14^th Century philosophy and founded the via Gregorii school of thought, which would also influence Martin Luther (1483-1546 CE) and Jean Calvin (1509-1564 CE). After the 15^th century the reputation of medieval philosophy declined. But the break between medieval philosophy and Renaissance thought was mainly in the area of metaphysics; scholastic tradition and methods continued to be followed in politics and law, in canon law, civil law, and common law and, later, in the development of international law. In the late 15^th century the Dominicans began a Thomistic revival; its brilliant leader was the reformer Tommaso de Vio Gaetani Cajetan (1469-1534 CE).

- Figura paradigmatica, De Coniecturis, Nicolaus Cusanus -

In the late Middle Ages philosophers such as Nicolaus Cusanus (1401-1464 CE) would start to move awy from the Scholastic way of thinking. Cusanus accompanied Basilios Bessarion (1403-1472 CE) on his way from Byzantium to the Council of Florence, which was an attempt to end the East-West Schism of 15 July 1054 CE. This journey brought Cusanus into contact with Byzantine theology, the 'Via Negativa' and Neoplatonism
(see also Tracing Nicholas of Cusa's early development. The relationship between De concordantia catholica and De docta ignorantia, Jovino de Guzman Miroy, The Journal of Ecclesiastical History, Vol. 61, Issue 03, July 2010, pp 624-625). The inspiration for De Docta Ignorantia came on the boattrip from Byzantium to Italy with the Byzantine delegation. Nicolaus Cusanus in De Docta Ignorantia (1440, On learned ignorance/on scientific ignorance) described the learned man as one who is aware of his own ignorance. For Cusanus both reason (ratio) and a supra-rational understanding (intellectus) were needed to understand God and to find the way back from plurality to unity. Cusanus relates the coincidence of opposites, absolute/contracted and enfolding/unfolding to relate God and creation. Dilaectic reasoning brings man from reality rowards God, however the exactness of truth cannot be attained. This resembles the Neoplatonic idea that the Good pervades everything and can be found in reality from which man can ascend towards the Good.
(see also Neoplatonism & Christian Thought, Volume 2, Dominic J. O'Meara, State University of New York Press, 1982, p.154). This leads to the 'coincidentia oppositorum' (coincidence of opposites) or revelation of the oneness of things previously believed to be different. In De coniecturis (On Conjectures) Cusanus makes explicit the limits of human knowing. In De coniecturis Cusanus puts forward: "Conceive of a pyramid-of-light as progressing into darkness and of a pyramid-of-darkness as progressing into light; and reduce to [that] figurative conception everything that can be investigated, so that by guidance from what is perceptible you can turn your surmise toward hidden [truths]. And in order that you may be aided by means of an example, consider the universe as reduced to the diagram here below. Notice that God, who is Oneness, is as the base-of-light; but the base-of-darkness is as nothing. Every creature, we surmise, lies between God and nothing" (see On Surmises (De Coniecturis), translated by Jasper Hopkins, p182 and The Contradiction Between Form and Function in Architecture, John Shannon Hendrix, Routledge, 2013).

The University of Paris, like many universities, remained a spokesman for Roman Catholic orthodoxy, and its educational program, which was founded on scholastic dialectics, became rigidly fixed. As a result, the university made little contribution to the humanistic studies of the Renaissance, and the university subsequently declined under the impact of the Protestant Reformation and the ensuing Counter-Reformation. The Philipp University of Marburg, Europe's first Protestant university, was founded in the city of Marburg in 1527.

The metaphysical and theological crisis within late mediaeval Christianity resulted in the nominalist revolution. Prior to nominalism, Christianity was defined by scholastic philosophy, which posited the real existence of universals: reality was ultimately not composed of particulars but of universal categories of divine reason. The experience of the world as universal categories became articulated in syllogistic logic that, according to mediaeval belief, corresponded to divine reason. Man was believed to be created by God as a rational animal (animal rationabile) in the image of God (Imago Dei) and guided by a natural goal and divinely revealed supernatural one. Contrary to the scholastics, the nominalists believed reality was composed not of universal categories but of particulars. The universal is reduced to an emission of sound (flatus vocis). Language did not point to universal categories but was merely signs useful for human understanding; creation was particular and therefore not teleological; and God could not be understood by human reason but only through Biblical revelation or mystical experience
(see also Bible, Romans 11:33 - "o altitudo divitiarum sapientiae et scientiae Dei quam inconprehensibilia sunt iudicia eius et investigabiles viae eius"). Nominalism challenged and eventually destroyed the great synthesis that started with the Church Fathers that combined the reason of Greek philosophy with the Christian revelation. This new vision of God that arose in the fourteenth century emphasized divine power and its unpredictability rather than divine love and predictable reason, a change that reflected the historical realities of the time with the Western Schism (1378-1417 CE), the Hundred Years War (1337-1453 CE), and the Black Death (1346-1353 CE). With its success, nominalism eventually paved the path for 'modernity'. Because it provided a new conception of God, man, and nature, nominalism was revolutionary. While it was able to undermine scholasticism, nominalism was ultimately incapable of providing a broadly acceptable alternative to the comprehensive world view it had destroyed. The failed attempts to find such an acceptable world view has characterized Western history since the fourteenth century: humanism, the Reformation, and modernity itself. Attempts to create a new synthesis were made by Francesco Petrarca (1304-1374 CE) and Renaissance humanism, Martin Luther (1483-1546 CE) and the Protestant Reformation, and early modernity with the dualism of René Descartes (1596-1650 CE) and the materialism of Thomas Hobbes (1588-1679 CE). Isaac Newton (1642-1727 CE) with the publication of his Philosophiæ Naturalis Principia Mathematica in 1687, and "Newtonianism" would provide a new synthesis between God, man, and nature out of which modern Western culture would emerge
(see also The Theological Origins of Modernity, Michael Allen Gillespie, Chicago: University of Chicago Press, 2009 and Mediaeval and Renaissance Logic, Dov M. Gabbay, John Woods, Elsevier, 2008, p. 389 and How Greek Philosophy Corrupted the Christian Concept of God, Richard R. Hopkins, Cedar Fort, 2009, p. 393 and Luther as Nominalist: A Study of the Logical Methods Used in Martin Luther's Disputations in the Light of Their Medieval Background, Graham White, Luther-Agricola-Society, 1994 and The depravity of wisdom: the Protestant Reformation and the disengagement of knowledge from virtue in modern philosophy, Mark A. Painter, Ashgate, 1999 and Sir Isaac Newton's Mathematical Principles of Natural Philosophy and His System of the World: The system of the world, Sir Isaac Newton, University of California Press, 1962, p. 545).

The crisis of mediaeval Scholasticism is also reflected in the personal crisis of Thomas Aquinas (1225-1274 CE) at the end of his life, when he realized that "All that I have written seems like straw compared to what has now been revealed to me" after a mystical experience while saying mass on 6 December, 1273. In 1273 Thomas Aquinas suddenly gave up writing the Summa Theologiae and immersed himself in absolute silence. When asked by his secretary Reginaldo da Pipperno (ca. 1230-1290 CE) for the reason of his silence he gave the answer "Mihi videtur ut palea". He had realized that his attempt to found faith on a rational discourse, based on Aristotelian philosophy (via positiva) was futile. His crisis was based on realising that the (scholastic) way that was expected to give firm root into the divine reality revealing itself in the Holy Scripture is the way rather leading to the de-realized sphere of "hohlen Wortanalyse" (flatus vocis)
(see also Contemporary Philosophical Discourse in Lithuania, Jurate Baranova, CRVP, 2005, p. 22 and The Principle of Analogy in Protestant and Catholic Theology, Battista Mondin, Springer Science & Business Media, 2012, p. 100).

Resources for Medieval Studies
On-line Reference Book for Medieval Studies
Muslim Scientists and Scholars
Byzantium
Byzantine and Medieval Studies Sites

Abu Hamid al-Ghazali - (505-1111 CE)
Thabit Ibn Qurra - (836-901 CE)
Abu Bakr Muhammad Ibn Zakariya al-Razi - (865-925 CE)
Abu Bakr Muhammad Ibn Zakariya al-Razi - (865-925 CE)
Abu Al-Nasr Al-Farabi - Abu Nasr (c.870-950 CE)
Avicenna - Ibn Sina (980-1037 CE)
Averroes - Ibn Rushd (1126-1198 CE)
Solomon Ibn Gabirol - Avicebron (1021-1058 CE)
Ibn Khaldun - (1332-1395 CE)
Kitab al 'Ibar, The Muqaddimah - Ibn Khaldun

Michael Psellos - (1017-1078 CE)
Chronographia - Psellos
Anna Comnena - (1083-1135)
The Alexiad - Anna Comnena
Theodoros Metochites - (1270-1332 CE)
George Gemistos Plethon - (1355-1452 CE)
Georgios Kourtesios Scholarios - (ca. 1400-ca. 1473 CE)

Scholasticism - (1100-1500 CE)
Anselm of Canterbury - (1033-1109 CE)
Albertus Magnus or Albert the Great - (1193-1280 CE)
Thomas Aquinas - (1224-1274 CE)
John Duns Scotus - (1265/66-1308 CE)

Renaissance Philosophy

Georgius Gemistus or Plethon (ca. 1355-1452/1454 CE)
Painting by Benozzo Gozzoli Corteo dei Magi Palazzo Medici-Riccardi, Firenze, Italy.

Col viso ritornai per tutte quante
le sette spere, e vidi questo globo
tal, ch’io sorrisi del suo vil sembiante;
- Dante, Paradiso, Canto XXII, 133-135 -

The Renaissance was an historical age that followed the Middle Ages, preceded the Protestant Reformation and spanned roughly the 14^th to the 17^th century. Several events contributed to the transition of the medieval world view to the Renaissance. The mediaeval world-view would make way for a more individualistic view on human life, which changed the relation between, God, man and nature. The Black Death, when between 1346-1353 CE about one third to one half of Europe's population was destroyed, had a profound influence on the perceived relation between God and man and the perceived order in Nature and society. The mediaeval world was bereft of its intrinsic divine ordering and the will of God came to have an extrinsic relationship to the world, which was rendered passive, neutral and dead (read: mechanical) in itself. This meant that the perceived order was ultimately derived voluntaristically, rather than being inherent to creation by virtue of its original design. The metaphysical and theological crisis within late medieval Christianity manifested itself in the nominalist revolution. Nominalism became an alternative to medieval realism, which paved the way for modernity. Renaissance humanism and the Reformation, were the first attempts to answer the fundamental questions about God, man, and nature that arose out of the nominalist revolution as a result of the metaphysical and theological crisis within late medieval Christianity. The concept of the infinite universe would change the relation between the Universe and God. The removal of the earth from the centre of the Universe to a planet circling the Sun would have profound theological consequences. The ascent of mathematical physics, astronomy and the mechanistic world-view would challenge the concept of free will with determinism. It would take until the early modern era to rebuild a world-view which was capable to deal with the emerging uncertainty. However the mediaeval synthesis of science, philosophy and theology would suffer in the process
(see also The Black Death Transformed: Disease and Culture in Early Renaissance Europe, Samuel Kline Cohn, Bloomsbury Academic, 2003 and Late Medieval and Renaissance Philosophy, Frederick Copleston, A&C Black, 2003, p. 122 and The Scientific Renaissance 1450-1630, Marie Boas Hall, Courier Corporation, 2013 and Transcending Boundaries in Philosophy and Theology: Reason, Meaning and Experience, Kevin Vanhoozer, Martin Warner, Ashgate Publishing, Ltd., 2013, p. 98).

The Renaissance started in Florence (Italy) and spread to the rest of Europe. The Fall of Constantinople on 29 May 1453 CE, when the city was conquered by the Ottomans marked the end of the Middle Ages and the beginning of the Renaissance. Many Greek scholars fled to Italy (Florence) and with them brought Greek texts and knowledge to Western Europe. The rediscovery of old Latin texts, such as De rerum natura written by Titus Lucretius Carus (ca. 99-ca. 55 BCE) and other classical Latin manuscripts, mostly decaying and forgotten in German, Swiss, and French monastic libraries, lead to a revival of classical literature. Many of those manuscripts which had been copied during the Carolingian Renaissance and the 12^th century, only survived in monastic libraries. The debate between logicians and grammarians continued from the mediaeval tradition into the Renaissance. The logician pretends he has no need of grammar, whereas the grammarian does need logic. For logic enquires into the meaning, whereas grammar enquires into the utterance
(see also The Fall of Constantinople to the Ottomans: Context and Consequences, Michael Angold, Routledge, 11 jun. 2014, p. 104 and Carolingian Learning, Masters and Manuscripts, John J. Contreni, Ashgate Publishing Company, 1992 and Renaissance and Renewal in the Twelfth Century, Robert Louis Benson, Giles Constable, Carol Dana Lanham, Charles Homer Haskins University of Toronto Press, 1991 and De Rerum Natura: The Latin Text of Lucretius, William Ellery Leonard, Stanley Barney Smith, Univ of Wisconsin Press, 2008, p. 108 and Routledge History of World Philosophies, Volume 1, Seyyed Hossein Nasr, Taylor & Francis, 1996, p. 900 and Aristotelian Logic and the Arabic Language in Alfarabi, Shukri Abed, SUNY Press, 1991, p. xvi).

The Council of Florence or Council of Ferrara (1431-1441 CE) brought Western philosophers in contact with Byzantine and Platonic philosophy, which had largely been lost in Western Europe where only a remnant of Platonism had survived. The Renaissance brought a revival of Platonism, due to the influence of men from the Byzantine Empire like Cardinal Basilios Bessarion (1403-1472 CE) and Georgius Gemistus Plethon (ca. 1355-1452/1454 CE) and Italians like Marsilio Ficino (1433-1499), Giovanni Pico della Mirandola (1463-1494 CE) and his nephew Giovanni Francesco Pico della Mirandola (1470-1533). The philosopher Pietro Pomponazzi (1462-1525 CE) would play an important role in the renewal of the Aristotelian or Peripatetic tradition. The Italian Renaissance of the 15^th century represented a reconnection of the west with classical antiquity, the absorption of knowledge from Arabic Culture, (Byzantine) Platonism, Pythagorean numerology, Hermeticism and Christian Cabala.
(see also Neoplatonism of the Italian Renaissance, N. A. Robb, Octagon Books, 1935 and Ficino and Renaissance Neoplatonism, K. Eisenbichler, O. Z. Pugliese, Dovehouse Editions Canada, 1986).

Francesco Petrarca (1304-1374 CE) an Italian scholar and poet, and one of the earliest humanists is often called the "Father of Humanism ". Seeking a middle way between religious austerity and worldly excess, Petrarch offered the portrait of the virtuous, solitary individual who attained dignity through self-mastery. For Petrarch, the divine could be realized in the individual rather than the political or religious life. His letter The Ascent of Mount Ventoux To Dionisio da Borgo San Sepolcro, about his ascent of mount Ventoux on 26 april 1336, captured the spirit of the Renaissance. In the letter he quotes from the Confessiones (X:8) of Aurelius Augustinus (354-430 CE): "And men go about to wonder at the heights of the mountains, and the mighty waves of the sea, and the wide sweep of rivers, and the circuit of the ocean, and the revolution of the stars, but themselves they consider not". Francesco Petrarca understood that nothing is wonderful but the soul, which, when great itself, finds nothing great outside itself. These words also refer to the Augustinian principle of "Noli foras ire, in teipsum redi; in interiore homine habitat veritas" (Do not go out, return to yourself, for the truth dwells in the interior of man) in the De vera religione (39:72). In his De secreto conflictu curarum mearum, Francesco Petrarca would try to reconcile his Renaissance humanism and admiration of the classical world with his Christian faith. In De secreto conflictu curarum mearum he expresses his rejection of love for temporal things not because it is a sin, but because it prevents him from knowing the eternal truth. Francesco Petrarca also regards classical writers as sources of authority supporting Christianity
(see also Francesco Petrarca, the First Modern Man of Letters, Edward Henry Ralph Tatham, Sheldon Press, 1925 and Petrarch's Ascent of Mount Ventoux: The Familiaris IV, I, Francesco Petrarca, Edizioni dell'Ateneo, 2006).

The focus of the Renaissance was on man himself and on the importance of living well in the present (e.g. Renaissance humanism), and this was combined with an explosion of the dissemination of knowledge brought by printing. In the Neoplatonic and Hermetic philosophy of the Renaissance, human beings enjoy unlimited potential, even being capable of becoming gods as was put forward in the Oratio de hominis dignitate: "Poteris in inferiora quae sunt brutav degenerare; poteris in superiora quae sunt divina ex tui animi sententia regenerari. Nascenti homini omnifaria semina et omnigenæ vitæ germina indidit Pater. Quæ quisque excoluerit illa adolescent, et fructus suos ferent in illo. Si vegetalia planta fiet, si sensualia obrutescet, si rationalia cæleste evadet animalb, si intellectualia angelus erit et Dei filius." The great Renaissance adage Magnum, o Asclepi, miraculum est homo can be found found in the Oratio de hominis dignitate of Giovanni Pico della Mirandola (1463-1494 CE). It was this tsunami of new self-confidence that underpinned the sheer intellectual daring that defines the Renaissance. This motto of the Renaissance resembles Psalm 81:6 (Vulgata): "ego dixi dii estis et filii Excelsi omnes" or Psalm 82:6 (Septuagint) ἐγὼ εἶπα θεοί ἐστε καὶ υἱοὶ ὑψίστου πάντες or Hebrew Psalm 82:6 אֲנִי-אָמַרְתִּי, אֱלֹהִים אַתֶּם; וּבְנֵי עֶלְיוֹן כֻּלְּכֶם
(see also The Cambridge Companion to the Italian Renaissance, Michael Wyatt, Cambridge University Press, 2014, p. 265).

The geocentric model of the solar system
according to Aristotle and Claudius Ptolemaeus.

The idea of the Cosmos would change from a geocentric (Ptolemaeic, Aristotelian) model to a heliocentric (Pythagorean, Copernican) model at the end of the Renaissance. The Aristotelian-Thomistic cosmology, which resulted from Thomas Aquinas' rehabilitation and Christianization of Aristotelian cosmology and Ptolemaic astronomy, had dominated (Latin) European thinking from the thirteenth century. The Renaissance world view, as inspired by Aristotle, consisted of three spheres, the lowest consisted of the earth with its four elements symbolized by the Platonic cube. The next level was the celestial world, which consisted of the seven known planets. Finally the supercelestial world consisted of the nine angelic hierarchies, which form into the triangle of the Sacred Trinity. The three worlds were believed to be both present in man (microcosmos) as in the Universe (macrocosmos), which resembled the Hermetic principle 'As above, so below' found in the Hermetic Emerald Tablet. The first known reference to the Emerald Tablet was found in the Kitab sirr al-asrar or Liber secretorum (Book of the science of government: on the good ordering of statecraft) which contains supposed letters from Aristotle (384-322 BCE) to Alexander the Great (356-323 BCE). Both Plato (424/423-348/347 BCE) and Aristotle (384-322 BCE) would be seen in a new light because of the availability of new and better sources directly form Greek sources.

The Latin Aristotelian texts taught in the universities were products of the Middle Ages, most of them translated in the 12^th and early 13^th centuries by Christian scholars who went to Spain and Sicily in order to find the manuscripts and to acquire the linguistic skills they needed. Nearly all of these medieval translations were based not on the Greek originals but on Arabic translations produced in the earlier Middle Ages. Although by the 13^th century nearly all of the Aristotelian works now known had been made available in Latin, those translations were often defective. Renaissance scholars by the 15^th century had become keenly aware of these defects. Once the Italian humanists had learned to read Greek, there was an effort to retranslate Aristotle directly from the Greek and to eliminate the ambiguities and errors of the traditional Latin texts. This push for better translations was led by some of the most influential humanists of the Quattrocento such as Leonardo Bruni (ca. 1370-1444 CE), Ermolao Bárbaro (1453/1454-1493 CE), and Angelo Poliziano. Many new translations were made by emigrant Greek scholars such as George of Trebizond (1395-1472/1473 CE) and Johannes Argyropoulos (1415-1487 CE). At the turn of the 16^th century, the French humanist Jacques Lefèvre d'Étaples (ca. 1455-1536 CE) and several of his followers published new Latin editions of Aristotle for academic use, though many of the translations were the work of Italian and refugee Greek scholars during the preceding hundred years. Renaissance Aristotelianism then produced new directions in the interpretation of Aristotle, in part because of the influence of ancient Greek commentaries that were now becoming available. There was a revival of interest in the interpretation of Aristotle given by the greatest Arabic philosopher of the Middle Ages, Averroes (Ibn Rushd) (1126-1198 CE), who had already been known in the 13^th century, but had aroused much opposition because his interpretation of Aristotle clashed with Christian doctrine. The University of Padua would produce new directions in the interpretation of Aristotle influenced by the works of the famous Arabic philosopher Averroes. The leaders in the 15^th Averroist and Alexandrian revival were three professors at the University of Padua, Nicoletto Vernia (ca. 1420-1499 CE), Agostino Nifo (ca. 1470-1538 CE), and Marcantonio Zimara (ca. 1475-1532 CE). Padua passed under Venetian rule in 1405, and so mostly remained until the fall of the Venetian Republic in 1797 which gave it some independence with regard to matters of faith. The most controversial Averroist philosopher of the early 16^th centry, Pietro Pomponazzi (1462-1525 CE), was striving to reinterpret Aristotle when he wrote his famous treatise On the Immortality of the Soul.

The development of logic in the Renaissance would differ from medieval logic and grammar. Logic had been the instrument of philosophical discourse, while grammar had primarily been used as a similar instrument in theology. Both Lorenzo Valla (1405-1457 CE) and Rodolphus Agricola (1444-1485 CE) would develop a new approach to logic, which was linked with Cicero's Academic skepticism rather than with Aristotelian certainties. They attempted to transform logic into a practical tool measured by persuasiveness and effectiveness.
(see also In Defense of Common Sense: Lorenzo Valla's Humanist Critique of Scholastic Philosophy, Lodi Nauta, Harvard University Press, 2009). Both Valla and Agricola wished to present argumentative strategies for rendering plausible each of the two sides of an undecidable question, or for supporting one of them as, perhaps only marginally, more plausible than the other. Agricola would put forward his views in De inventione dialectica libri tres (1515). With the new interest in persuasive techniques and in discourse as such, logic came to embrace much of what had traditionally been regarded as belonging to rhetoric; and rhetoric came to be seen as concerned not with the invention of topics but with the ornamentation of discourse. Plato would also enter the stage again during the Renaissance as more of his works would become available for the Latin West.

In 1438 George Gemistus Plethon with his lectures on Plato inspired Cosimo de Medici (1389-1464 CE) to found an academy, and in 1462 the Florentine Academy was established when the priest Marsilio Ficino (1433-1499 CE) received the villa of Careggi and its possessions and the Academy would exist until 1522 CE. Marsilio Ficino would write several works on the new philosophy meant to revive Platonism within the Roman Catholic Church and supersede the rigid Aristotelian Scholasticism. His most important works are Theologia Platonica de immortalitate animae on the immortality of the soul (Platonic theology), Commentarium in convivium Platonis de amore on Platonic love or 'amor platonicus', which was a commentary on Plato's Symposion and the De vita libri tres on natural magic as opposed to evil magic (1489). The Ficinian concept of Platonic love means the union of love and spiritual activity in a friendship, which mirrors the love for God, because then the two individuals have attained the highest type of friendship that they can. He also connects the 'amor platonicus' with the 'amor socraticus'. When the spiritual relationship between God and the individual, sought through contemplation, is reproduced in a friendship or love with another person, that constitutes for Ficino spiritual or Platonic love
(see also Platonicus amor: Lesarten der Liebe bei Platon, Plotin und Ficino, A. Wurm, Walter de Gruyter, 2008 and Dictionary of Literary Terms and Literary Theory, J. A. Cuddon, John Wiley & Sons, 2012, p. 810 and Renaissance Theory of Love: The Context of Giordano Bruno's Eroici Furori, J. C. Nelson, Columbia University Press, 1958). The central doctrine of his Neoplatonic philosophy is that the human soul is immortal and the center of the universe, just like the 'anima mundi'. The human soul is the only thing that sits inbetween the abstract realm of ideas (intellect, Nous) and the physical world-as such, it is the mediator between these two worlds. For Ficino the central position of the human soul in the universe made humanity the most dignified of all objects in God's creation. Ficino as a Neoplatonist believed that the purpose of human life was contemplation as a means to reach the ultimate goal of human life, which was to be reunited with God, at least in an intellectual or spiritual sense.
(see also Renaissance Neo-Platonism, R. Hooker, Washington State University, 1997).

Important members of the Academy were Angelo Ambrogini a.k.a. Politian (or Poliziano) (1454-1494 CE), Cristoforo Landino (1424-1498 CE), Giovanni Pico della Mirandola (1463-1494 CE), and Gentile de' Becchi (1420/30-1497 CE). Members of the academy would proceed to translate into Latin all of Plato's works, the Enneads of Plotinus, and various other Neoplatonic works such as the Corpus Hermeticum. Scholars such as Giovanni Pico della Mirandola (1463-1494), Marsilio Ficino (1433-1499 CE) would play an important role in the revival of Plato and Neoplatonism in (Latin) Western Europe during the Italian Renaissance. Poggio Bracciolini (1380-1459 CE) in an abbey in southern Germany in 1417 rediscovered the poem De Rerum Natura of Lucretius which would introduce Epicurean ideas and atomism to Renaissance philosophy. The poem would also inspire Sandro Botticelli (ca. 1445-1510 CE) for his painting the Primavera (1482 CE).

The Neoplatonists of the Renaissance sought to combine Platonism with Hermeticism and Christian Cabala and thereby reforming Christian philosophy by liberating it from rigid Aristotelian Scholasticism. Cardinal Bessarion (1403-1472 CE), Nicolaus Cusanus (1401-1464 CE), Marsilio Ficino (1433-1499 CE), and Pico della Mirandola (1463-1494 CE) can be considered to be the leading Italian Renaissance Neoplatonists. Marsilio Ficino introduced Platonism and Hermeticism, while Pico della Mirandola added Christian Cabala into Renaissance Christianity. Ficino translated the Corpus Hermeticum into Latin, which caused a philosophical and theological renewal. Early Christian authors Lactantius (ca. 240-ca. 320) and Aurelius Augustinus (354-430 CE) had already written about Hermes in the third and fourth centuries CE, respectively. Lactantius, who occasionally quotes sections of the Corpus Hermeticum (Divinarum Institutionum Libri VII, I.vi, De ira Dei, XI), claims in his De ira Dei that Hermes is considerably more ancient than both Plato and Pythagoras, and Augustine even places him shortly after the time of Moses, yet simultaneously far earlier than the Greek philosophers. Lactantius regarded Hermes Trismegistus as one of the most important of the Gentile seers and prophets who foresaw the coming of Christianity, because he spoke of the Son of God and the Word
(see also Giordano Bruno and the Hermetic Tradition, Francis A. Yates, The University of Chicago Press and London: Routledge and Kegan Paul, 1964). Due to the writings of Lactantius and Augustine, the Corpus Hermeticum was considered to be of great antiquity and represent the 'prisca theologia', the primordial theology revealed by God.
(see also The Egyptian Hermes: A Historical Approach to the Late Pagan Mind, G. Fowden, G. Princeton University Press, 1993 and Neoplatonism in science: Past and future, B. Maclennan, University Press of the South, 2007 and Hermetica: The Greek Corpus Hermeticum and the Latin Asclepius in a New English Translation, with Notes and Introduction, B. P. Copenhaver (Editor), Cambridge University Press, 1992).

The connection with Hermeticism and Christian Kabbalah, was expanded upon by authors based upon the early work of Pico. Pico della Mirandola roused the ire of the papacy by composing a voluminous work Conclusiones sive Theses DCCCC defending nine-hundred theses drawn from his vast reading of the Ancients. Pico wanted to create a new philosophy, which would overcome the contradictions between the different streams of though which prevailed in his time. Three basic elements were part of his 'philosophia nova': cosmic emanationism, cosmic proportions and correspondences and conversion. According to Pico, God did not create the universe directly, but acted through a series of intermediaries. This view was based on the hierarchical view on the universe of Proclus's Platonic theology. Emanationism had been opposed by Thomas Aquinas (1225-1274 CE) the founder of Thomism. Pico put forward a highly correlative system of the cosmos, in which everything stanging on one level of reality reappeared in some mode on every other level. The principle "omni sunt in omnibus modo suo" (all things exist in all things in their own mode) was also the central principle of late Neoplatonism. Ascending up the hierarchy of being is accompanied by an increase in the perfection of individual properties and by their progressive reciprocal penetration ('ad invicem penetratio'). The cosmic ascent and descent is expressed in mathematical terms as a movement between unity and multiplicity. Finally Pico wanted to overcome the ontological problem of "being" and the "one". He had dealt with this issue in De Ente et Uno (1491) and the Concord of Plato and Aristotle. The central problem is whether being or the one is ontologically prior to the other or which one is simpler and therefore more universal. Neoplatonists in their intepretation of Plato's Parmenides (370 BCE) put forward that the one was superior to being. This is also what distinguishes Western-Indian philosophy from Chinese philosophy, where Chinese philosophy puts being first. Western-Indian philosophy philosophy aspires unchanging unity, while Chinese philosophy accepts change as fundamental. The Neoplatonic view was developed at length by Proclus in his Platonic Theology. Pico however rejected this for the view of correspondence of being and the one as an attempt to reconcile Plato with Aristotle. For Pico being and the one correspond with each other and can be converted into each other. These principles are coextensive and are in fact identical principles. The result of Pico's attempt was a complete correlatieve ontology which harmonized all in a hierarchical and correlated unity of being. Thirteen of the theses from the Conclusiones sive Theses DCCCC were deemed heretical by the pope Innocent VIII (1432-1492 CE). Pico as a response wrote the unsubmissive Apology. The introduction to the Conclusiones sive Theses DCCCC came to be known as the Oratio de hominis dignitate, which he had written in 1486 to introduce his 900 Conclusions. The Oratio de hominis dignitate (1486) by Pico della Mirandola can be considered to be the central Manifesto of the Renaissance and emphasized the human freedom and capacity to know and to dominate reality as a whole. In this work he described Man's (Neoplatonic) Ascent to the Divine in three stages: the first step is through 'Purification' (Nothing too much), the second step is through 'Contemplation' (Know thyself) and finally Man reaches the 'Union' with the Divine (Thou art). Renaissance philosophers put forwared the pursuit of man towards its destiny begins with moral self-discipline, passes through the familiar world of images and fields of knowledge, and strives toward its goal which defies representation
(see also On the Dignity of Man, Giovanni Pico della Mirandola, Hackett Publishing, 1998). The process resembles the Neoplatonic ascent to 'The One' or Henosis of Plotinus (ca. 204/5-270) and the mystical theology of Pseudo-Dionysius the Areopagite (late 5^th to early 6^th century)
(see also Syncretism in the West, Stephen Alan Farmer, Medieval & Renaissance Texts & Studies, 1998).

The Oratio de hominis dignitate stood in a tradition of philosophical thought on the human condition. The theme of the dignity of man had an equally developed counter-theme of the misery of man
(see also Two Contrasting Renaissance Visions of Man, Timothy G. Enloe). Decimus Iunius Iuvenalis (late 1^st and early 2^nd century CE) already warned of the transience of wealth, power, beauty, children, long life, and other temporal goods, and noted that in a world of suffering a man's best hope is to tread the path of virtue. The Renaissance discussion on the human condition dated back to pope Innocent III (1160 or 1161-1216 CE), who wrote his De miseria humanae conditionis (On the Misery of Human Condition) which should be followed by the other more positive view, which was never published
(see also The Darker Vision of the Renaissance: Beyond the Fields of Reason, Robert S. Kinsman, University of California Press, 1974, p. 56). Petrarch as a response on De miseria humanae conditionis wrote his Remediis Utriusque Fortune (Remedies for Fortune Fair and Foul)
(see also Petrarch's Remedies for Fortune Fair and Foul. by Petrarch, Conrad H. Rawski, Robert E. Proctor, Speculum, Vol. 69, No. 2 (Apr., 1994), pp. 547-549). This was followed by De excellentia ac praestantia hominis (Of the excellences and outstanding character of Man) of Bartholomaus Facius (ca. 1400-1457 CE) and De dignitate et excellentia hominis of Giannozzo Manetti (1396-1459 CE). The view of the Oratio de hominis dignitate would be followed by Juan Luis Vives (1493-1540 CE) who wrote his Fabula de homine (A Fable about Man, 1518). The more pessimistic view on the human condition of Innocent III can be found in the work of Gian Francesco Poggio Bracciolini (1380-1459 CE), who wrote De miseria humanae conditionis (On the Misery of Human Life, 1455) as reflections during his retirement in Florence inspired by the sack of Constantinople. Giovanni Garzoni (1419-1506 CE) wrote the pessimistic De miseria mundi libellus. Michel de Montaigne (1533-1592 CE) wrote his Apology for Raymond Sebond (1576 CE) in which he dealt with the human condition. Montaigne in his essay expressed great admiration for the Pyrrhonists, the followers of Pyrrho (ca. 360-ca. 270 BCE), and their ability to maintain the freedom of their judgment by avoiding commitment to any particular theoretical position. In his Apology for Raymond Sebond Montaigne also argues that physical weakness, feeble reason, and thwarted yearning for temporal hapiness all mock the notion of human excellence. Pierre Charron (1541-1603 CE), a disciple and contemporary of Michel Montaigne, wrote De la Sagesse Livres Trois in which he developed a system of moral philosophy based on the ideas of Montaigne. Here Pierre Charron also connected Montaigne's scepticism with the anti-rational strand in Christianity
(see also The Columbia History of Western Philosophy, Richard H. Popkin, Stephen F. Brown, David Carr, Columbia University Press, 2013, pp. 298-299).

The Venetian Franciscan friar, Francesco Giorgi Veneto (1466-1540 CE) published his De harmonia mundi totius in 1525 and the In Scripturam Sacram Problemata in 1536. Francesco Giorgi integrated Pythagorean numerology with Platonism and Vitruvian architecture, and connected these with the geometry of the Temple of Solomon. 'De harmonia mundi totius' was believed to present the plan from which the Architect of the Universe worked, and like the Temple of Solomon, its meaning could supposedly be understood by those who knew how to Pythagorise and philosophise by mathematics. According to Francesco Giorgi Veneto both the 'via Platonicorum' and the 'via Aristotelica' lead to Divine knowledge, but while Aristotle starts at the bottom of the spiritual ladder in the world of the four elements, Plato and the Pythagoreans begin with number and mathematics (Mathesis Universalis) which provides them with an easier way in their (Hermetic) ascend though the spheres.

The heliocentric model of the solar system
according to the Pythagorean Aristarchos of Samos and Nicolaus Copernicus.

In Poland, Nicolaus Copernicus (1473-1543 CE) published his De revolutionibus orbium coelestium on the Heliocentric system in 1543. This non-homocentric but heliocentric view of the universe would lead to new philosophical and theological developments
(see also Morphometrics for the Life Sciences, P. E. Lestrel, World Scientific, 2000, p. 64 and Fire Within the Universe, E. Varini, Janus Publishing Company Lim, 2002, p. 39). The Italian Dominican friar Giordano Bruno (1548-1600 CE) with his heretic Egyptian, Neoplatonic, Hermetic "Prisca Theologia", was burned alive at the stake on 17 February 1600 in the Campo de' Fiori in Rome for his heresies as his theology conflicted with the Roman Catholic Bible and the Aristotelian (Thomistic) doctrine of the Roman Catholic Church. Giordano Bruno (1548-1600 CE) had written extensively about a new philosophy meant to revitalize Roman Catholicism and which was inspired by Neoplatonism, Hermeticism and Pantheism. He was also in support of Epicurean atomic theory
(see also The Scientific Revolution, W. E. Burns, ABC-CLIO, 2001, p. 25). Accepting atomism and the void which came with it, lead him to postulate the infinity of the universe. Giordano Bruno introduced elements of Platonic idealism into atomic theory, and expanded the traditional definition of the atom, adding specific spiritual attributes, such as the possession of a soul, in an effort to reconcile a corpuscular theory of matter with his grand vision of an essentially spiritual universe
(see also Late Medieval and Early Modern Corpuscular Matter Theories, C. H. Lüthy, J. E. Murdoch, W. R. Newman, BRILL, 2001, p. 175 and The Wholeness of Nature, H. Bortoft, Steiner Books, Part III, p. 3 and The World Perceived, A. J. MacDonald, A. J. MacDonald, Jr., 2009, p. 68). Bruno believed that Hermeticism represented the true religion, the wisdom of ancient Egypt that had been corrupted, first by the Jews and then the Christians. His works include the La Cena de le Ceneri (1584 CE), De la Causa, Principio et Uno (1584), Spaccio de la Bestia Trionfante (1584 CE), De l'infinito universo e mondi (1584 CE) and Articuli centum et sexaginta adversus huius tempestatis mathematicos atque Philosophos (1588 CE). In De la Causa, Principio et Uno Bruno put forward his Neoplatonic panpsychist view
(see also Giordano Bruno: Cause, Principle and Unity, G. Bruno, Cambridge University Press, 1998). Bruno believed that the same principles must apply throughout the cosmos; the Earth held no privileged position in the universe (such as being at the center), and humans held no privilege with respect to possessing a soul. He took the Platonic world-soul (anima mundi) and the human soul as given, and concluded that all things, all parts of the whole, must be animated. Bruno presented his 120 theses against Aristotelian natural science at the University of Paris in 1585, which soon put him in ill favor. Bruno in the Cena de le ceneri (The Ash Wednesday Supper), advocated Copernicus and declared that establishing heliocentricity would free the human spirit. Arguing for the physical reality of the infinite universe with no centre, yet whose centre is everywhere, Bruno sought to prove that each man is every other man. Using this radical cosmology and the imagery of Lenten regeneration, the messianic Bruno sought to heal the secular and religious wounds of sixteenth-century Europe by reconciling Catholic and Protestant, France and England (La Cena de Le Ceneri, G. Bruno, University of Toronto Press, 1995 and Giordano Bruno: His Life, Thought, and Martyrdom, W. Boulting, Routledge, 2013 and Giordano Bruno and the Hermetic tradition, F. A. Yates, University of Chicago Press, 1991)

Together with Ramon Llull (ca. 1232-ca. 1315 CE) and Giullo Camillo (ca. 1480-1544 CE) Bruno developed the classical Ars Memorativa (E: Art of Memory). They mixed visual and verbal media. Their pictures contained visual puns ('memoria artificiosa'), words were often verbal paintings, and both were used equally as tools for making thoughts. The ability to create pictures in one's own mind was essential to cognitive technique and imagination, and the intensely pictorial and affective qualities of their art and literature were generative, creative devices in themselves. They built memory theatres that were appallingly complex, based on 'loci' and 'imagines agentes'. They were supposed to hold information about every aspect of the universe - the entire history of human civilization. The theatre represented the cosmos, and the images inside it, knowledge of the cosmos. The highest aspiration of these Artists of Memory was gnosis - divine knowledge and universal memory. They believed they could produce a kind of information system capturing all the knowledge in the universe located within the human mind and ultimately lead to the transformation of man to reach the intelligible world beyond appearances
(see also The Art Of Memory, F. A. Yates, Random House, 2011 and The Medieval Craft of Memory, M. J. Carruthers, J. M. Ziolkowski, University of Pennsylvania Press, 2004 and Sprichwortbild und Sprichwortschwank, Andreas Bässler, Walter de Gruyter, 2003).

The Dominican Tommaso Campanella (1568-1639 CE) would follow in Bruno's footsteps. His most important works are Philosophia realis, De sensu rerum and of Atheismus triumphatus, Philosophia rationalis and the Metaphysica. His heterodox views, especially his opposition to the authority of Aristotle, brought him into conflict with the ecclesiastical authorities. Campanella's new natural philosophy rested on the principle that the books written by men needed to be compared with God's infinite Book of Nature, allowing them to correct the mistakes scattered throughout the human copies which were always imperfect, partial and liable to revisions. It is in the light of these principles that he defended Galileo's right to read the Book of Nature while denouncing the mistake of those be they Aristotelian philosophers or theologians who wanted to stop him from carrying on his natural investigations
(see also Tommaso Campanella: The Book and the Body of Nature, G. Ernst, Springer, 2010). His most famous work was La città del Sole (The City of the Sun), which was inspired by Plato's The Republic (380 BCE) and the description of Atlantis in Timaeus, and where he describes a theocratic society. For Campanella nature as a whole was an organism in which each single part was directed towards the common good. This is the reason why Campanella thought that nature had to be regarded as an ideal model for any political organisation. Campanella's philosophical system centered on his doctrine of the "three primalities" (primalitates): power, wisdom, and love, which he explained in his Metaphysica. God, the first infinite cause, has his essence in the principles of Power, Wisdom and Love in an infinite manner. Every finite being is composed of these same primalities but in ways and proportions that are limited and differentiated. After the explanation of the doctrine of the primalities comes that of the three great influences: Necessity, Fate and Harmony, the vehicles by which the divine Idea, in all its infinite degrees, is conveyed to the world and to matter (Nature)
(see also Tommaso Campanella; Renaissance pioneer of modern thought, B. M. Bonansea, Catholic University of America Press, 1969 and Spiritual & Demonic Magic from Ficino to Campanella, D.P. Walker, Studies of the Warburg Institute, Vol. 22, 1958 and Witch Hunting, Magic and the New Philosophy: An Introduction to Debates of the Scientific Revolution 1450-1750, B. Easla, Humanities Press, Inc., 1980).

Figurae Mentis nota (Father, Sun), Figurae Intellectus (Son, Moon),
Figurae Amoris (Spirit, anima mundi, spiritus universorum, Light, fulgor, Star) as the Hermetic Trinity
pater, mens; filium verbum; et per verbum, universa sunt producta
- Giordano Bruno, Lampas triginta statuarum -

After 1500, the Renaissance spread to northern Europe, where it became closely linked to the Protestant Reformation. In England, Thomas More (1478-1535 CE) and the mathematician John Dee (1527-1609 CE) played an important role in the English Renaissance. John Dee notably with The Mathematicall Praeface to Elements of Geometrie of Euclid of Megara of Henry Billingsley's (d. 1606 CE) English translation of Euclid's Elements in 1570: The elements of geometrie of the most ancient philosopher Euclide of Megara
(see also John Dee's Natural Philosophy, N. Clulee, Routledge, 2013). In the Netherlands, the humanism of Desiderius Erasmus of Rotterdam (1466-1536 CE) played an important role in the Northern Renaissance and he came to be known as the Prince of the Humanists. Using humanist techniques for working on texts, Erasmus prepared important new Latin and Greek editions of the New Testament. These raised questions that would be influential in the Protestant Reformation and Catholic Counter-Reformation. Erasmus also wrote the Stultitiae Laus (1509 CE) (The Praise of Folly) which is considered one of the most notable works of the Renaissance and one of the catalysts of the Protestant Reformation. In On the Freedom of the Will (1524) and the Stultitiae Laus, Erasmus attempts to show that skepticism and Christianity are not mutually exclusive ideologies. His simultaneous dedication to faith and dedication to skepticism synthesize into a mitigated skepticism that argues for the suspension of judgement. Erasmus's augmented skepticism allows for knowledge by faith, and so satisfies the criterion for being Christian, but struggles to remain skepticism. In December of 1525, Martin Luther (1483-1546 CE) responded to Erasmus with The Bondage of the Will. In Germany Martin Luther (1483-1546 CE) the Protestant reformer, Konrad Celtis (1459-1508 CE), Johann Reuchlin (1455-1522 CE), the printer Johannes Gutenberg (c. 1398-1468 CE) and Albrecht Dürer (1471-1528 CE) were the leading figures of the northern Renaissance. The humanist scholar of Greek and Hebrew Johann Reuchlin, probably wrote the Epistolæ Obscurorum Virorum (1515-1519 CE) (E: Letters of Obscure Men) which gave "obscurantism" its name. The obscurant favors restricting knowledge (publication, extension, dissemination) among the populace, for the "greater good" of the nation or church. Any (philosophical) system which claims to be complete with regard to reality, leads to "obscurantism" and scepticism due to its complexity and the resulting vagueness. Systems which do not claim completeness, with regard to reality, can be comprehended within the philosophical system itself.

With regard to the development of Renaissance logic Philipp Melanchthon (1497-1560 CE) would be influenced by Rodolphus Agricola (1444-1485 CE) and his De inventione dialectica libri tres. Melanchton would write the Compendiaria dialectices ratio and Erotemata dialectices (1547) with influences of Cicero and Quintilian. Petrus Ramus (1515-1572 CE), who was also influenced by Rodolphus Agricola, would write his Dialectique (1555) or Dialecticae libri duo (1556). The Dialectique had two parts. The first, on invention, covered the Topics The second part, on judgment, presented a deliberately simplified version of the syllogism followed by an account of method as a means of ordering in the arts and sciences. The Philippo-Ramist school would develop out of their work, combining the strengths of their approach to logic. As part of the Counter-Reformation, the Jesuits Francisco de Toledo (1533-1596 CE) and Pedro de Fonseca (1528-1599 CE), a member of the Collegium Conimbricenses, would publish the Introductio in dialecticam (de Toledo, 1561) and Institutionum dialecticarum (de Fonseca, 1564) in which they presented a standard Aristotelian logic.

Justus Lipsius (1547-1606 CE) was the founding father of Neostoicism. He worked in Lovain and in Leiden, where he published his De Constantia Libri Duo, Qui alloquium praecipue continent in Publicis malis (1583/4 CE) (De Constantia I and De Constantia II) and the Politicorum sive Civilis doctrinae libri sex (1589). In De constantia Lipsius brought forward Seneca's (ca. 1 BCE-65 CE) stoic philosophy both as a consolation and a solution to the public calamities which he and his contemporaries were enduring. In the Politica Lipsius put forward the principle that the ruler had to apply reason and political virtue to government, but first of all to his own life. The Politica was concerned with the construction of civil life and the state in an ethical context. Besides using antique, medieval and renaissance sources, Lipsius applied the principles of Ramist logic, based on the work of Petrus Ramus (1515-1572 CE). On stoicism Lipsius published his Manuductionis ad Stoicam philosophiam libri tres (1602) and Physiologiae Stoicorum libri tres (1602). Central to Lipsius's insight into Stoic philosophy was his perception that its ethics and physics were inseparable: it was not possible to live one's life in accordance with nature, as Stoic ethics demanded, without a full knowledge of the physical workings of nature. Guillaume Du Vair (1556-1621 CE), a Neostoicist and admirer of Lipsius, drew his inspiration mainly from the stoic Epictetus (55-135 CE). His most important works on stoicism are De la constance et consolation ès calamités publiques (1589) and Philosophie morale de Stoïques. Du Vair tried to combine Christianity with his admiration for stoicism and Epictetus.

Renaissance scholars not only studied ancient Greek philosophy but also tried to find the very origins of human civilization, the so-called "prisca theologia" (ancient theology), such as the Hermetic texts from ancient Egypt, the Chaldaean Oracles and writings of Zoroaster from Mesopotamia and Persia, the teachings attributed to Pythagoras (ca. 570-ca. 495 BCE) and supposedly passed on from him to Plato and his followers the Platonists, and the secret Jewish books known as Cabala, which claimed to present the full meaning of the Hebrew Scriptures concealed beneath the words of the text. During the rise of Protestantism a Roman Catholic Counter-Reformation would form against the philosophers of the Renaissance, which were held (partly) responsible for the emergence of the competing Christian theology. Jean Bodin (1530-1596 CE), one of the major political theorists of the sixteenth century, would publish his De la démonomanie des sorciers (1580) in which he condemned Pico as a wicked magician, together with Heinrich Cornelius Agrippa von Nettesheim (1486-1535 CE) who had written De occulta philosophia libri tres and who became the prototype of the black magician. Rudolphus Goclenius (1547-1628 CE) in 1604 would publish his Controversia logicae et philosophiae, ad praxin logicam directae, quibus praemissa sunt theoremata seu praecepta logica in which he summarized the philosophical controversies of his time, such as the controversy with regard to universals between realists and nominalists. In his Problemata logica (1590), he also developed the Goclenian Sorites or little-by-little arguments, a specific kind of polysyllogism. Sorites may lead to the Sorites Paradox.

Due to this association with Neoplatonism, Hermeticism and Christian Cabala, Renaissance philosophers were being placed on the Index Librorum Prohibitorum during the Roman Catholic Counter-Reformation, beginning with the Council of Trent (1545-1563) and ending at the close of the Thirty Years' War (1618-1648 CE). The Index Librorum Prohibitorum is a classical example of obscurantism. The obscurant (the Roman Catholic Church) favors restricting knowledge (publication, extension, dissemination) among the populace, for the "greater good" of the Roman Catholic Church. The Council of Trent gave the definitive answer of the Roman Catholic Church to the Protestant demand for a thorough reformation of the Church. The Protestants had put forth the five great themes of sola scriptura, sola fide, solus Christus, sola gratia, and soli Deo Gloria. The Council decreed that both Scripture and tradition were to be of equal authority in order to save the Aristotelian basis of its theology. The Council of Trent also reiterated the Roman Catholic Church's sole authority to interpret the Scriptures. Trent also upheld the validity of the seven sacraments. The Protestant doctrine of sola fide or by faith alone was decisively spurned by the canons of Trent respecting justification. The works of Desiderius Erasmus were to be placed on the Index Librorum Prohibitorum of forbidden books. The Renaissaince was condemned as a social and religious programme of radical Reform, which had tried to bring "Egyptianism" to the core of a New Europe.

Vitruvian man by Leonardo da Vinci after Vitruvius, The Ten Books on Architecture
Book III, Ch. I On symmetry: in temples and in the human body

Renaissance
Byzantines in Renaissance Italy
Philosophia perennis
History of the Warfare of Science with Theology in Christendom
Dante Alighieri - (1265-1321 CE)
Dante Alighieri - (1265-1321 CE)
Works by Dante Alighieri - Dante
Nicholas Cusanus
George Gemistos Plethon - (1355-1452 CE)
George of Trebizond - (1395-1484 CE)
Johannes Cardinal Bessarion - (1403-1472 CE)
Biblioteca Nazionale Marciana
Leone Battista Alberti - (1404-1472 CE)
Hypnerotomachia Poliphili - Leon Battista Alberti
Marsilio Ficino - (1433-1499 CE)
De Sole - Marsilio Ficino
Platonica Theologia de immortalitate animorum - Marsilio Ficino
Johann Reuchlin - (1455-1522)
Giovanni Pico della Mirandola - (1463-1493 CE)
Oratio de hominis dignitate (Oration On the Dignity Of Man) - della Mirandola
Pico Project
Desiderius Erasmus - (1466-1536 CE)
The Praise of Folly - Erasmus
Erasmus Centre
Thomas More - (1478-1535 CE)
Utopia - Thomas More
Justus Lipsius - (1547-1606 CE)
Hugo Grotius - (1583-1645 CE)
Hugo Grotius - (1583-1645 CE)
De Jure Belli ac Pacis - Hugo Grotius

The dawn of modern science would cause a crisis in traditional religion, philosophy and morality. In the sixteenth and seventeenth centuries there was a radical change in the 'medieval worldview' or 'paradigm', which had survived into the Renaissance. Loss of the 'a priori' truth of traditional philosophy destroyed the bridge from subject to object. The notion of an organic, living and spiritual universe was replaced by that of the world as a machine. The medieval link between the divine world-order and human reason was broken. No longer there was a divine relation between the perceived world and man's understanding of the world. The solution would either be the primacy of experience (empiricism) or the primacy of man's reason (rationalism). The result would either lead to the solipsism of René Descartes (1596–1650 CE) or the skepticism of David Hume (1711–1776 CE)
(see also The Big Questions: A Short Introduction to Philosophy, Robert C. Solomon, Kathleen M. Higgins, Cengage Learning, 2009, p. 151).

The dawn of modern science and philosophy also meant the demise of the organic and magical world view of the Renaissance. When Isaac Casaubon (1559-1614 CE) in his analysis of the Corpus Hermeticum dated the Hermetic writings as a post Christ collection of Greek writings, this marked the demise of Renaissance Hermeticism and Neoplatonism. Due to the work of scholars like Isaac Casaubon (1559-1614 CE) and Marin Mersenne (1588-1648 CE), of the Roman Catholic order of Minims, philosophy and science got rid of their Renaissance Hermeticism and Magic. Marin Mersenne saw very dangerous consequences flowing from the Renaissance revival of the Platonic doctrine of the anima mundi, or world soul-the notion that matter was imbued with life and the associated identification of God with nature. Mersenne developed a view of matter as completely passive and inert. This view was not invented during the Renaissance but existed as a powerful tradition among the Presocratic Ionians as well as among later Epicureans. The world-machine as it was revived by Mersenne, was designed to banish multifarious popular deities and intelligences, along with the authority of obsolete Scholastic texts from the post-Renaissance European imagination, leaving all spiritual power in the hands of a single transcendent Biblical God, utterly removed from human manipulation. By restricting the territory of the soul in the material world to man alone and denying it to any part of nature, however, the world-machine paradigm removed the only mechanism by which God had heretofore been understood to operate upon the world in any capacity but as a function of man's intellect. In Quaestiones celeberrimae in Genesim (1623) Mersenne opposes magical and divinatory arts, cabalism, animistic and pantheistic philosophies. Mersenne condemns astral magic and astrology and the anima mundi, a concept popular amongst Renaissance neo-platonists. He also criticises Giovanni Pico della Mirandola (1463-1494 CE), Cornelius Agrippa (1486-1535 CE) and Francesco Giorgio (1466-1540 CE) with Robert Fludd (1574-1637 CE), the Paracelsian and Rosicrucian, as his main target. Mersenne's view was elaborated by his friend René Descartes (1596-1650 CE) in his natural philosophy. The idea of a purely mechanical universe of passive matter was reasserted during the 17^th century in support of monotheism, while the world-soul as a principle manifestly present in the natural world, by "blurring the distinction between natural and supernatural", tended to appeal to popular atheistic (or neo-pagan) tendencies. By advancing the world-machine paradigm, the "distinctions between what was natural and what was supernatural could be maintained". After Mersenne's world-machine was taken to its logical limits by Descartes, however, a reaction against mechanicalism was offered not by atheists but by the Christian Neoplatonists of the Cambridge school. In addition to popular pantheism, and Cambridge Platonism, University scholasticism was placed into opposition with the mechanical universe paradigm. Scholasticism had undergone continuous attack from humanist factions throughout the Renaissance, and by the 17^th, strict Aristotelianism was already on its way out of the European University
(see also The Rosicrucian Enlightenment, Frances Yates, Routledge, 2003, p. 148 and Giordano Bruno and the Hermetic Tradition, Frances A. Yates, Routledge, 2014, p. 439 and The Mechanization of Natural Philosophy, Sophie Roux, Springer Science & Business Media, 2012).

The early modern era of Western philosophy is usually identified with the 17^th and 18^th centuries, with the 18^th century often being referred to as the Enlightenment. The development of new ideas during the Renaissance about nature, man, science and religion made it necessary to develop a new synthesis. Medieval philosophy had stated that faith and reason could not contradict one another: faith and reason co-operated to depict a world in which everything accorded with the divine purpose. During the Renaissance this medieval synthesis collapsed due to the developments in natural philosophy which undermined the synthesis between Aristotelian science and faith. Modern Western philosophy would distinguish itself from its predecessors by its increasing independence from traditional authorities such as the (Roman Catholic) Church and academia, both still Aristotelian institutes. A new focus on the foundations of knowledge and metaphysical system-building started together with the emergence of modern physics out of natural philosophy. Other central topics of philosophy in this period include the nature of the mind and its relation to the body, the implications of the new natural sciences for traditional theological topics such as free will and God, and the emergence of a secular basis for moral and political philosophy. These trends first distinctively coalesce in Francis Bacon's (1561-1626 CE) call for a new, empirical program for expanding knowledge, and soon found massively influential form in the mechanical physics and rationalist metaphysics of René Descartes (1596-1650 CE). Descartes was a major figure in 17^th-century continental rationalism, later advocated by Baruch Spinoza (1632-1677 CE) and Gottfried Wilhelm Leibniz (1646-1716 CE), and opposed by the British empiricist school of thought consisting of Thomas Hobbes (1588-1679 CE), John Locke (1632-1704 CE) (the father of Liberalism), Bishop George Berkeley (1685-1753 CE) and David Hume (1711-1776 CE). Immanuel Kant (1724-1804 CE) would bring together the strands of thought of these two schools and founded a new philosophical orientation marking the beginning of what is often called the "Late Modern Period". Concerning universals, the rationalists would stand in the realist tradition ('in res'), while the empiricists would stand in the nominalist tradition ('post res'). The approximate end of the early modern period is most often identified with Immanuel Kant's systematic attempt to limit metaphysics, justify scientific knowledge, and reconcile both of these with morality and freedom
(see also Philosophical Theories, Morris Lazerowitz, Alice Ambrose, Walter de Gruyter, 1976, p. 185 and Modern Philosophy: From 1500 CE to the Present, Brian Duignan, The Rosen Publishing Group, 2011, p. 75).

Besides the British empiricists, the French Sensationalists (French Newtonians of the mind) and the Positivists would also respond to the rationalism of René Descartes. The French Sensationalists, such as Pierre Gassendi (1592-1655 CE), Julien Offray de La Mettrie (1709-1751 CE), Étienne Bonnot de Condillac (1715-1780 CE) and Claude Adrien Helvétius (1715-1771 CE) were materialists who rejected René Descartes' rationalism. Sensationalism is a form of Empiricism that limits experience as a source of knowledge to sensation or sense perceptions. It is also a consequence of the notion of the mind as a 'tabula rasa', or 'blank slate'. Its most extreme form was fund in the 'sensationnisme' of Étienne Bonnot de Condillac. The Positivists, such as Auguste Comte (1798-1857 CE) and Ernst Mach (1838-1916 CE) denied innate ideas and believed that science can only study that which can be observed. For Auguste Comte there were three stages of human development, the 'theological' (pre-Enlightenment), the 'metaphysical' (Enlightenment unitl after the French revolution), and finally the 'positive' or scientific stage. These ideas he put forward in Discours sur l'ensemble du positivisme (1848) and which he called 'La loi des trois états' (E: Law of Three Stages)
(see also An Introduction to the History of Psychology, B. R. Hergenhahn, Tracy Henley, Cengage Learning, 2013, p. 152).

The new confidence in human reason would also lead to a new relation with antiquity. In the early 1690s there was the Querelle des Anciens et des Modernes in France. The Querelle in France erupted in early 1687, when Charles Perrault (1628-1703 CE) read his poem Le Siècle de Louis le Grand (1687 CE) at a meeting of the Académie française. On one side the "Anciens" supported the merits of the ancient authors, and contended that a writer could do no better than imitate them. The Ancients viewed Greco-Roman civilization as the apex of human achievement and all subsequent culture as a decline from this high point. On the other side were the "Modernes" which supported the merits of the authors of the century of Louis XIV. The Moderns saw human knowledge and understanding as progressing since antiquity. The "Modernes" supported the idea of Progress and the "Anciens" supported Authority. In the end superiority in science was granted to the "Modernes" and superiority in arts was ceded to the "Anciens". The attack on authority in literary criticism had analogues in the rise of scientific inquiry, and the challenge of the "Modernes" to authority in literature foreshadowed the challenging inquiry in systems of politics and religion. In England this would become the satire Battle of the Books by Jonathan Swift (1667-1745 CE) and William Temple's (1628-1699) Of Ancient and Modern Learning (1690)
(see also The Classical Tradition, Anthony Grafton, Glenn W Most, Salvatore Settis, Harvard University Press, 2010, p. 44 and The Battle of the Books: History and Literature in the Augustan Age, Joseph M. Levine, Cornell University Press, 1991, p. 116).

Rationalists postulate that there is a complete, and completely rational, explanation for everything which occurs. Their conception of reason is that knowledge (or truth) is arranged in a deductive system, and that one must start with self-evident a priori truths of which we can be certain (first principle). The Rationalists did not believe that our sensory experience could provide us with reliable knowledge of the world. Instead, the Continental Rationalists held that it is only via a priori intellectual perceptions that man is capapble of capturing the fundamental nature of the universe. The appropriate methodology for building upon the self-evident truths is the deductive axiomatic method of mathematics wherein theorems are derived from axioms and postulates. The truth of the theorems is of course dependent upon the truth of these axioms and postulates. The Rationalists had an unrelenting faith in the capacity of human reason and they held that man could arrive at knowledge unaided by religious faith or revelation
(see also The Rationalists: Descartes: Discourse on Method & Meditations; Spinoza: Ethics; Leibniz: Monadolo gy & Discourse on Metaphysics, Rene Descartes, Benedict de Spinoza, Gottfried Wilhelm Von Leibniz, Knopf Doubleday Publishing Group, 2011 and A Companion to Rationalism, Alan Nelson, John Wiley & Sons, 2012).

- René Descartes - Discours de la Méthode pour bien conduire sa raison, et chercher la vérité dans les sciences -

René Descartes (1596-1650 CE) rejected the Medieval synthesis which had dominated Western thought for more than 400 years since Thomas Aquinas (1225-1274 CE), and which was based on the philosophy of Aristotle (384-322 BCE). Descartes aspired to rebuild a new system of truth based upon an unquestionable first principle. He attempted to solve the problem of determinism which was caused by the mathematical world-view. By introducing a dualist world-view, which distinguishes between matter (res extensa) and soul (res cogitans), he made an attempt to free man (human soul) form the determinism of mathematical physics. René Descartes based his philosophy on the principles of Academic (Platonic) skepticism in which became known as "Cartesian skepticism". The works of Sextus Empiricus (c. 160-210 CE) were a source of inspiration for Descartes, but he did not use the Pyrrhonian skepticism. Descartes also wanted to provide the Roman Catholic Church with a new philosophical basis when it became clear that its Aristotelianism and its Scholastic methods had failed. In order to start from a new philosophical principle, he began with doubting everything as it was clear to him that the truth which was proclaimed by Scholasticism and its methods was a false one. In his Discours de la méthode pour bien conduire sa raison, et chercher la vérité dans les sciences (1637 CE) he rejected the Scholastic tradition of the Disputatio, which for Descartes lead to nothing but endless discussions on so-called problems and which did not lead to any significant result. From Descartes on (most) philosophers would create their world-views by themselves and no longer rely on the Scholastic Disputatio and its foundations
(see also The Structure of the Mind: Outlines of a Philosophical System, Francesco Belfiore, University Press of America, 2004, p. 6).

The basic approach of Descartes to the discovery of truth was to trust only those ideas which he felt could be demonstrated with the certainty of a mathematical proof. The way that he arrived at such a level of proof was to doubt and discard whatever was not clear and distinct in his own mind as determined by his reason, to a certainty at least that of his own self-consciousness of his own existence. Those ideas which could stand up to such a test he considered to be self-evident or axiomatic truths (which he called innate ideas); using these as a foundation, he then built the rest of his system upon them. Based on a skeptical approach René Descartes (1596-1650 CE) raised three epistemic doubts at the outset of his Meditationes de prima philosophia, in qua Dei existentia et animæ immortalitas demonstratur. Descartes first discards all belief in things which are not absolutely certain, and then tries to establish what can be known for sure. The first doubt regards knowledge that comes from the senses; the second invests the very existence of material objects; the third is the most powerful, encompassing the previous two ones. What if you were but the creation of an omnipotent evil deceiver, who 'engineered' you so to systematically get all of our opinions wrong? This is the famous evil deceiver hypothesis, also known as the hyperbolic doubt. Descartes came to the point where he doubted everything, except that he existed, which he put forward in his Meditationes de prima philosophia, in qua Dei existentia et animæ immortalitas demonstratur (Meditation II) as "Cogito Ergo Sum" (E: I think/know therefore I am, cogitare meaning 'to know'). His method of radical doubt lead to a single certainty and a theory of knowledge based on subjectivity linked to a theory of ultimate reality based on 'thinking substances' as one class of existence. Starting from the cogito, he moved in proving the existence of the external realm, God and the material world. Mind was being put forward as a self-contained sphere of enquiry besides matter. The idea of self-refutation leading to this axiom, "Cogito Ergo Sum", as such was not entirely new as both Plato (424/423-348/347 BCE) and Aristotle had mentioned it before, Plato spoke about the "knowledge of knowledge" and Aristotle explains the idea in his Nicomachean Ethics. Augustine of Hippo (354-430 CE) used the idea in his work De Civitate Dei contra Paganos (426 CE) (11.26): "Si enim fallor, sum" (E: If I am mistaken, I am). With René Descartes, Western philosophy took a new start and moved away from the rigid boundaries of Medieval scholasticism and Thomism or Neo-Aristotelianism. Descartes believed that he could then use his new method of reasoning to build on such a first principle, ultimately leading to the unification of all knowledge. Descartes would put forward his philosophy in Le traité du monde et de la lumière (Le Monde) which was only completely published in 1677. Descartes postponed its publication when he heard about the condemnation of Galileo Galilei (1564-1642 CE).

Descartes took the "cogito" as the first principle (principia neutra), from which he derived the other principles oh his philosophy. This reflects Avicenna's (ca. 980-1037 CE) "Suspended in Space" theory, in which man is a part of an intellectual circle larger than this life and only though his reasoning capabilities, does he envision himself, to be alive
(see also Kitab Al-Shifa, Avicenna and Avicenna's De Anima in the Latin West, Dag Nikolaus Hasse, 2000, Warburg Institute. p. 81 an 92). As such the proof of Descartes, which he derives from his "Cogito Ergo Sum", is a logical or conceptual proof of the existence of the concept that he thinks, but not a metaphysical proof of his existence or being as such. His proof remains at the level of a "second intention". Medieval philosophers used "intention" as synonymous with "concept", so that the answer that a philosopher gives to the question of an intention's ontological status follows from his resolution of the nature of a concept. According to medieval philosophy, there are two basic conceptual levels upon which we work. The first is the level of "first intentions" (Intentio prima = actus quo mens in ens reale tendit or the act by which the mind tends to a real being). Those are ideas that refer to things. But they also further abstracted from the first to the second intention (Intentio secunda = actus quo mens in ens rationis tendit or the act by which the mind tends to a being of reason) by taking a concept of another concept and referring to it, resulting in an idea about an idea about an object, which is called a "second intention"
(see also The Cambridge History of Later Medieval Philosophy: From the Rediscovery of Aristotle to the Disintegration of Scholasticism, 1100-1600, Norman Kretzmann (Editor), Anthony Kenny (Editor), Jan Pinborg (Editor), Eleonore Stump (Editor), Cambridge University Press, 1982, p. 492 and The Terms "Prima Intentio" and "Secunda Intentio" in Arabic Logic, Kwame Gyekye, Speculum Vol. 46, No. 1 (Jan., 1971), pp. 32-38). Man as a being (substance, essence) is a first intention, while the thinking (cogito) of man refers a second intention, because it represents only the concept of thinking, without actually referring to the physical man himself. The "Cogito Ergo Sum" proves the concept of a thinking man as a second intention, given the definition Descartes provides. A proof on the level of a second intention remains a conceptual or logical proof and does not prove it's being or essence. Absolute proofs are only possible at the level of "second intentions", but they cannot leap to the world of physical particulars. With his "Cogito Ergo Sum", Descartes provides an instrument to apply logic to the existence of himself thinking which necessarily approves his point. Presenting a definition which complies with the implicit premise which one wants to approve, makes sense logically, but not metaphysically. This approach leads to the separation of mind and matter or Cartesian Dualism and the necessity of God's existence
(see also Dualism, Edward N. Zalta (ed.), Robinson, Howard, The Stanford Encyclopedia of Philosophy ((Winter 2012 Edition)).

Descartes believed that the universe consists of two types of substance: mind and matter. These two substances are completely distinct and independent of each other, and both depend upon God for their existence. The main characteristic of mind is the activity of thinking; for matter it is the occupation of space. The substance of mind (also included in this category is the substance of the soul) can think due to the power of God who created and maintains it, and the validation of our certainty regarding the truth of the innate ideas depends upon the truthfulness of the Creator (which is infinite, according to Descartes). This lead to Cartesian Dualism, which was characterized by an absolute separation between an incorporeal mind and a mechanical material body
(see also What Am I?: Descartes and the Mind-Body Problem, Joseph Almog, Oxford University Press, 2005). In De homine (1662 CE), Traité de l'homme (1664 CE), La description du corps humain (1647 CE) and Les passions de l'âme (1649 CE) Descartes wrote about his view on the mind-body problem, putting forward the separation of body and soul and moving away from the medieval view (Aristotelian) on the mind-body problem and the medieval theories of conscience. Truth cannot come to us through the senses as was put forward by Aristotle. Descartes regarded the pineal gland as the principal seat of the soul and the place in which all our thoughts are formed and through which he tried to solve the 'problem of interaction'. A consequence of Descartes' separation of body and soul was a rigid dualism. This dualism of knowing (mental and material) lead to two chasms in modern thought: the ontological (between mind and body) and the epistemological (between subject and object). The body is part of the material world, while the soul is not and therefore is not subjected to the mechanical laws of nature (causality) and has no spatial extendedness. Causality acts in the material world and is based on matter in motion, 'extended substances', obeying separate material laws. Introspection for Descartes became the basis of certainty, while scientific knowledge of the external world depended on the laws of matter and motion. Philosophy finally produced a scheme of thought about the material world accessible for mathematics and safely separated from the mind. For René Descartes, once created by the hand of God, the machine of nature operates on its own. The world is governed by mechanical laws rather than by any teleological principle (Aristotle) or animate world-soul (Plato).

Science and medicine could intervene in the human body without touching the soul as opposed to the theory of Aristotle. In De Anima (350 BCE) (E: On the Soul) and the Parva Naturalia, Aristotle had postulated the union of body and soul by saying that the soul is the form of the body. For Aristotle the intellect was an aspect of the soul and the soul is the form of the body, not a separate substance. This controversy was part of the classical antagonism between dualism and monism. The dualists accept matter and mind as on equal basis. There are three varieties of monists, those who put mind inside matter, those who put matter inside mind, and those who identify matter with mind. Of the 17^th century rationalists, Descartes adhered to dualism, Spinoza to neutral monism, and Leibniz to monads.

Several reactions appeared to the mechanical philosophies of Descartes, Pierre Gassendi (1592-1655 CE), Thomas Hobbes (1588-1679 CE), and Robert Boyle (1627-1691 CE), which reasserted the fundamental organic unity of nature, such as Cambridge Platonism and vitalism.

Baruch Spinoza (1632-1677 CE) created a new philosophy as a reaction to René Descartes's (1596-1650 CE) dualism. Spinoza put forward a concept of causality that explains the infinite phenomenal universe in terms of a single substance (monism), God or Nature ("Deus sive natura"), without recourse to a transcendent being, origin, or goal required to render the order of things intelligible. For Spinoza God or Nature has no purpose or plan for the universe and the universe simply exists because it could not fail to exist. The universe was not created with any predetermined goal or plan in mind; instead the universe simply follows from God's essence in just the way that the properties of a circle follow from the essence of the circle. Spinoza rejected the transcendent 'Ideas' of Plato (424/423-348/347 BCE) and the immanent 'Forms' of Aristotle (384-322 BCE). For Spinoza, God is infinite, but immanent in the infinity of Nature (substance under the attribute of extension) and its eternal laws, outside or beyond which there can be nothing (no transcendent realm). Only the noetic (real) phase exists and there is no noematic (non-real) phase. Both Nature and God are infinite and therefore both necessarily need to be one. God or Nature is 'causa sui' or self-determined, Spinoza contends, but only in the sense of being subject to the immutable laws of its own essence as opposed to Theism. There is nothing arbitrary in Nature, no moment of creation and no external intervention, for there is nothing conceivable outside Nature. Nature, then, is nothing but its effects (the attributes and modes or states of substance) and therefore everything within Nature is subjected to the laws of causality. The finite mode of phenomenal elements and the infinite flux of their causal interaction are not reflections or expressions of Nature; rather, they are Nature, elements structured by the natural law of the whole but at the same time constituting the whole by their reciprocal activity. Nature actively creating itself in its attributes and their various modes (Natura Naturans) is only the obverse of Nature as the existing, established structure or system of the universe (Natura Naturata). Both the elements and the whole are necessary and complementary aspects of causality. Spinoza also defends a materialist position with regard to human nature, rejecting the Cartesian dualism of mind and body in favor of monism, a single substance with attributes of thought and extension. The human mind of Spinoza is inseparable from the human body; human intelligence is nothing more than the mental correlate of the physical complexity of the body. This means that human beings are to be understood as natural bodies and therefore by means of the same natural laws that apply to all other phenomena. This viewpoint of Spinoza on matter as a 'causa sui' or self-determined entity, also stands in the tradition of atomists such as Democritus (ca. 460-370 BCE), Epicurus (341-270 BCE), Titus Lucretius Carus (ca. 99-ca. 55 BCE), Pierre Gassendi (1592-1655 CE) and John Locke (1632-1704 CE)
(see also Cosmic Understanding: Philosophy and Science of the Universe, Milton K. Munitz, Princeton University Press, 1990, p. 192 and The Selected Works of Arne Naess: Volumes 1-10, Arne Naess, Springer Science & Business Media, 2007, p.383)

The Cartesian dualism was unified using Spinoza's God. Spinoza created a radical monism in which the single underlying substance of all reality was what he identified as "Deus sive natura" (God, or Nature). For him, God, an abstract and impersonal first principle, is an absolute and infinite substance. It is the one reality that can be in itself and conceived by itself. God is the necessary cause in the order of being. An important aspect of Spinoza's God, that would be the centre of his philosophy, was that his God is similar with Nature as both are infinite. The concept of an infinite universe was also present in the philosophy of Giordano Bruno (1548-1600 CE). God/Nature possessed two attributes knowable by man: mind (thought) and matter (extension), which duality we also find with Descartes but are united into one substance by Spinoza. Spinoza in his philosophy uses substance, attribute and modes to describe reality. Substance is the underlying reality beneath things, which contains both mind and matter as opposed to the dualism of René Descartes. A substance is a 'causa sui' as it it its own cause and it exists on its own (Ethica, I, definition 3). An attribute is that which the intellect perceives as constituting the essence of substance (Ethica, I, definition 4). Humans, are capable only of finite knowledge, and therefore we can know only two attributes: mind (thought) and matter (extension), that is, God's mind and God's body as the only parts of his infinite nature known to man. Modes represent everything which follows from the necessity of the nature of God. Modes are the infinite manifestations of the divine substance's attributes. A mode is any individual thing or event, any particular form or shape, which reality transiently assumes. The divine extension is thus manifested in an infinity of concrete bodies, while the divine thought is manifested in an infinity of ideas. Everything in the world is thus a mode of God's attributes. Spinoza makes the distinction between attributes and modes of substance, from which we can conceive within the oneness of reality a bipolar manifestation of the oneness, distinguishing and uniting the creating (attribute) and the created (modes). Spinoza calls the first pole 'natura naturans' (nature nurturing) and the second 'natura naturata' (nature nurtured). In his philosophy he dissolves the Cartesian dualism by making thought and extension attributes of the same substance. Spinoza holds that ideas and their objects correspond, meaning that valid knowledge is possible (Correspondence Theory of Truth). His most important works are the Tractatus Theologico-Politicus (1670) and the Ethica More Geometrico Demonstrata (1677). The application of geometric (Euclidic) or deductive reasoning to moral philosophy by Spinoza in his Ethica More Geometrico Demonstrata, in which he opposed the mind-body dualism of René Descartes, marked the dawn of Enlightenment
(see also Spinoza on Monism, Philip Goff, Palgrave Macmillan, 2011).

Spinoza rejects the dualism of (human) mind and body of Descartes. The unity of mind and body as one substance is in contrast to Descartes' belief that mind and body are separate substances. Mind and body for Spinoza are one and the same in substance, differing only from the point of view taken on its attributes. Substance which is one, can be perceived by it's different attributes, which are mind and body. Concerning the existence of individual beings, Spinoza postulated the concept of the conatus, which is an innate inclination of a thing to continue to exist and enhance itself (Ethica, III, proposition 6 and 7). mas as an intelligent being his essence strives towards understanding, which is the conatus intelligendi. With regard to knowledge Spinoza puts forward the concept of ideatum in a correspondence theory of knowledge. An ideatum corresponds to an idea and is what an idea is of, that is, the thing which is presented in an idea. Truth arises when an idea corresponds with its ideatum. Spinoza distinguishes three levels of knowledge, going form inadequate to adequate ideas which correspond with their ideatum. The first level is by means of perception by the senses and here he distinguishes knowledge from random experience of individual thing (experientia vaga) and knowledge from signs (ex signis). When man reaches the second kind of knowledge, reason (ratio), he ascends from an inadequate to an adequate perception of attributes of things. This is the level of scientific and mathematical knowledge. Finally man reaches intuitive knowledge (scientia intuitiva) where he "proceeds from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the essence of things". At this stage man perceives reality sub specie aeternitatis: "Est, uti diximus, haec idea, quae corporis essentiam sub specie aeternitatis exprimit, certus cogitandi modus, qui ad mentis essentiam pertinet, quique necessario aeternus est." (Ethica V, Prop. XXIII, Scholium)
(see also The Cambridge Companion to Spinoza's Ethics, Olli Koistinen, Cambridge University Press, 2009).

Spinoza developed a theory of human passions and human freedom in order to escape the rigid determinism arising from his non-dualism of mind and body. With regard to freedom he uses a similar concept as the Stoics, man is free when he acts in accordance to nature which he is capable of when he understands nature. Emotions are physical afflictions we conceive as ideas. Spinoza regards joy (laetitia) and sadness (tristitia) as the two basic emotions (cupiditas) and all other emotional states are variations of these two. Spinoza distinguishes passive and active emotions. Passive emotions are a reaction to external causes, while active emotions arise when man reaches towards understanding (conatus intelligendi). By capturing emotions in notiones communes man can understand them and act accordingly. True happiness for Spinoza exists in understanding emotions. The highest level of happiness (beatitudo) is the 'Amor intellectualis Dei'. This intellectual love towards God is part of the infinite love with which God loves himself. This intellectual love towards God is quite different from the primitive anthropomorphic concept of God of the common man. When understanding ethics and emotions 'sub specie aeternitatis' man no longer needs this primitive concept of an anthropomorphic God. For those who are not capable to reach this level of understanding a pious live is the best way to live. But one should always remind the last sentence of the Ethica: 'Sed omnia præclara tam difficilia quam rara sunt'
(see also The Cambridge Companion to Spinoza's Ethics, Olli Koistinen, Cambridge University Press, 2009).

Gottfried Wilhelm Leibniz (1646-1716 CE) was one of the most important philosophers of his century and stood in the Cartesian (rationalist) and Scholastic tradition. As a philosopher he stood in the rationalist tradition, in which conclusions are produced by applying reason to first principles (ultimate, irrefutable truths) or prior definitions rather than to empirical evidence. Leibniz rejected the dualism of Descartes and the monism of Spinoza. Leibniz contends that because the things we perceive using our senses are divisible into smaller parts, there's a possibility that all things are compounds or aggregates. In the Meditationes de Cognitione, Veritate et Ideis (1684) he dealth with the theory of truth and defined his theory of knowledge, which was critical for Descartes. In the Discours de métaphysique (1686) Leibniz develops his philosophy concerning physical substance, motion and resistance of bodies, and God's role within the universe. Leibniz put forward his animistic and monistic ideas in La Monadologie (1714 CE): there is a world of creatures, of living beings, of animals, of entelechies, of souls in the least part of matter. In La Monadologie he discusses the nature of monadic perception and consciousness, the principles which govern truth and reason, and the relation of the monadic universe to God. He defines a monad as a simple substance which cannot be divided into parts and describes three levels of monads. Monads are the point-like constituents of reality, and they possess a number of characteristics that are related to mental qualities. Leibniz's Neoplatonic panpsychism (animism, vitalism) was also based on La Monadologie, or science of monads. Vitalism presumes a monadological rather than atomistic ontology. In Leibniz's 'monadaology' all substances are different from one another. Vitalism affirmed the life of all things through a reduction of Cartesian dualism to the monistic unity of matter and spirit. Monads are similar with atoms in a number of ways, the difference being, atom is lifeless and material, whereas monads are dynamic and nonmaterial. Substance, according to Leibniz, must contain life or a dynamic force. Whereas the atom is lifeless and static by itself and needs to be acted upon (mechanical causality), the monads are capable of action on their own (non-causality). Like Spinoza, Leibniz created a deterministic view of reality. Because every monad is under a pre-established harmony, and each monad already has its own purpose, everything is already determined.

For Leibniz in La Monadologie, human reasoning was based on two great principles, that of contradiction and that of sufficient reason. To these two major principles Leibniz added four more: the principle of the best, the predicate-in-notion principle, the principle of the identity of indiscernibles, and the principle of continuity. In La Monadologie Leibniz also argued that God is supremely perfect, and that therefore God has chosen the best possible plan for the universe. God's plan for the universe necessarily produces the greatest amount of happiness and goodness, because it reflects God's absolute perfection. Voltaire (1694-1778 CE) would criticize Leibniz's optimism on "the best of all worlds" in his satire Candide, ou l'Optimisme (1759) after the 1755 Lisbon earthquake which devastated the city. Leibniz published the Theodicy (1710) on the problem of evil and the Nouveaux essais sur l'entendement humain (E: New Essays Concerning Human Understanding) (1765 CE) on the philosophy of mind against An Essay Concerning Human Understanding of the empiricist John Locke (1632-1704 CE).

Influential contributions to philosophy were also made by many other thinkers in this period and at the dawn of Enlightenment, such as Galileo Galilei (1564-1642 CE), Pierre Gassendi (1592-1655 CE), Nicolas Malebranche (1638-1715 CE), and Isaac Newton (1642-1727 CE).

The Cambridge Platonists of the 17^th century, such as Ralph Cudworth (1617-1688 CE), Henry More (1614-1687 CE), Bishop Richard Cumberland (1631-1718 CE), and Joseph Glanvill (1636-1680 CE), reacting against humanistic naturalism, "spiritualized Puritanism" by restoring the foundations of conduct to principles intuitionally known and independent of self-interest. The Cambridge Platonists, concerned that the immense movement towards a world-machine paradigm could only support the most radical Protestant and atheist factions in the ongoing religious and political conflicts attempted to refute its foundational premises and to reintroduce the world-soul or 'anima mundi' into the intellectual understanding of nature. The Cambridge Platonists retained the dualistic structure of mind and matter assumed by Descartes and attempted to bridge the gap by the reassertion of plastic natures and the 'anima mundi' as organic links.

The Roman Catholic Church did not accept the Cartesian skeptical and dualistic solution or other new solutions for the problems of Thomism (Neo-Aristotelianism) and would be left behind in the development of science, philosophy and theology. The Roman Catholic Church would not catch up until the Second Vatican Council or Vaticanum II (1962-1965 CE). Roman Catholic Thomistic dogmatism had put a deadlock on its philosophical and theological development, which would increasingly alienate it from reality and hinder Roman Catholic scientists and philosophers to participate in scientific and philosophical progres. Scholasticism would gradually move away from its Aristotelian physical basis, but no new connection with the physical world could be made, which would increasingly isolate it from scientific and cultural progress. Blaise Pascal (1623-1662 CE) would also criticise the rationalism of Descartes, and sympathized with the Jansenist movement of the Flemish bishop Cornelius Jansen (1585-1638 CE), which in France centered around Port-Royal-des-Champs, an abbey of Cistercian nuns. Jansenism arose out of the theological problem of reconciling divine grace and "liberum arbitrium" or human freedom. The resulting conflict between Jesuits and Jansenists became known as the formulary controversy.

Empiricists hold that most of our knowledge is empirical (or a posteriori). They "begin with" sensory ideas which form the source or basis for (or object of, or test for) a posteriori knowledge. Like rationalists they have a faith in human reason, but they have a different conception of the nature of "reason", one based upon sensory experience rather than upon a priori reasoning. The British Empiricists maintain that deductive reasoning can only reveal the logical connections between our ideas; it never increases our knowledge of what exists. British Empiricism would develop somewhat after Continental Rationalism and mostly during the Enlightenment. Peter Abelard (1079-1142 CE) had written his work Sic et Non (1122 CE) in which he demonstrated that the truths of revelation were not so clearcut. In the introduction of this work he put forward: "dubitando enim ad inquisitionem venimus; inquirendo veritatem percipimus" (E: through doubting we come to questioning and through questions we perceive the truth) as a dialectical method of intellectual reflection or Socratic method that lays the arguments of two opposing points of view side by side for comparison. This early form of Abelard's Sic et Non method relies on the "empiricist axiom" (Aristotelian) that knowledge has its origin in sensory experience. The British Empiricists would somehow follow in his footsteps.

Francis Bacon (1561-1626 CE) is described as an empiricist and after him Thomas Hobbes (1588-1679 CE). John Locke (1632-1704 CE), George Berkeley (1685-1753 CE), and David Hume (1711-1776 CE) were the pioneers of empiricism in the 18^th century Enlightenment.

In 1620 Francis Bacon (1561-1626 CE) published his Novum Organum Scientiarum (part of the Instauratio Magna) or The Novum Organum meaning to provide a new instrument, i.e. new instrument of natural philosophy, thereby referring to Aristotle's work Organon. In his Novum Organum, Bacon details a new system of logic he believes to be superior to the old ways of Arirstotelian syllogism. The culmination of Bacon's philosophical thought was the publication of Francisci de Verulamio, summi Angliae cancellarii, Instauratio magna (1620). This volume includes a six-part division of his whole philosophical programme (Instauratio Magna), the incomplete second part of this plan (Novum Organum), a sketch of the third part (the phenomena of the universe, or a natural and experimental history for the foundation of philosophy), and a catalogue of particular histories. His main criticism of Aristotle was that deduction from first principles was impossible in reality - the Greeks had a belief in the perfection of the cosmos, and so deduction could find answers to fit their view of the universe.

Ever since the great revolution which produced modern science, attempts have been made to create a science of society on par with the sciences of nature. Thomas Hobbes (1588-1679 CE) would develop the first political philosophy based on the new scientific developments. He lived during a major turning point of European scientific and intellectual history when Galilei and Kepler, Bacon and Descartes developed new scientific horizons. Hobbes stood clearly and completely on the side of the philosophy of the world-machine in his methodology and his explicit ideology. He also attempted to collapse the Aristotelian dualism between physics and mathematics as theoretical sciences and politics and ethics as practical sciences by insisting that society itself was subject to the laws of geometry.

Thomas Hobbes was the first modern philosopher to establish a relation between empiricism and nominalism. The central principles of his philosophical system derives from his work on the physiological origin of perception and rationalization. In his Elementorum philosophiae sectio prima De corpore (1655 CE) Hobbes put forward that the subject of philosophy is devoted to "bodies". And "body" was synonymous with substance, thereby breaking with the scholastic tradition. From his ideas on perception he developed a scientifically based epistemology and his nominalistic theory of universals would be at the heart of his epistemology. The ideas which he developed about perception would imply a changing view on the position of Aristotelian metaphysics. The advance in science was thought to necessitate a retreat by metaphysics as scientific progress contradicted the notion of static natures and ideas which had been at the heart of Scholasticism. Human understanding started from initial sense perceptions which serves as the foundation for all higher conceptualization and rationalization. This physical epistemology necessarily implied that only those things which confront the senses are capable of being conceptualized. The mechanical principles governing perception (optics) are also the same as those governing rationalization and there exists no rationalization without perception. The (mechanical) law of cause and effect only acts on a local scale, meaning that all activity is the direct result of an immediately prior (causal) motion. The law of cause and effect not only governs perception, but also the way the mind acts upon stimuli. As a consequence there do not exist static ideas or universals as all knowledge is derived from (subjective) perception. Hobbes still believed in a coherence of the natural principles governing physics and epistemology and he did not yet come to the skeptical conclusions of David Hume concerning human understanding of reality. Hobbes adhered to the nominalist maxim "there is nothing universal but names", so there are neither universal things nor universal ideas. Names do not exists as universals themselves, but only as universal and singular names: singular names name one thing, while universal names name more than one thing. It is this universality of certain names which, according to Hobbes, has lead some to think that there are also universal things. Although the name is universal, the thing signified is not universal, for there are no universal things to signify. From his mechanical world view he would limit philosophy to the attempt to ascertain future effects from known causes or prior causes from known effects
(see also Nominalism and Literary Discourse: New Perspectives, Hugo Keiper, Christoph Bode, Richard J. Utz, Rodopi, 1997, p. 288 and Thomas Hobbes, Otfried Höffe, SUNY Press, 2015, p. 97 and Thomas Hobbes' Physical Philosophy and its Implications toward the Religious Language of Scripture, Scott David Foutz, Quodlibet Journal: Volume 1 Number 4: July 1999)

Hobbes travelled to continental Europe on several occasions, meeting Galileo Galilei (1564-1642 CE), René Descartes (1596-1650 CE) and others. In 1636 Thomas Hobbes travelled to Italy where he met with Galileo Galilei. As a result Hobbes would develop the view that only material things exist as opposed to the dualism of Descartes. From this mechanistic view on According to Hobbes human beings are physical objects and sophisticated machines all of whose functions and activities can be described and explained in purely mechanistic terms. Even thought itself, therefore, must be understood as an instance of the physical operation of the human body. With the influence of Galileo, Hobbes would develop his social philosophy on principles of geometry and natural science and wanted to create a new science of political motion. The centerpiece of the new political mechanics would be the principle of endeavor: the conatus. Specific desires and appetites arise in the human body and are experienced as discomforts or pains which must be overcome. Thus, each of us is motivated to act in such ways as we believe likely to relieve our discomfort, to preserve and promote our own wellbeing. In The Elements of Law Natural and Politic (1640) with its two parts on human nature and on the body politic, Hobbes stated that conatus is the "internal beginning of animal motion". All motion of bodies consists of elementary motions he called 'endeavors'. They are motions 'made in less space and time than can be given', and they obey the (physical) law of persistence or inertia. A body strives to preserve its state and resist the causal power of other bodies. I call this the conatus-principle. Hobbes' argument for social contract and sovereign is based essentially on this model derived from the new physics of Galileo Galilei. He proves that the natural conatus makes people strive to preserve their lives and therefore to get out of the destructive state of nature; commit to mutual contracts; keep the contracts unless some external cause otherwise determines; and establish a permanent sovereign power that Hobbes calls 'an artificial eternity of life'. All this is determined by the fundamental laws of nature, essentially, by the conatus-principle
(see also Encyclopedia of Religion and Nature, Bron Taylor, A&C Black, 2008, p. 1278)

In his Leviathan or The Matter, Forme and Power of a Common Wealth Ecclesiasticall and Civil (1651) Hobbes was the first to apply this methodology from the natural sciences systematically to political philosophy and is the originator of modern political philosophy, including the modern theory of a "social contract" between individuals and society. Hobbes defended a range of materialist, nominalist, and empiricist views against Cartesian and Aristotelian alternatives
(see also States, Citizens and the Privatisation of Security, Elke Krahmann, Cambridge University Press, 2010, p. 22 and The Political Philosophy of Hobbes: Its Basis and Its Genesis, Leo Strauss, University of Chicago Press, 2014).

John Locke (1632-1704 CE) was the most influential English Enlightenment philosopher. He developed a theory of human knowledge which supported the emerging experimental science. Locke denied the existence of Cartesian innate ideas and considered our mind to be a 'tabula rasa' (blank slate). For the 'tabula rasa' concept, John Locke was inspired by Philosophus Autodidactus (The Self-Taught Philosopher) a translation by Edward Pococke (1604-1691 CE) of the novel Ḥayy ibn Yaqẓān (The Improvement of Human Reason: Exhibited in the Life of Hai Ebn Yokdhan) of Ibn Tufail (ca. 1105-1185 CE). The Ḥayy ibn Yaqẓān was an allegorical novel inspired by the philosophy of Ali al-Husayn ibn Sina (Avicenna) (ca. 980-1037 CE) and Sufism. Ibn Tufail in his novel demonstrated Avicenna's theories of empiricism and tabula rasa as a thought experiment. Locke was also influenced by Descartes and distinguished experience into sensation (external) and reflection (internal) whereby sensation precedes reflection but the latter does not only come from the former. In his Letters Concerning Toleration (1689-92) in the aftermath of the European wars of religion, Locke formulated a classic reasoning for religious tolerance. His most important philosophical work is An Essay Concerning Human Understanding, where Locke tries to determine the limits of human understanding. The original impetus for the writing of An Essay Concerning Human Understanding was a discussion about the principles of morality and revealed religion. In the four books of the Essay Locke considers the sources and nature of human knowledge. As an empiricist Locke argues that at birth, the human mind is a sort of blank slate on which experience writes. Locke opposes the Platonic notion of the Eternal Forms engrained in the human mind. For Locke ideas are the materials of knowledge and all ideas come from experience. The relative merits of the senses, reason and faith for attaining truth and the guidance of life were a significant issue for Locke. Locke also deals with the nature of reason, the relation of reason to faith and the nature of enthusiasm. Should one accept revelation without using reason to judge whether it is genuine revelation or not, one gets what Locke calls a third principle of assent besides reason and revelation, namely enthusiasm. Enthusiasm is a vain or unfounded confidence in divine favor or communication (Essay IV, Ch. XIX, 4-9). Locke restores in his philosophy the equality of reason and faith, which was lost during the Middle Ages. According to Locke propositions about which the certainty of demonstrative knowledge is unavailable, our assent may be grounded upon faith in revelation; but Locke argued that the degree of our confidence in the truth of such a proposition can never exceed our assurance that the revelation is of genuinely divine origin, and this itself is subject to careful rational evaluation (Essay IV, Ch. XVI, 14). Since God has provided both avenues of belief for the benefit of human achievement, Locke supposed, they can never conflict with each other if properly used. Faith is appropriate, but only with respect to vital issues that lie beyond the reach of reason; to allow any further extent to non-rational religious convictions would leave us at the mercy of foolish and harmful speculations. In any case where revelation (understood as an extraordinary communication from God) and ordinary human reason coincide in support of the same truth, Locke argued, it is reason that provides the superior ground, since our assurance of the reliability of the revelation itself can never exceed the perfection of demonstrative certainty (Essay IV, Ch. XVIII, 4-11)
(see also Second Treatise of Government and a Letter Concerning Toleration, John Locke, Oxford University Press, 2016 and The World of Ibn Ṭufayl: Interdisciplinary Perspectives on Ḥayy Ibn Yaqẓān, Lawrence I. Conrad, BRILL, 1996, p. 1 and Trailblazers in Philosophy, Jeremy Stangroom, The Rosen Publishing Group, 2015, p. 29).

Locke supported the corpuscular theory of classical atomism and therefore rejected the the traditional idea of essence, as used by either Plato or Aristotle. In his corpuscular theory of matter, Locke stood in the tradition of Democritus (ca. 460-370 BCE), Epicurus (341-270 BCE), Titus Lucretius Carus (ca. 99-ca. 55 BCE) and Baruch Spinoza (1632-1677 CE) who postulated that matter exists 'sui generis' and is self-caused. This differs from the postion taken by Aristotle (384-322 BCE) in his Categories (350 BCE), for whom the form is what makes matter what it is (as the soul defines a living body). Locke in his natural philosophy had to deal with the problem of cohesion which arises from atomism and while doing this provided an epistemological foundation for the arising experimental science. His support for the 'corpuscular hypothesis' lead to the acceptance of the void against plenism and the principle of (local) contact action. He tried to develop a model of human knowledge which was a compromise between the absolute claims of the Aristotelian concept of 'scientia', starting from self-evident premises, and the emerging experimental science where knowledge was experience-based. In An Essay Concerning Human Understanding Locke distinguished between real and nominal essences. A real essence is what makes something what it is, and in the case of physical substances, it is the underlying physical cause of the object's observable qualities. A nominal essence however is an abstract idea that we make when we identify similar qualities shared by objects; the nominal essence is only the idea of those shared similarities. The episteme of a real essence for Locke was beyond the human powers of perception, while nominal essences consisted of observable surface properties. Locke also distinguished between primary and secondary qualities, where primary qualities are those properties of an object that are not related by definition to perceivers. The primary qualities are size, shape, motion, number, and solidity. On the other hand secondary qualities are related to perceivers by definition and so they are properties that an object can have only in relation to its being seen by someone
(see also Locke on Real Essence, David Owen, History of Philosophy Quarterly, Vol. 8, No. 2 (Apr., 1991), pp. 105-118 and The Oxford Handbook of Philosophy in Early Modern Europe, Desmond M. Clarke, Catherine Wilson, OUP Oxford, 2011, p. 26 and The SAGE Encyclopedia of Qualitative Research Methods, Lisa M. Given, SAGE Publications, 2008, p. 270 and John Locke and Natural Philosophy, Peter R. Anstey, OUP Oxford, 2011, p. 14 and British Philosophy and the Age of Enlightenment, Stuart Brown, Psychology Press, 2003, p. 44

Locke was the first to develop a modern theory of identity. He defines personal identity in terms of memory as he states that our conscious memories constitute our identities. His concept of personal identity was related to his atomism, because og which he could not use the Aristotelian concept of identit based on substance. Locke was influenced by Epicurean atomism and materialism, but in addition considered the human mind as a separate entity which was more than just the corpuscular parts which constituted the mind. Locke opposed the Augustinian view of man as originally sinful and the Cartesian position, which holds that man innately knows basic logical propositions. Instead Locke puts forward an empty mind, a blank slate or tabula rasa, which is shaped by experience, and sensations and reflections being the two sources of all our ideas. In Book II, Chapter XXVII, Of Identity and Diversity, of An Essay Concerning Human Understanding Locke puts forward his account of identity and personal identity. In this Chapter Locke explains the identity of the world's substances and entities, including his theory of personal identity for human beings. He defines the concepts of man, soul, and person, and determines what makes a person the same over time, despite changes both physical and mental while being based on a collection of atoms. Although man consists of atoms, he builds an identity through his life which is more than just the collection of atomic instances. Locke begins by stating that there are three substances that exist: God, material substance, and finite intelligences, or consciousnesses. Locke claims that the way in which an object is defined depends on its substance. God is an infinite, unchanging, immaterial substance. Material substances are also said to be unchanging at their most basic element, the atom. Material substances are formed into configurations and shapes that give rise to objects within the real world. Locke sees man as nothing more than the living animal which is in the shape of a man. Locke does not see the physical form to the human being as the seat of identity, and thus introduces the concept of the person. He defines the person as an intelligent being capable of rational thought, reason, and reflection. He says that the person is able to consider itself in different times and places, and be aware that it is the same self in these other situations. This person is the only basis, Locke argues, for the identity of a conscious entity, regardless of physical attributes. The continuation of the same functional organization and thus the same life for Locke is the criterion of identity for sameness of living things
(see also Personal Identity, John Perry, University of California Press, 2008, p. 33 and Locke, Hume, and the Treacherous Logos of Atomism, Robert J. Roecklein, Lexington Books, 2015, p. 96 and The Columbia History of Western Philosophy, Richard Henry Popkin, Columbia University Press, 2013, p. 385).

Locke defines one final substance that is part of each human in An Essay Concerning Human Understanding: the soul. He describes the soul only as immaterial and eternal, and asserts that each man has one. By postulating this immortal soul, morality can be enforced upon man through the principle of eternal reward or punishment by the final moral judge which is the for Locke the God of Nature. Locke puts forward Aristotelian/Thomistic arguments for the existence of God and attributes unity, infinity and eternity to God. According to Locke, the existence of God is an instance of demonstrable knowledge in any reasoning being. "Since I know intuitively that I exist as a thinking thing, and since nothing can be made to exist except by something else which both exists and has powers at least equal to those of each of its creations, it follows that from all eternity there must have existed an all-powerful cogitative being" (Essay IV, Ch. X 3-6). The Lockian theory of mind and consciousness also forms the basis of the insanity defence: one cannot be held accountable for acts of which one was unconscious
(see also John Locke: Resistance, Religion and Responsibility, John Marshall, Cambridge University Press, 1994, p. 151).

The main philosophical project of the Irish Anglican bishopGeorge Berkeley (1685-1753 CE) was to criticize the prevailing material philosophy of his time. George Berkeley criticized the materialism of René Descartes (1596-1650 CE), Nicolas Malebranche (1638-1715 CE), and John Locke (1632-1704 CE). His most important works are the Treatise Concerning the Principles of Human Knowledge (1710) and and Three Dialogues between Hylas and Philonous (1713). He is most well known for his maxim 'esse est percipi' or 'esse is percipi' (to be is to be perceived) on the principle of subjective idealism which he wrote about in his Treatise Concerning the Principles of Human Knowledge. The full version of the maxim is 'esse est percipi vel percipere' (to exist is either to be perceived or to perceive). Berkeley in his works develops a philosophy based on idealism and common sense. For him there is no material world, but there is a physical world, a world of ordinary objects. This world is mind-dependent, for it is composed of ideas, whose existence consists in being perceived. For Berkeley The wold is mind dependent, but not the mind of man, but the mind of God. For ideas, and so for the physical world, 'esse est percipi' (E: to be is to be perceived). Things only exist either as a result of their being perceived, or by virtue of the fact that they are an entity doing the perceiving. In these works Berkeley also defends idealism by attacking the materialist alternative of Descartes. Berkeley contends that no material things exist, not just that some immaterial things exist. Berkeley attacks materialism because it promotes skepticism and atheism. Skepticism is a result of the dualism of Descartes, because his materialism implies that our senses mislead us as to the natures of these material things, which moreover need not exist at all. According to Berkeley, Atheism is promoted because a material world could be expected to run without the assistance of God. However with his subjective idealism Berkeley moved Locke's empiricism in the direction of Hume's scepticism
(see also The Big Questions: A Short Introduction to Philosophy, Robert C. Solomon, Kathleen M. Higgins, Cengage Learning, 2013 and George Berkeley: A Reappraisal, Arthur David Ritchie, Manchester University Press, 1967, p. 58 and First Philosophy: Fundamental Problems and Readings in Philosophy, Andrew Bailey, Broadview Press, 2002, p. 196). and

David Hume (1711-1776 CE) developed a radical philosophical empiricism, skepticism, and naturalism. He lead empiricism to its extreme skeptical consequence of the inability of absolute knowledge. Hume applied the scientific methods of observation to a study of human nature itself to develop a naturalistic philosophy of man. He wrote A Treatise of Human Nature (1739-1740 CE), the Enquiries concerning Human Understanding (1748) and Concerning the Principles of Morals (1751), as well as the posthumously published Dialogues concerning Natural Religion (1779)
(see also The High Road to Pyrrhonism, Richard H. Popkin, Richard Henry Popkin, James E. Force, Hackett Publishing, 1993, p. 36 and David Hume: His Pyrrhonism and His Critique of Pyrrhonism, Richard H. Popkin, The Philosophical Quarterly (1950-), Vol. 1, No. 5 (Oct., 1951), pp. 385-407).

In A Treatise of Human Nature (1739) Hume set out to create a total naturalistic "science of man" that examined the psychological basis of human nature. For David Hume all sciences ultimately depend on "the science of man" and he founded all science and philosophy on an empirical investigation into human psychology. Hume stated that desire rather than reason governed human behavior. Custom and natural instincts are the basis of the common life. Custom, not reason, is the great guide of human life. Hume is considered to be a precursor of contemporary cognitive science, as well as one of the most thoroughgoing exponents of philosophical naturalism. Hume carried the empiricism of John Locke and George Berkeley (1685-1753 CE) to the logical extreme of radical skepticism. Hume's goal was to refute René Descartes (1596-1650 CE), and defend Berkeley. Hume argues that man gains knowledge from experience and that we should be skeptical of all other knowledge. According to Hume, little human knowledge can be derived from the deductively certain relations of ideas. He denied the possible existence of causal powers which underlie the regularities that we observe in nature. Since the causal interactions of physical objects are known to us only as inherently uncertain matters of fact, Hume argued, our belief that they exhibit any necessary connection (however explicable) can never be rationally justified, but must be acknowledged to rest only upon our acquired habits. In similar fashion, Hume argued that we cannot justify our natural beliefs in the reality of the self or the existence of an external world. From all of this, Hume concluded that a severe (if mitigated) skepticism is the only defensible view of the world
(see also Hume's Epistemology and Metaphysics: An Introduction, Georges Dicker, Routledge, 2002 and Ancient Epistemology, Lloyd P. Gerson, Cambridge University Press, 2009, p. 3).

The concept of our view on reality and on epistemology which Hume develops is related to the phenomenalism of George Berkeley as it has its roots in the senses. All our ideas about reality start from perception according to the classical axiom "Nihil est in intellectu quod non sit prius in sensu". Our belief in the reality of an external world is entirely non-rational but only rooted in belief. On the development of our ideas of the world around us, Hume stated there is a distinction between two different perceptions. The first is the root of all ideas which he called an impression and the second are the ideas themselves. While impressions are the direct, vivid, and forceful products of immediate experience our ideas are merely feeble copies of these original impressions ('vivacity' related to validity). By means of experience we create relations between our ideas by means of resemblance, contiguity of ideas and cause and effect, all of which only exist in the human mind but not in reality. Hume distinguishes between simple ideas and those which aggregate into complex ideas. Because all ideas come from impression, he concludes that all simple ideas come from simple impressions. To get the simple idea you abstract from a complex idea many impressions. In order to get to the core of all ideas, we have to trace our ideas back to the impressions from which they come. All human beliefs are the result from repeated applications of these simple associations and all of them are contingent and never give us absolute certainty. As for our believes there are, according to Hume, two sorts of belief. First of all there are relations of ideas which are beliefs grounded wholly on associations formed within the mind which have no external referent and which are therefore capable of demonstration. On the other hand there are matters of fact which are beliefs that claim to report the nature of existing things. These matters of fact are always contingent although we may have the illusion of certainty. For Hume causal reasoning can never be justified rationally as we can only assume the principle of uniformity of nature based on our experience or instinct, which leads us to the fundamental problem of induction. Our belief that events are causally related is only based on custom or habit acquired by experience but is not rooted in reality itself: "A cause is an object precedent and contiguous to another, and so united with it, that the idea of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other." Induction, like causation, can be used in daily life as long as we recognize the limitations of the knowledge we derive from induction and perceived causation. Hume's concept of empiricism ultimately lead to skepticism. In his Dialogues concerning natural Religion, Hume put forward the doctrine of natural belief which allows that certain beliefs are justifiably held by all, but he stated that belief in God is not a natural belief. Our belief in causality is (only a) a 'natural belief'
(see also David Hume: Reason in History, Claudia M. Schmidt, Penn State Press, 2010, p. 14 and The Mind of David Hume: A Companion to Book I of A Treatise of Human Nature, Oliver A. Johnson, University of Illinois Press, 1995, p. 46).

Hume in his Dialogues concerning Natural Religion discussed Natural Theology, which is an inquiry into the existence and attributes of God without referring or appealing to any divine revelation. The Dialogues follow the discussion of three thinkers debating the nature of God: Philo, Demea and Cleanthes and they are modeled after the De Natura Deorum of Marcus Tullius Cicero (106 BCE-43 BCE). The character Philo may refer to Philo of Alexandria (ca. 20 BCE-40 CE) and it is widely believed that this character presents views most similar to those of Hume. In the Dialogues Hume discussed the nature of True Religion and the nature of God's existence. Hume stated that man has a natural propensity to believe in a Supreme Architect, but this is an act of faith independent of reason (fideism). This refers to "Quid ergo Athenis et Hierosolymis?" (Tertullian (ca. 155-ca. 240 CE) in De praescriptione hereticorum 1.9). Hume's view on traditional religions was 'comptio optimi pessirna' (the corruption of the best things gives rise to the worst). On God's existence Hume argued that an orderly universe does not necessarily prove the existence of God as order and purpose not only appear as a direct result of design (argument from design, teleological argument), neither does the cosmological argument. The design argument does not prove the existence of God in the way man conceives him: all-knowing, all-powerful, and entirely beneficent (problem of evil). Hume rejected miracles in his Enquiry concerning Human Understanding as "a miracle is a violation of a law of nature" (Enquiry, 11.12/114): "A miracle is a violation of the laws of nature; and as a firm and unalterable experience has established these laws, the proof against a miracle, from the very nature of the fact, is as entire as any argument from experience can possibly be imagined." A perceived violation of a law of nature has no meaning and so we never have reason to believe miracle reports we are being told or read: " no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavors to establish" (Enquiry,On Miracles). Hume prefers a naturalistic interpretation of events when dealing with the testimony of a miracle. The mutual intolerance of traditional (monotheistic) religions did not exist in 'true religion' according to Philo: "True religion, I allow, has no such pernicious consequences: but we must treat of religion, as it has commonly been found in the world;... ". True religion was turned inward and away form the idolatry of traditional religions and supported the principles of genuine theism, and consisted mainly in assigning a deity as the source of nature's regularity. True religion as described by both Hume and Philo was also independent of morality and did not lead to pernicious consequences. It cannot guide our actions and therefore the dispute between theists and atheists was "merely verbal" according to Philo
(see also God, Hume and Natural Belief, J. C. A. Gaskin, Philosophy, Vol. 49, No. 189 (Jul., 1974), pp. 281-294 and Scepticism and Belief in Hume’s Dialogues Concerning Natural Religion, S. Tweyman, Springer Science & Business Media, 6 dec. 2012 and Hume's Aesthetic Theism, John Immerwahr, Hume Studies, Volume XXII, Number 2, November 1996, pp. 325-337 and Modern Philosophy (Second Edition): An Anthology of Primary Sources, Roger Ariew, Eric Watkins, Hackett Publishing, 2009, p. 638 and David Hume: Religion, IEP and Philo in Early Christian Literature: A Survey, David T. Runia, Uitgeverij Van Gorcum, 1993, p. 67).

David Hume developed a theory of the Self or better said the absence thereof. He rejects the notion of an immaterial substance, a mind or soul that persists through time on its own as an illusion. According to Hume we do not have an impression of the self, but the self is just a bundle of perception (bundle theory). We are never directly aware of ourselves, only of what we are experiencing at any given moment. Therefore the self is just a bundle of perceptions, like links in a chain. With regard to morality he discussed the is-ought problem in A Treatise of Human Nature (Treatise 3.1.1). We wrongfully derive what "ought" to be from what "is" and Hume completely severed "is" from "ought", which became known as Hume's Guillotine. On morality Hume developed his own moral sense theory. According to Hume's Enquiry concerning the Principles of Morals on moral philosophy our moral principles are (only) rooted in their utility, or usefulness and not in God or reason. Hume opposes the concept of 'practical reason' that to act morally is to have a rational grasp of moral truths. He defends an instrumental conception of practical reason, according to which the role of reason is only to find out which means helps achieve a given goal. Reason, for Hume, has no fundamental role in morality and so he denies that reason plays a determining role in motivating or discouraging behavior. For him the determining factor in human behavior is passion. Reason in these matters only helps us arrive at judgments, but our own desires motivate us to act on or ignore those judgments: "Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them" (Treatise 2.3.3). Therefore, reason does not form the basis of morality, it only plays the role of an advisor rather than that of a decision-maker. On free will Hume was a compatibilist which states that freedom and moral responsibility can be reconciled with (causal) determinism. Compatibilism states that one has the freedom to act according to his own motivation, without arbitrary hindrance from other individuals or institutions. It lead Hume to assume having the power to make moral choices by following your own desires: "By liberty, then, we can only mean a power of acting or not acting, according to the determinations of the will; this is, if we choose to remain at rest, we may; if we choose to move, we also may. Now this hypothetical liberty is universally allowed to belong to every one who is not a prisoner and in chains. Here, then, is no subject of dispute." in An Enquiry Concerning Human Understanding in 'Of Liberty and Necessity'
(see also Consciousness: An Introduction, Susan Blackmore, Routledge, 2013, p. 107 and David Hume: Reason in History, Claudia M. Schmidt, Penn State Press, 2010, p. 183-184 and David Hume’s Humanity: The Philosophy of Common Life and Its Limits, S. Yenor, Springer, 2016, p. 36 and Nature's Challenge to Free Will, Bernard Berofsky, OUP Oxford, 2012, p. 92).

The Age of Enlightenment was a philosophical movement in 18^th century Europe that sought to mobilize the power of reason (Greek: logos) in order to reform society and advance (scientific) knowledge. Attempts to reconcile science and religion resulted in a rejection of prophecy, miracle and revealed religion, often in preference for Deism. Originating at about 1650-1700, it was sparked by philosophers Baruch Spinoza (1632-1677 CE), John Locke (1632-1704 CE), Pierre Bayle (1647-1706 CE), Isaac Newton (1643-1727 CE) and Voltaire (1694-1778 CE). John Locke (1632-1704 CE) is generally considered as the founder of the Enlightenment movement in philosophy, while Immanuel Kant (1724-1804 CE) is considered to be the most important continental philosopher of the Enlightenment. The philosophers of the Enlightenment believed in the almightiness of human knowledge and defied the Scholastic tradition and the pre-established thoughts of the past ('Auctoritas aprobata'). Philosophers and scientists previously had committed the fallacy of argumentum ad ignorantiam. The argumentum ad ignorantiam is a logical fallacy which asserts that a proposition is true because it has not yet been proven false, it is "generally accepted" (or vice versa). Anything which cannot be understood by rational knowledge and the current status of sciences was defied as meaningless or superstitious. Philosophy became very popular among the intellectuals and people read philosophical works. However, the general concerns were about the practical use of our knowledge.
The Two Fundamental Characteristics of the Philosophy of Enlightenment are:

1. Faith in the European Reason and human rationality to reject the tradition and the pre-established institutions and thoughts
2. Search for the practical, useful knowledge as the power to control nature

Enlightenment was considered man's emergence from his self-incurred immaturity. Immaturity is the inability to use one's own understanding without the guidance of another. This immaturity is self-incurred if its cause is not lack of understanding, but lack of resolution and courage to use it without the guidance of another. The motto of enlightenment is therefore: Sapere aude! Have courage to use your own understanding! Immanuel Kant defined Enlightenment as der Ausgang des Menschen aus seiner selbstverschuldeten Unmündigkeit in Beantwortung der Frage: was ist Aufklärung ?, Königsberg, Berlinische Monatsschrift, 30^th September, 1784.

Thomas Hobbes (1588-1679 CE). John Locke (1632-1704 CE), and George Berkeley (1685-1753 CE) were the pioneers of empiricism in the 18^th century Enlightenment in England and Ireland.

People like Robert Boyle (1627-1691 CE), William Molyneux (1656-1698 CE), Archbishop Narcissus Marsh (1638-1713 CE), John Toland (1670-1722 CE), Jonathan Swift (1667-1745), Francis Hutcheson (1694-1746 CE) and Bishop George Berkeley (1685-1753 CE) were born or lived in Ireland an played a role in the Irish, English and Scottish Enlightenment.

The French Enlightenment or 'Siècle des Lumières' is associated with the French thinkers of the mid-decades of the 18^th century, the so-called "philosophes". In France the editing and publication of the Encyclopédie ou dictionnaire raisonné des sciences, des arts et des métiers, (published between 1751 and 1772) a comprehensive book of all the books about wisdom of all humanity, was attempted for the first time in the West. The Encyclopédie was edited by Denis Diderot (1713-1784 CE) and Jean-Baptiste le Rond d'Alembert (1717-1783 CE) Many of the contemporary French philosophers contributed to drafting the manuscripts and were called the Encyclopedists. Denis Diderot published his Pensées philosophiques (1746-1762) on Deism anonymously in the Netherlands. François-Marie Arouet or Voltaire (1694-1778 CE), Jean-Jacques Rousseau (1712-1778 CE) and Claude Adrien Helvétius (1715-1771) contributed to the Encyclopédie. The basic motive of this edition was the denial of the past and the resistance against Church authority. Encyclopédistes such as Voltaire were secularists or promoted a deist view. They proclaimed that nature was the only revelation God has ever made and thus the preoccupation with any other alleged revelation was superfluous. Additionally the Bible (and the Old Testament in particular) was considered contradictory in itself to pure reason and to the perfection of God. The Book of Nature was considered to be more trustworthy than the Book of Revelation as opposed to the Aristotelian (Thomistic) synthesis between science and faith of the Middle Ages.

Julien Offray de La Mettrie (1709-1751 CE), Paul-Henri Thiry d'Holbach (1723-1789), Georges-Louis Leclerc de Buffon (1707-1788 CE) were materialists and rejected supernaturalism. Julien Offray de La Mettrie wrote L'homme machine (1747, E: Machine man), wherein he rejected the Cartesian dualism of mind and body, and proposed the metaphor of the human being as machine. In this view the mind is also subjected to the mechanical laws of causation which Descartes had tried to avoid. Consciousness in this view is only an epiphenomenon of the material body. Baron d'Holbach's most important work is the Système de la Nature ou Des Loix du Monde Physique et du Monde Moral (1770 CE) in which he described the universe in terms of the principles of philosophical materialism. D'Holbach derived his mechanical determinism on Newtonian physics and Lockeian psychology, arguing that every event in nature, including all human thought and moral action, is the result of an inexorable chain of causation rooted in the flux of atomic motion. he also attributes all thought to images impressed on the mind's tabula rasa, or blank slate, in wholly mechanical fashion according to these same laws of motion, as John Locke (1632-1704 CE) had argued
(see also LaMettrie's L'Homme Machine, Aram Vartanian, Princeton University Press, 2015 and Système de la nature ou des loix du monde physique et du monde moral, Volume 1 and 2, Paul Henri Dietrich d'Holbach, 1770).

Key figures in the Scottish Enlightenment were Francis Hutcheson (1694-1745 CE), David Hume (1711-1776 CE) , Adam Smith (1723-1790 CE), and Thomas Reid (1710-1796 CE). Francis Hutcheson (1694-1746 CE), is considered to be the father of the Scottish Enlightenment, and championed political liberty and the right of popular rebellion against tyranny. Adam Smith (1723-1790 CE), in his monumental An Inquiry into the Nature and Causes of the Wealth of Nations (1776), advocated liberty in the sphere of commerce and the global economy. Adam Smith was the founder of classical liberalism and thereby opposed mercantilism. In The Theory of Moral Sentiments (1759) Adam Smith proposed a theory of sympathy, in which the act of observing others makes people aware of themselves and the morality of their own behavior. David Hume (1711-1776 CE) developed philosophical concepts that directly influenced James Madison (1751-1836 CE) and thus the Constitution of the United States.

The most important leaders of the American Enlightenment include Benjamin Franklin (1706-1790 CE) and Thomas Jefferson (1743-1826 CE). Jefferson was the principal author of the United States Declaration of Independence (1776). People such as Thomas Paine (1737-1809 CE), James Madison (1751-1836 CE), Thomas Jefferson, John Adams (1735-1826 CE), and Benjamin Franklin invented and adopted revolutionary ideas about scientific rationality, religious toleration and experimental political organization. The American Enlightenment developed along ideas such as Deism, liberalism, republicanism, conservatism, toleration and scientific progress.

Key figures of the German Enlightenment or 'Aufklärung' include Christian Wolff or Christian von Wolfius (1679-1754 CE), Moses Mendelssohn (1729-1786 CE), Gotthold Ephraim Lessing (1729-1781 CE), and Immanuel Kant (1724-1804 CE).

Immanuel Kant (1724-1804 CE) would cause a Copernican Revolution in philosophy by putting forward the principle of 'Mind Making Nature'. He developed transcendental idealism to prove synthetic a priori claims and that the mind provides a systematic structuring of its representations of nature. The human mind creates the 'Ding für mich' (phenomenon) as a representation of the 'Ding an sich' (unknowable thing in itself). Kant attempted to synthesize the Continental_rationalism of René Descartes- Baruch Spinoza- Gottfried Wilhelm Leibniz and the British Empiricism of John Locke- George Berkeley- David Hume into one so called Critical Philosophy of his own by being inspired by both, eliminating the faults of both thoughts and critically unifying the strengths of these opposing philosophical thoughts. Kant responded to his predecessors by arguing against the Empiricists ("Skeptizismus") that the mind is not a blank slate that is written upon by the empirical world a posteriori, and by rejecting the Rationalists' notion ("Dogmatismus") that pure, 'a priori' knowledge of a mind-independent world was possible. Immanuel Kant wanted to unite reason (rationalism, deduction) with experience (empiricism, induction) and to move beyond what he took to be failures of traditional philosophy and metaphysics. For Kant, reason itself is structured with forms of experience and categories that give a phenomenal and logical structure to any possible object of empirical experience. These categories cannot be circumvented to get at a mind-independent world, but they are necessary for experience of spatio-temporal objects with their causal behaviour and logical properties. These two theses constitute Kant's transcendental idealism and empirical realism. His most famous work is the Kritik der reinen Vernunft (1781), which was followed by the Kritik der praktischen Vernunft (1788) and the Kritik der Urteilskraft (1790).

Kritik der reinen Vernunft of Immanuel Kant.

In the Kritik der reinen Vernunft (1781) Kant deals with theoretical philosophy. Here he tries to solve the problem that man is not able to understand the divine order of the world. He moves the ordening principle within man, where man through his perceptive apparatus creates an internal order. Ordening takes place in time (number) and space (geometry) and applying (universal) categories (physics), experience and reason ('Vernunft'). Man perceives the 'Ding an sich', but only filtered through his perceptive apparatus, which generates the 'Ding für mich'. By putting the ordening principle or apparatus within man as a filter for perception, Kant tried to reconcile empiricism and rationalism, hereby solving the problem of the unknowability of the divine order by man, which had haunted philosophy since the demise of the mediaeval world-view. Man has an active internal ordening 'apparatus' and creates an internal model of reality ('ordo ab chao'), which is his (only) access to reality, which as such remains unknown (chaos). Man himself becomes a 'Ding an sich', thereby avoiding the problems of determinism with the concept of free will. Kant's philosophy lead to the autonomy of man (subject) in dealing with the world (object) and morality. He puts forward his Transcendental Doctrine of Elements and Transcendental Doctrine of Method. The Transcendental Doctrine of Elements cosists of the Transcendental Aesthetic and the Transcendental Logic, which in itself consists of the Transcendental Analytic and the Transcendental Dialectic. In the Transcendental Aesthetic he deals with sensibility and with objects as far as they can be perceived. Sense perception deals with what our sense can provide of the (external) world outside the human mind. Knowledge which is derived from sense perception is called 'a posterori' empricial knowledge. Knowledge which is present before or independent of sense perception is called 'a priori' concepts. 'A priori' concepts cannot be captured by sense perception and therefore they are considered as the subject of pure reason. 'A priori' concepts are characterized by necessity ("Notwendgikeit") and their general character ("Allgemeingültigkeit"). The 'a priori' concepts which are prerequisites for perceiving and ordning reality are the "reine Anschauungsformen" (Space and Time), the "reinen Verstandsbegriffe" (Categories) and the "reine Vernunftbegriffe" (Ideas). Kant gives two expositions of space and time: metaphysical and transcendental. The metaphysical expositions of space and time are concerned with clarifying how those intuitions are known independently of experience 'a priori'. The transcendental expositions attempt to show how the metaphysical conclusions might be applied to enrich our understanding. The concepts of time and space classify the sense perceptions. Kant's view of space and time rejects both the space and time of Aristotelian and Leibnizian physics and the space and time of Newtonian physics. Aristotle (384-322 BCE), in Book IV of his Physics, defined time as the number of change with respect to before and after, and the place of an object as the innermost motionless boundary of that which surrounds it. Gottfried Wilhelm Leibniz (1646-1716 CE) put forward that space and time are merely relations or determinations of things even when they are not being sensed. Isaac Newton (1642-1727 CE) put forward that space and time are real existences. For Kant space cannot be empirical and we can speak of space "only from the human standpoint" and space is a "transcendental ideality". The Categories classify sense perception and make it accessible or consitute it for the human mind. Man is capable to creat a unity of perception from the manifolds of sense data by means of "Transzendentale Deduktion". By applying Transcendental Deduction upon mental concepts they become objective. For Kant pure reason and sense perception must work together. Kant argued that sense experience is purely subjective without first being processed by pure reason (e.g. categorized). He also put forward that using reason without applying it to experience will only lead to theoretical illusions: "Begriffe ohne Anschauung sind leer, Anschauung ohne Begriffe ist blind". Kant proposed that objective reality is known only insofar as it conforms to the essential structure of the knowing mind. He distinguises between 'das Ding an sich' as it exists in the noumenal world without being perceived (unknowable to man) and 'das ding für mich' ("Erscheinung") how it presents itself to us through our senses and perception and becomes an object for the observer ("erkennenden Subjekt"). Only objects of experience, phenomena, may be known, whereas things lying beyond experience, noumena, are unknowable, even though in some cases we assume a priori knowledge of them. The "Ding an sich" exists beyond the ability of our sense-perception, it is only "intelligibel" and accessible for the "intellektuelle Anschauung". The "Ding an sich" is not accessible for theoretical philosophy. The existence of such unknowable 'das Ding an sich' can be neither confirmed nor denied, nor can they be scientifically demonstrated. Therefore, as Kant showed in the Kritik der reinen Vernunft, the great problems of metaphysics-the existence of God, freedom, and immortality-are insoluble by scientific thought. In his Kritik der reinen Vernunft Immanuel Kant opposes the old Aristotelian view that all synthetic judgment are a posteriori, while only analytic judgments are a priori. Kant argued that there are synthetic judgments which can be a priori (e.g. mathematics)
(see also Kant's Critiques, Immanuel Kant, Start Publishing LLC, 2013).

Immanuel Kant - Theory of perception.

In the Kritik der praktischen Vernunft (1788) (Critique of Practical Reason) Kant examines the basis concepts and laws of the intelligible ("intelligiblen") which lies beyond the appearances ("Erscheinungen"). In the Kritik der praktischen Vernunft Kant stated that morality requires belief in the existence of methaphysical concepts or "regulative Ideen". What cannot be known in theoretical philosophy can be though of practically. Only the "praktischen Vernunft" can make an intelligible and moral world beyond the phenomena accessible. The world of the "praktischen Vernunft" is being considered as the "Willensgrund" for moral behavior. Kan distinguishes between the "empirische" and "intelligiblen Charakter" of man. The empirical character of man is, like other empirical "objects" subjected to the cause-effect principles (causality) of the world of phenomena and sense-perception. All empirical actions are determined by external influences and are therefore not "free and determined. The intelligible character of man is not subjected to the law of causality as man is himself a 'das Ding an sich'. As a moral being, man has to its disposal a 'free will' ("freien Willen") which leads to spontaneous and undetermined causality. Actions derived from the intelligible character of man are therefore free. Freedom is the prerequisite for the human will to provide and develop its own laws. For Kant free will means the autonomy of the "praktischen Vernunft" (practical reason) of man. Within its practical reason man can put forward the goals and principles of his behaviour. The highest moral law of the free will is the so-called "Sittengestz" (moral law). A human action underlies moral principles when she is not based on personal "Neigungen" (feelings), but on the "Pflicht" (duty) to adhere to the "Sittengestz". Personal interests as subjective foundations of human actions are based on non-rational feelings. Duty is universal and should be the same for all human beings. The non-empirical foundation for human actions is the "Achtung" (respect) for the moral law. The moral law as opposed to the subjective (personal) "Maxime" of human actions has universal validity for all mankind. Kant's Ethics centers in his categorical imperative (Kategorischer Imperativ), or absolute moral law, which he first put forward in his Grundlegung zur Metaphysik der Sitten (GMS, 1785 CE) and further develops in his Kritik der praktischen Vernunft (KpV). Kant needed three postulates in order to found his moral reasoning and thereby created a window into the noumenal world. For Kant the postulates of practical reason are freedom, immortality and the existence of God. Free will is the foundation of moral behavior. Immortality enables the endless fulfillment of the moral law. God guarantees morality and its consequences. The categorical imperative was introduced in the Grundlegung zur Metaphysik der Sitten (1785) in which he argues for an a priori basis for morality. The categorical imperative as 'Universalisierungsformel' puts it "Handle nur nach derjenigen Maxime, durch die du zugleich wollen kannst, daß sie ein allgemeines Gesetz werde" (GMS, AA IV, 421), as opposed to the hypothetical or conditional imperative (the rules of skill and the counsels of prudence). Another way in which Kant put forward the categorical imperative, was in the 'Selbstzweckformel': Handle so, dass du die Menschheit sowohl in deiner Person, als in der Person eines jeden anderen jederzeit zugleich als Zweck, niemals bloß als Mittel brauchst(GMS, 1900, AA IV, 429). Another way to put it was the 'Reich-der-Zwecke-Formel': "Demnach muß ein jedes vernünftige Wesen so handeln, als ob es durch seine Maximen jederzeit ein gesetzgebendes Glied im allgemeinen Reiche der Zwecke wäre." (GMS,1900, AA IV, 438). And another way to put is was the 'Naturgesetzformel': "Handle so, als ob die Maxime deiner Handlung durch deinen Willen zum allgemeinen Naturgesetze werden sollte." (GMS,1900, AA IV, 421)
(see also Immanuel Kant's Moral Theory, Roger J. Sullivan, Cambridge University Press, 1989 and Grundlegung zur Metaphysik der Sitten, Immanuel Kant, Ausgabe der Preußischen Akademie der Wissenschaften, Berlin, 1900 and Kritik der praktischen Vernunft, Immanuel Kant, Ausgabe der Preußischen Akademie der Wissenschaften, Berlin, 1900).

His Kritik der Urteilskraft (Critique of the Power of Judgment) considered the concepts of beauty and purposiveness as a bridge between the sensible ("Natur als Erscheinungswelt") and the intelligible worlds ("Freiheit"). The Kritik der Urteilskraft is divided into two main sections, the Critique of Aesthetic Judgment and the Critique of Teleological Judgment. The "Urteilskraft" must overlap both the Understanding (which operates from within a deterministic framework) and Reason (which operates on the grounds of freedom). In the Critique of Aesthetic Judgment, Kant discusses the four possible "reflective judgments": the agreeable, the beautiful, the sublime, and the good. The agreeable is a purely sensory judgment, while the good is essentially a judgment that something is ethical.The beautiful and the sublime occupy a space between the agreeable and the good. They are what Kant refers to as "subjective universal" judgments. The beautiful expresses itself in a "Geschmacksurteil" and brings fort a feeling of "interessenlosen Wohlgefallens". Kant distinguishes between "bestimmender" (determinative) and "reflektierender" (reflective) judgements. In reflective judgment man seeks to find unknown universals (a posteriori) for given particulars; whereas in determinative judgment, we just subsume given particulars under universals that are already known (a priori). Reflective judgement is in addition divided in 'Aesthetic Judgment' and 'Teleological Judgment'. 'Aesthetic Judgment' deals with the subjective goal, while 'Teleological Judgment' dieals with the objective goal, whithout applying a metaphysical goal. In the the Critique of Teleological Judgment writes about the biological as teleological, claiming that there are things, such as living beings, whose parts exist for the sake of their whole and their whole for the sake of their parts. By considering nature as a system existing for the sake of and from its parts, bridges the gap between Nature and Freedom.

In the 1780s and 1790s, Kant's work would lead to the German idealism of Johann Gottlieb Fichte (1762-1814 CE), Friedrich Wilhelm Joseph von Schelling (1775-1854 CE) and Georg Wilhelm Friedrich Hegel (1770-1831 CE).

Hermann Samuel Reimarus (1694-1768 CE) as a philosopher put forward Deism, the doctrine that human reason can arrive at a knowledge of God and ethics from a study of nature and our own internal reality, thus eliminating the need for religions based on revelation.

Moses Mendelssohn (1729-1786 CE)

The Haskalah, or Jewish Enlightenment, was an intellectual movement in Europe that lasted from approximately the 1770s to the 1880s. The Haskalah was inspired by the European Enlightenment but had a Jewish character. Literally, Haskalah comes from the Hebrew word sekhel, meaning "reason" or "intellect" and the movement was based on rationality. It encouraged Jews to study secular subjects, to learn both the European and Hebrew languages, and to enter fields such as agriculture, crafts, the arts and science. The maskilim (followers of the Haskalah) tried to assimilate into European society in dress, language, manners and loyalty to the ruling power. The example of Moses Mendelssohn (1729-1786 CE), served to lead this movement, which was also shaped by Aaron Halle-Wolfssohn (1754-1835 CE) and Joseph Perl (1773-1839 CE). Gotthold Ephraim Lessing (1729-1781 CE) modelled the character of Nathan in his play Nathan der Weise to a large part after his lifelong friend, Moses Mendelssohn. In most of Western Europe, the Haskalah ended with large numbers of Jews assimilating. Many Jews stopped adhering to halakha (Jewish law). The struggle for emancipation in Germany awakened some doubts about the future of Jews in Europe and eventually led to both immigration to America and Zionism.

The Enlightenment was followed by a Counter-Enlightenment movement with thinkers such as Edmund Burke (1729-1797 CE), Joseph de Maistre (1753-1821 CE) and Louis de Bonald (1754-1840 CE). The movement arose primarily in late 18^th and early 19^th century Germany against the rationalism, universalism and empiricism commonly associated with the Enlightenment. Johann Georg Hamann (1730-1788 CE) was one of its proponents. What unites all who oppose the Enlightenment's is a rejection of what they consider to be the Enlightenment's perversion of reason: the distorted conceptions of reason of the kind each associates with the Enlightenment in favour of a more restricted view of the nature, scope and limits of human rationality.

Jean-Jacques Rousseau (1712-1778 CE) was a seminal figure in initiating reaction against the Enlightenment. Rousseau rejected the tyranny of Reason and advocated the return to nature and the revival of inner feeling. On the one hand, Rousseau was a product of the 18th century Europe in that Rousseau with faith in the human dignity and intelligence was the philosophical father of the French Revolution. Its motto was to return to nature, regaining the natural rights of "liberty, equality and fraternity". The nature here stipulated is the nature without corruption, the nature of naivety, the purity of the natural humans. The Du contrat social ou Principes du droit politique (1762) was one of the most influential publications in the social-political philosophy which was being developed at the time. While Montesquieu (1689-1755 CE) dealt with the political institutions prevalent in the time, Rousseau was concerned about the Ideal conditions and the principles of what the government ought to be. The ultimate source of the power of the civil state consists in the general will (la volonté générale). However, this general will is to be distinguished from the will of all (la volonté de tous). The will of all is the aggregate totality of all the individuals' wills each of which seeks each individual's personal profit. The general will aims, as the will of all people, at the happiness of everybody in the society. Each of the members of the society loses the freedom as the natural right, in stead he or she gains the civil freedom determined by the general will. And under the civil laws, each individual is guaranteed its right for property and the right for equality. The genuine possessor of the right of governance is the subject, whereby the civil law is the expression of the general will the sole object or purpose of which is the establishment and maintenance of freedom and equality. In the genuine civil state, the people are to be forced to be free.

Immanuel Kant was moved by Rousseau's work Émile ou De l'éducation (1762) on education. In Émile Rousseau seeks to describe a system of education that would enable the natural man he identifies in Du contrat social ou Principes du droit politique (1762) to survive corrupt society. The French revolution was motivated by the philosophical ideas advanced by Rousseau. Robespierre (1758-1794 CE) made his system of Convention (National Assembly) on the basis of the principle of Rousseau's Contrat social. The Sturm und Drang Movement in Germany was also influenced by Rousseau. Johann Georg Hamann (1730-1788 CE) was the most important philosopher of this movement which also influenced Goethe and Schiller.

The Roman Catholic Church did not approve the philosophical developments of the Enlightenment. The ultramontane point of view of the Church was supported by the Society of Jesus which first came into being as the Catholic fortress against the Reformation. The Society of Jesus rose to the occasion of defending the position of the Church against the reforms requested by the philosophers of the Enlightenment and the politicians. As a result the Jesuits were expelled from Brazil (1754), Portugal (1759), France (1764), Spain and its colonies (1767) and Parma (1768). Due to the growing opposition against the Society of Jesus, the order was suppressed by Pope Clement XIV (1705-1774 CE) with the papal brief Dominus ac Redemptor Noster (21 July 1773). The order remained active in Prussia and Russia, where Catherine the Great had forbidden the papal decree to be executed. Pope Pius VI would grant formal permission for the continuation of the Society in Russia and Poland. Pope Pius VII (1742-1823 CE) would restore the Society of Jesus on 7 August 1814, with the papal bull Sollicitudo omnium ecclesiarum.

Enlightenment
Haskalah
European Enlightenment - Richard Hooker
The Enlightenment: Nine Theses
Catholic Enlightenment
Twilight for the Enlightenment? - Donald Kennedy (2005)
Early Modern Texts
The Age of Reason

Pierre Bayle - (1647-1706)
Jean Meslier - (1664-1729)
Superstition in all ages - Jean Meslier (1729)
Le Testament de Jean Meslier - Jean Meslier (1729)
Giovanni Battista Vico - (1668-1744)
George Berkeley - (1685-1783) "esse est percipi"
Voltaire (1694-1778)
Voltaire - integral
Pierre Louis Moreau de Maupertuis -(1698-1759)
Julien Offray de La Mettrie - (1709-1751)
Du Contrat social ou Principe du droit politique - Rousseau (1762)
Denis Diderot - (1713-1784)
L'Encyclopédie, ou Dictionnaire Raisonné des Sciences, des Arts et des Métiers
Étienne Bonnot de Condillac - (1714-1780)
Baron d'Holbach - (1723-1789)
Immanuel Kant - (1724-1804)
Immanuel Kant - (1724-1804)
Beantwortung der Frage: was ist Aufklärung ? - Immanuel Kant
Immanuel Kant - Complete works
Kritik der reinen Vernunft - Immanuel Kant - (1781, 1. Auflage)
Prolegomena zu einer jeden künftigen Metaphysik die als Wissenschaft wird auftreten können - Immanuel Kant - (1783)
Kritik der reinen Vernunft - Immanuel Kant - (1787, 2. Auflage)
Kritik der praktischen Vernunft - Immanuel Kant - (1788)
Kritik der Urteilskraft - Immanuel Kant - (1790)
Gotthold Ephraim Lessing - (1729-1781)
Nathan der Weise - G.E. Lessing
Edward Gibbon - (1737-1794)
The History Of The Decline And Fall Of The Roman Empire - Edward Gibbon
Thomas Paine - (1737-1809)
The Age of Reason - Thomas Paine
Thomas Paine National Historical Association

The 19^th century took the radical notions of self-organization and intrinsic order from Johann Wolfgang von Goethe (1749-1832 CE) and Kantian metaphysics, and proceeded to produce a long elaboration on the tension between systematization and organic development. The concept of self-organization is the spontaneous emergence of order out of primordial chaos, which refers to the old Greek idea that cosmos (κόσμος) emerged from chaos (χάος) or in Latin: "ordo ab chao". Immanuel Kant (1724-1804 CE) in his Kritik der reinen Vernunft (1781) introduced self-organization in modern philosophy. He applied it to processes of organic nature and in his theory of the formation of the planetary system. Friedrich von Schelling (1775-1854 CE), one of the German idealists, would extend the concept to inorganic nature and to the complete evolution of the universe, from the primordial beginnings of matter up to the origin of life and human mind. Since Immanuel Kant (1724-1804 CE), modern philosophy would (mainly) reject the dogmatic metaphysics of the Rationalists that promised supersensible knowledge and try to deal with the limitations of Empiricism. The rigid rationalism of the Enlightenment made room for philosophical vitalism and anti-rationalism. The Will or matter became the driving force, not reason. The mystery of the Will or material dialectics replaced the mystery of God
(see also Mechanism Versus Vitalism As a Philosophical Issue, Walter T. Marvin, The Philosophical Review, Vol. 27, No. 6 (Nov., 1918), pp. 616-627).

Johann Gottlieb Fichte (1762-1814 CE) and Georg Wilhelm Friedrich Hegel (1770-1831 CE) were philosophers of German idealism. Idealism deals with the relation between epistemological idealism and ontological idealism.

Hegelian philosophy had a profound influence on German philosophy and his follower were the Hegelians. The Hegelians can be roughly divided into the politically and religiously radical 'left', or 'young', Hegelians and the more conservative 'right', or 'right'Hegelians. The Young Hegelians reacted to and wrote about the legacy of Hegel. The Right Hegelians followed Hegel in believing that the dialectic of history had come to an end. The Young Hegelians put the focus on Hegelian Reason and Freedom as the guiding forces of history and the fact that the dialectic was not (yet) complete. Both accepted historical development as a philosophical idea which put man in his historical context at the center of historical philosophical development instead of God. Their belief in the inevitable progress of human philosophical development replaced the idealistic metaphysical philosophy of rationalisms and religion. Well known Young Hegelians are Friedrich von Schelling (1775-1854 CE), Ludwig Feuerbach (1804-1872 CE) and Karl Marx (1818-1883 CE). The Young Hegelian David Friedrich Strauß (1808-1874 CE) was a pioneer in the historical investigation of Jesus and he caused a scandal with his Das Leben Jesu, kritisch bearbeitet (1835-1836 CE). He did not deny that Jesus existed, but he did argue that the miracles in the New Testament were mythical additions with little basis in actual fact. His interpretation created a third way between the 'rationalists' and the 'supernaturalists'. Bruno Bauer (1809-1882 CE) was a leader of the Left-Hegelian movement, developing a republican interpretation of Hegel. He already described religion as a form of alienation. John McTaggart (1866-1925 CE) and Francis Herbert Bradley (1846-1924 CE) were British Idealists.
(see also The Young Hegelians and Karl Marx, David McLellan, Gregg Revivals, 1993 and David Friedrich Strauss and his place in modern thought, Richard S. Cromwell, R. E. Burdick, 1974).

Several philosophers would distance themselves form Hegelianism. Arthur Schopenhauer (1788-1860 CE), Søren Kierkegaard (1813-1855 CE) and Friedrich Wilhelm Nietzsche (1844-1900 CE) would oppose Hegel. Jeremy Bentham (1748-1832 CE) was one of the founders of utilitarianism, which evaluates actions based upon their consequences. Charles Sanders Peirce (1839-1914 CE) was the founder of pragmatism. As with the 18^th century, it would be developments in science that would arise from, and then challenge, philosophy: most importantly the work of Charles R. Darwin (1809-1882 CE) who published his On the Origin of Species in 1859, which was based on the idea of organic self-regulation found in philosophers such as Adam Smith (1723-1790 CE), but fundamentally challenged established conceptions. Laws of self-organization put certain limits of arbitrariness on nature in choosing possible paths of evolution. As a philosophical consequence they provide developmental theories with a materialistic dialectical foundation. While the physics of Aristotle had lost its leading role with the heliocentrism of Nicolaus Copernicus (1473-24 May 1543 CE), Darwinism would also change the static idea of biology which was accepted since Aristotle and by Christianity. The aspect of temporal change and historical development in biology would also change the Newtonian idea of the perfect mechanical and static universe and nature. The increasing age of the earth would also have an impact on the place and role of man and civilization. Scientific discoveries increasingly caused philosophical and theological problems. Gottlob Frege (1848-1925 CE) developed a new system of logic, which was capable to shed the burden of Aristotelian logic which hat dominated Western philosophy. The antagonism between realism and nominalism changed into the antagonism between realism and idealism in modern philosophy.
(see also German Philosophers: Kant, Hegel, Schopenhauer, Nietzsche, Roger Scruton, Oxford University Press, 1997 and The Modern Philosophical Revolution: The Luminosity of Existence, David Walsh, Cambridge University Press, 2008 and The Philosophy of Gottlob Frege, Richard L. Mendelsohn, Cambridge University Press, 2005 and Schelling’s Concept of Self-Organization, M.-L. Heuser-Keßler, Volume 69 of the series Springer Proceedings in Physics pp 395-415 and Arbitrariness in nature: synergetics and evolutionary laws of prohibition, Hermann Haken and Helena Knyazeva, Journal for General Philosophy of Science 31, 2000, pp. 57-73 and Erwin Schrödinger’s World View: The Dynamics of Knowledge and Reality, Johann Götschl, Springer Science & Business Media, 2012, p. 83).

Johann Gottlieb Fichte (1762-1814 CE) developed his own version of Kantian transcendental idealism, based upon the bare concept of subjectivity. His most important work is the Grundlage der gesammten Wissenschaftslehre. Fichte rejected the Kantian idea of the unknowable 'Ding an Sich' and developed the phenomenology of consciousness.
(see also Central Works of Philosophy V3: Nineteenth Century, Volume 3, John Shand, Routledge, 2015, p. 43 and History of Philosophy: Fichte to Nietzsche, Frederick Charles Copleston, Paulist Press, 1963, p. 43).

Georg Wilhelm Friedrich Hegel (1770-1831 CE) was a German philosopher. Hegel rejected the Kantian limitation that reason could not surpass perception or the phenomenal world. He developed the concept of a logically-necessitated teleological course of history and philosophy. Philosophical truth (Spirit, 'Geist') would emerge out of historical development in a 'Phänomenologie des Geistes' or the three-stage dialectical life of Spirit or Mind. Hegel would combine the universalist dimensions of Kant's transcendental program with the culturally contextualist conceptions of Romanticism, resulting in his conception of the emergence (surfacing) of a universal spirit within the context of time. 'Absolute Knowing' becomes manifest in time. His major works are the Phänomenologie des Geistes (1807) and Wissenschaft der Logik, I, Wissenschaft der Logik, II (1812, 1813), Enzyklopädie der Philosophischen Wissenschaften im Grundrisse (1817) and Grundlinien der Philosophie des Rechts (1821). A critical philosophy was required to scrutinize human knowledge. Every philosophy, according to Hegel, had presupposed a complete separation between the content of cognition (the world of objects, held to be entirely independent of thought for their existence), and the form of cognition (the thoughts about these objects, which by themselves are pliable, indeterminate and entirely dependent upon their conformity to the world of objects to be thought of as in any way true). This unbridgeable gap found within the science of reason was, in his view, a carryover from everyday, phenomenal, unphilosophical consciousness. Hegel in his philosophy wanted to extinguish this opposition within human consciousness: "Das Wahre ist das Ganze": Idee, Natur und Geist. Hegel attempted a reconciliation of man with reality, where the development of the subject happens through and in connection with objective reality. Man is part of reality and expresses (manifests) himself in reality, which leads to a positive view on labor. The Critical Philosophy of Hegel as in Empiricism assumes that experience affords the one sole foundation for cognitions; which however it does not allow to rank as truths, but only as knowledge of phenomena
(see also Hegels Phänomenologie des Geistes. Ein dialogischer Kommentar, Pirmin Stekeler, Meiner Verlag, 2014, p; 224).

In his Phänomenologie des Geistes he describes the master-slave dialectic on the development of self-consciousness out of consciousness. Hegel was influenced by the Kantian concept of 'transcendental unity of apperception' or the transcendental faculty or capacity for judging in accord with a rule, for applying concepts. A subject lives within and perceives a world of objects in which it perceives itself as a unit. By means of dialectical progress consciousness progresses towards self-consciousness, which Hegel illustrates with the master-slave dialectic . Knowledge evolves through consciousness, self-consciousness, reason, Geist, religion up to 'Absolute Knowing' which transcends the individual
(see also Still reading Hegel: 200 years after the phenomenology of spirit, Edmundo Balsemão Pires, Coimbra University Press, 2009, p. 13).

Hegel in his Wissenschaft der Logik developed his dialectical metaphysics in which thought and being constitute a single and active unity. His logic is a critical and "dialectical" framework for a dynamic and evolving ordering of knowledge (Abstract-Negative-Concrete): Subjektivität (Begriffe) - Objektivität (Realität) - Idee. The word dialectic itself originated in Ancient Greece, and was made popular by Plato (429-347 BCE) in the Socratic dialogs. The dialectical method takes the form of a dialog between two or more people holding different points of view about a subject, who wish to establish the truth of the matter by dialog, with reasoned arguments. Dialectics is different from debate, wherein the debaters are committed to their points of view, and mean to win the debate, either by persuading the opponent, proving their argument correct, or proving the opponent's argument incorrect. Hegel in his philosophy stated that reality is shaped through and through by mind and, when properly understood, is mind. Thus, according to Hegel, ultimately the structures of thought and reality, subject and object, are identical. Immanuel Kant (1724-1804 CE) in his Kritik der reinen Vernunft on 'Transcendental Dialectic', discussed how pure reason should not be used. According to Kant, the rational faculty is plagued with dialectic illusions as man attempts to know what can never be known beyond the phenomenal world and therefore metaphysics is 'empty'. Hegel however rejected the Kantian limitation that reason could not surpass perception or the phenomenal world and put forward somewhat of a return to a dogmatic and more religiously inspired philosophy against which Kant had reacted. For Hegel the limitations which Kant put forward only apply to cognition ('Erkenntnis'), which is limited by the faculty of sensibility as opposed to the noumena known purely conceptually. Kant got stuck on antinomies, while Hegel's dialectic or logic was meant to lead to a sublation ('aufhebung') of antinomies. Every concept is a synthesis of antinomies where the contradictions have been sublated ('aufhebung'). Knowledge progresses by concecutive sublation of contradictions. Every concept generates its own negation and by resolving this, knowledge grows and progresses up to an increasingly higher level. The negation of a concept is the concept which defines something beyond the limitations of the first concept. When combining these concepts the limitations of both concepts transcend into a new more complete concept ('aufhebung'). Sublation is the ending of a step in a logical process, yet at the same time it is a new beginning from a new point of view
(see also The Future of Hegel: Plasticity, Temporality, and Dialectic, Catherine Malabou, Psychology Press, 2005, p. 156 and Picturing Hegel: An Illustrated Guide to Hegel's Encyclopaedia Logic, Julie E. Maybee, Rowman & Littlefield, 2009, p. 239).

For Hegel his logic starts with 'Pure Being' and evolves up to 'Pure Knowing', which is his 'Doctrine of Being'. Pure Knowing itself is the final state achieved in the historical self-manifestation of Geist (Spirit/Mind). First we have 'Pure Being' (pure indeterminateness) which is also 'Pure Nothing' (complete emptiness), but which is thought of as the opposite of 'Pure Being'. When the contradiction between 'Pure Being' evolves into 'Pure Nothing', we have Becoming which can be Coming-to-Be and Ceasing-to-Be. Here we have a philosophy of becoming, which reminds of Heraclitus (ca. 535-ca. 475 BCE). Becoming leads to Determinate Being as the sublation between 'Pure Being' and 'Pure Knowing'. The system continues, in the end leading to 'Pure Knowing'
(see also Picturing Hegel: An Illustrated Guide to Hegel's Encyclopaedia Logic, Julie E. Maybee, Rowman & Littlefield, 2009, p. 50).

Friedrich Wilhelm Joseph von Schelling (1775-1854 CE) in his work Über die Natur der Philosophie als Wissenschaft (1821) would postulate a meta-philosophy of which every particular philosophy is only part of and which exists outside and beyond the rational capabilities of man. In this work he wrote: 'Was Dante an der Pforte des Infernum geschrieben sein läßt, dies ist in einem andern Sinne auch vor den Eingang zur Philosophie zu schreiben: "Laßt alle Hoffnung fahren, die ihr eingeht"'. For Schelling there is no ascent to the absolute from the finite, i.e., no cosmological demonstration of God's reality
(see also Schelling's Philosophy of Identity and Spinoza Ethica more geometrico, Michael Vater, Marquette University). Schelling insisted on the need not to limit our conception of nature to what can be objectified by scientific methods. This proposition inevitably leads to obscurantism, because the meta-philosophy, although perfect and absolute remains out of reach of rationality (anything goes as rational discussion becomes impossible). For Schelling however reason's incapacity to ground itself should not lead to an abandonment of rationality. In his work Darstellung meines Systems der Philosophie (1801), Bruno oder über das göttliche und natürliche Prinzip der Dinge (1802) and System der gesammten Philosophie und der Naturphilosophie insbesondere (1804), Schelling dealt with the dichotomy of Natural Philosophy (Naturphilosophie) and Metaphysics (Transzendentalphilosophie) which he wanted to unify into one philosophical system (1801-1809): Identity Philosophy (Identitätssystem). Schelling's philosophy of identity results from his rejection of the unbridgeable gap between subject and object: "the knower and that which is known are the same". Schelling's work from his middle period (1809-1827) is usually referred to as the philosophy of the Ages of the World, as he put forward in Die Weltalter (unfinished 1809-1827). The 'Weltalter' philosophy is an attempt to explain the emergence of an intelligible world at the same time as coming to terms with mind's inextricable relation to matter. The theory is based on the antagonisms between opposing forces which constitute the 'ages of the world', the past, present, and future (cfr. the law of contradiction).

Ludwig Feuerbach (1804-1872 CE) was an associate of Left or Young Hegelian circles, and was politically liberal, an atheist and a materialist. His most important work is Das Wesen des Christentums (1841 CE), in which he postulated that God is the outward projection of a human's inward nature. He uses the term "species-being" (Gattungswesen) in Das Wesen des Christentums for the essence of humanity, what makes us human and what makes us distinct from animals. From this concept of being part of a species we develop our sense of individuality. For Feuerbach people alienate their essential being by attributing their human qualities to a god who is then worshiped on account of these qualities. The philosophy of Feuerbach consisted in a new interpretation of religion's phenomena, giving it an anthropological explanation. Feuerbach developed a materialistic humanism and an ethics of human solidarity
(see also Feuerbach and the Interpretation of Religion, Van A. Harvey, Cambridge University Press, 1997, p. 104).

Karl Marx (1818-1883 CE) was one of the Young Hegelians. Together with Friedrich Engels (1820-1895 CE) he developed dialectical materialism which stated that the higher level of existence emerges from and has its roots in the lower as opposed to Hegel. Marx developed a theory of alienation as an alienation from the self. His most well known works are Die heilige Familie oder Kritik der kritischen Kritik (1845), Misère de la philosophie (1847 CE), Manifest der kommunistische Partei (1848), Ökonomisch-philosophische Manuskripte (1844 CE), Der achtzehnte Brumaire des Louis Napoleon (1852 CE), Die deutsche Ideologie (1845-1846 CE), Zur Kritik der Politischen Ökonomie (1859), Grundrisse der Kritik der politischen Ökonomie (1857-1858 CE), Das Kapital (1867-1894 CE).

Marx developed a metaphysical materialism opposed to the idealism of Hegel and "stellt sie „vom Kopf auf die Füße“" or puts Hegelian dialectic "on its feet". He rejected the idealistic foundation of Hegelian philosophy but kept the historical perspective. He developed a dialectic materialism on the evolution of the natural world and the emergence of new qualities of being at new stages of evolution. For Marx the world of the concrete shapes socioeconomic interactions and those in turn determine sociopolitical reality. From this he developed a theory why the world is the way it is, but also of which actions people should be taken to make it the way it ought to be. His materialism asserted the primacy of the material world where matter precedes thought. He developed a theory of base and superstructure. The base comprises the forces and relations of production which determines the superstructure which includes its culture, institutions, political power structures, roles, rituals, and state. The forces of production refer to the combination of the means of labor (tools) with human labor power which includes labor itself and knowledge. The institutions and political power structures at any given moment intend to maintain the status quo but change in a dialectical process in which Marx distinguishes five stages. The latest stage would be communism where the controlling superstructure will no longer be needed to conceal the true relations between the forces of production. The transition from capitalism to communism would happen by means of a revolution when capitalism no longer is capable to control the conflicts it causes within society
(see also Dialectical Materialism, Viktor Grigorʹevich Afanasʹev, International Publishers, 1987).

Marx develops a theory of human nature in which he uses the term "species-being" (Gattungswesen) of Ludwig Feuerbach (1804-1872 CE) to develop his own theory of human nature. Marx writes of the importance of social relations for human nature and man as a homo faber and the important role of labor. The problem of self-realization is the relationship and conflict between essence and existence. Man by means of labor as a productive process, realizes his own essence and returns to his own essence. Activity not passivity leads to self-realization. The development of self-consciousness for Marx has three stages, first there is primitive self-consciousness, then self-alienation and finally self-realization. Self-realization as a process of productive relatedness and oneness between man and nature. The three stages of the development of self-consciousness are related to three historical periods. The first stage is the primitive stage of man living a life dominated by nature and nature is not yet an 'object'. The second stage is the stage of 'private property' which also separates man from nature. Finally man reaches the stage of communism in which he completely dominates nature and private property is no longer needed. The existence of man now unites with his essence or "species-being" (Gattungswesen). His labor is now free from the alienation of the second stage with its private property, which dominates capitalism. Human labor in society transforms the world and defines his "species-being" (Gattungswesen). Marx opposed the liberal concept of the homo economicus which emphasized private property as in An Inquiry into the Nature and Causes of the Wealth of Nations of Adam Smith (1723-1790 CE). For Marx private property leads to self-alienation as it acts as a fetish. Modern economy based on money leads to ultimate alienation as money itself becomes the ultimate fetish (Zur Judenfrage 1844 CE): "Das Geld ist der allgemeine, für sich selbst konstituierte Wert aller Dinge. Es hat daher die ganze Welt, die Menschenwelt wie die Natur, ihres eigentümlichen Wertes beraubt. Das Geld ist das dem Menschen entfremdete Wesen seiner Arbeit und seines Daseins, und dies fremde Wesen beherrscht ihn, und er betet es an.". Fetishism refers to the way that people project themselves subjectively onto the world of man-made objects, thereby alienating parts of his own Self into objects. The concept of a fetish had been first used by Charles de Brosses (1709-1777 CE) in his Du culte des dieux fétiches ou Parallèle de l'ancienne religion de l'Egypte avec la religion actuelle de Nigritie ((1760 CE). Charles de Brosses described fetishism as the worship of an object per se, not as a representation of another power and hence as a confusion of a divinity with its sign, but as a material incarnation and even as a real source of power. Immanuel Kant (1724-1804 CE) in his philosophy of religion had related fetishism to a lack of judgment, an aesthetic incapacity and for substituting superstitious rituals for morally virtuous conduct. For Ludwig Feuerbach and Marx religion became a false outward projection of the essence of man upon an external self-created God. Human perfection is alienated from the Self and projected into a transcendent God. Religion alienates man from his "species-being" (Gattungswesen). This lead Marx to formulate his version of the Kantian categorical imperative: "The criticism of religion ends with the teaching that man is the highest being for man, hence with the categorical imperative to overthrow all relations in which man is a debased, enslaved, forsaken, despicable being ..."
(see also Marxism and Alienation, Nicholas Churchich, Fairleigh Dickinson Univ Press, 1990, p. 105 and Kopstukken filosofie Marx, Peter Singer, Lemniscaat Publishers, 1999, p.32).

The 19^th century would also include Arthur Schopenhauer's (1788-1860 CE) concept of the will as in his Die Welt als Wille und Vorstellung (1818). In Die Welt als Wille und Vorstellung Schopenhauer discusses what is and is not of value in existence, the striving and pain of the human condition and the possibility of deliverance from it. For Schopenhauer the world (eveything which exists) can be seen as 'Vorstellung' (phenomena) and 'Wille' (noumenal). The entire phenomenal world, as well as each of the individual items in it, is a representation of Will. Historical development was the result of a blind Will acting without rational goal. He was among the first modern philosophers to contend that at its core, the universe is not a rational place. The entire world is the representation of a single (untamed) Will, of which our individual wills are phenomena like the droplets of a waterfall which create a rainbow. Schopenhauer holds that all nature, including man, is the expression of an insatiable will to life. The will is related to the Kantian concept of the 'Ding an Sich'. The human will, for Schopenhauer, is our one window to the world behind the representation or the 'Ding an Sich'. On the other hand there is the way man sees the world as representation 'Vorstellung' or rational
(see also Schopenhauers existentielle Metaphern im Kontext seiner Philosophie, Matthias Rühl, LIT Verlag Münster, 2001, p. 64).

The phenomenal aspect appears to our experience, but does not lead us to its essence. We can only turn into ourselves to discover our true essence, which is the Will our central core. What we encounter in ourselves is pure life drive or pure Will. This pure energy, drive, urge or 'Wille' is at the center of all life and not only our life. The inner nature of every thing, the 'Ding an Sich' of each individual thing as well as of the whole, is Will. The Will which evolves into living things, develops consciousness in order to help will achieve what it 'wants'. Will has evolved (just enough) mind to help will meet its own needs, and most people have only as much mind as is necessary to help their will meet its needs and interests. For Schopenhauer this life is full of suffering and we are living in a world of illusion. What can we do about it? Most people are not aware of the real situation in the world and so for them there is no hope at all according to Schopenhauer. They suffer as long as long as they remain mere will-filled subjects. For those who are aware of the real situation in the world (a world of suffering, will, and illusion) there is hope. One way out is in the encounter with the beautiful or aesthetic contemplation, the other being asceticism and religion. Some people may have an excess of consciousness, more mind than is necessary for simply meeting their will's needs, which allows these people to "see" more than others can see. They achieve aesthetic contemplation, which for Schopenhauer relates to genius. The experience of (true) aesthetic contemplation takes them temporarily out of our will-filled self. This relates somewhat to Plato's aesthetics and theory of beauty. Another way towards liberation is asceticism, or self-denial, which is the practice of turning the will against itself as a way of extinguishing its power. In order to end suffering permanently one has to practice denying the will what it wants, which is asceticism or self-denial. Asceticism from the Greek ἄσκησις or Latin 'agere contra' (acting against) meaning self denial. In the face of a world filled with endless strife man, through asceticism, ought to minimize his natural desires (Verneinung) for the sake of achieving a more tranquil frame of mind and a disposition towards universal beneficence. This shows the influence of Eastern philosophy, such a Buddhism, on Schopenhauer. On religion Schopenhauer relates to compassion, or fellow-feeling, which is the basis of ethics. Moral behavior consists of an intuitive recognition that we are all manifestations of the Will. Compassion is also a way to free ourselves from the wheel of Ixion of the Will and to reach complete self-denial like in Nirvana (निर्वाण)
(see also The Stanford Encyclopedia of Philosophy, Arthur Schopenhauer, Edward N. Zalta (ed.), Robert Wicks, Spring 2015 Edition and A Companion to Schopenhauer, Bart Vandenabeele John Wiley & Sons, 2015 and Asceticism, Vincent L. Wimbush, Richard Valantasis, Oxford University Press, 2002, p. 590 and Schopenhauer: The World as Will and Representation:, Volume 1, Christopher Janaway, Cambridge University Press, 2010, p. xxxi).

The Danish philosopher Søren Kierkegaard (1813-1855 CE) took philosophy in a new direction by focusing less on abstract concepts and more on what it means to be an existing individual. He developed an anti-Hegelian philosophy which does not put history or a system at the center like Hegel did, but Kierkegaard put the individual and his existence at the center of his philosophy. Important works are Either/Or (Enten-Eller), Fear and Trembling (Frygt og bæven) and Repetition (Gjentagelsen). He emphasized the importance of the individual existence over the "numeric masses" of the system. His focus on subjectivity made him emphasize subjective (personal) truth over objective (impersonal) truth: "Truth as Subjectivity". In his work he also put forward a new view on Christianity, as a reaction against an criticism of organized state religion. Kierkegaard in his work dealt with Christian love and life as a task or destination. He developed a three stage view on human development and put forward that the individual passed through three stages on the way to becoming a true self: the aesthetic, the ethical, and the religious. In the aesthetic life, one is ruled by passion, while in the ethical life, one is ruled by societal regulations. Finally in the religious life, one is ruled by total faith in God. The first aesthetic stage is the realm of sensory experience and pleasures. The aesthetic life is defined by pleasures, and to live the aesthetic life to the fullest one must seek to maximize those pleasures. The aesthetic life is primarily a stage of self-gratification. The second stage is the ethical life adhering to the social rules that govern how a person ought to act. An ethical life allows diverse people to coexist in harmony and brings individuals to live for the good of society. The third stage for Kierkegaard is the religious life, which he considers to be the highest plane of existence. Kierkegaard divides the religious stage into Religiousness A and B. Religiousness A (Religiøsitet A) applies to the individual who feels a sense of guilt before God, which is a religiousness of immanence. Religiousness B (Religiøsitet B) is transcendental and consists of a radical conversion in a qualitative leap of faith beyond the boundaries and limitations of reason (springet til det religiøse stadie). The relationship with God is exclusively personal and he criticized the Christian Church for what he saw as its interference in the personal spiritual quest each true Christian must undertake. In order to get to the third stage it requires a qualitative leap of faith as reason is not capable to bridge the gap, which leads to fideism. The qualitative leap of faith has no gradations or movements (the quantitative) or rational basis as it is sudden (qualitative) and it is not out of thoughtlessness, but out of volition. According to Kierkegaard essential truth is far beyond our comprehension to the extent that we cannot approach it objectively (infinite qualitative distinction), and therefore it appears to us in the form of a paradox which we cannot deal with by reason but only with a leap of faith where man becomes a knight of faith. His work provided impetus for many 20^th century philosophical movements, including existentialism. Existentialists state that the individual is solely responsible for giving his or her own life meaning and for living that life passionately and sincerely, in spite of many existential obstacles and distractions including despair, angst, absurdity, alienation, and boredom
(see also The SPCK Introduction to Kierkegaard, Peter Vardy, SPCK, 2012 and Søren Kierkegaard, Volume 1, Daniel W. Conway, K. E. Gover, Taylor & Francis, 2002, p. 144).

Friedrich Wilhelm Nietzsche (1844-1900 CE) developed Critical Philosophy to its most radical consequences. Central to his philosophy is the idea of "life-affirmation", which involves an honest questioning of all doctrines that drain life's expansive energies, however socially prevalent those views might be. His most important works are Morgenröte (1881 CE), Die fröhliche Wissenschaft (1882 CE), Also sprach Zarathustra (1883-1885 CE), Jenseits von Gut und Böse (1886 CE), Zur Genealogie der Moral (1887 CE), Der Fall Wagner (1888 CE), Antichrist (1888 CE), Ecce Homo (1888 CE), and Götzen-Dämmerung, oder, Wie man mit dem Hammer philosophiert (1889 CE). In his philosophy he rejected Platonism and Christian morality. In his Die Geburt der Tragödie aus dem Geiste der Musik (1872 CE) he discussed the Apollonian and Dionysian character of Greek culture, where Apollo is the god of reason and the rational, while Dionysus is the god of the irrational and chaos. Socratic rationalism or Appolonism sees life as a disease and opposes the Dionysian existence which constantly seeks to affirm life. They both create an intertwined dialectical pair which embraces chaos (Dionysian) while discovering and seeing the harmony of it (Apollonian) . Only the union of both created ancient Greek Culture, while modern society has lost its connection with the Dionysian aspect of life
(see also Nietzsche: Disciple of Dionysus, Rose Pfeffer, Bucknell University Press, 1972, p. 38 and Nietzsche and Philosophy, Gilles Deleuze, A&C Black, 2006, p. 11).

In his work Götzen-Dämmerung, oder, Wie man mit dem Hammer philosophiert, Nietzsche opposed the classical approach towards universals in philosophy. In Platonic philosophy and its realist derivatives the "True World" became fiction and the imagined world became reality. For Plato or a Christian, the everyday world is a kind of deception, and another immutable world that we fail to see is the true world. Nietzsche opposed the rejection of the "True World" of Plato (424/423-348/347 BCE), who in his Timaeus put forward a distinction between "what always is and never becomes" (universals) and "what becomes and never is" (nature, perceived through sense perception). By making universals more important than nature, Plato and his followers rejected the "True World". Platonism and Christianity say "no" to this world and posit another "true" world behind this one. For Nietzsche, Christianity was merely Platonism for the masses. Nietzsche rejects this Platonic view and he conceives this alternative as saying "yes" to this world of the senses. The Heracliteian world of becoming is the important one, not the illusory Platonic world of being. Part of the acceptance of the world was the concept of the eternal return (Ewige-Wiederkunfts-Gedanke). This universe is all there is, and that it repeats itself endlessly: at the end of time there is the beginning of time, and all happens again exactly as before. There is no escaping this world, no so-called true Platonic world behind this world. If man can say yes to his life, knowing that it will happen forever the same way again and again, knowing there is nothing behind or beyond it, then man will become the Übermensch and live a life of value. No longer such man is a slave to false opinions and illusions but accepts the 'amor fati'
(see also Heidegger, Art, and Postmodernity, Iain D. Thomson, Cambridge University Press, 2011, p. 17).

For Nietzsche, the idea of God was also a postulated universal and part of the "Four Great Errors" of philosophy. In Die fröhliche Wissenschaft (1882 CE) and Also sprach Zarathustra Nietzsche would put forward his "Gott ist tot" idea as part of his rejection of the tradition of postulating transcendent universals (realism). In Der Wille zur Macht, Versuch einer Umwertung aller Werte (The Will to Power, posthumously) Nietzsche claimed that philosophers from Socrates (469-399 BCE) onward had built up a notion of "moral truth" as expressing an objective moral reality. Niezsche credited the Sophists with having attacked this notion: "they postulate the first truth that a 'morality-in-itself', a 'good-in-itself' do not exist, that it is a swindle to talk of 'truth' in this field" , (Der Wille zur Macht, Section 428). In his work Nietzsche tried to break down the distinction Parmenides (early 5^th century BCE) had erected between appearance and reality, which had become the basis for the Aristotelian definition of truth (Correspondence Theory of Truth)
(see also Nietzsche and Philosophy, Gilles Deleuze, A&C Black, 2006, p. 144 and Nietzsche and the Gods, Weaver Santaniello, SUNY Press, 2001, p. 184 and Reading Nietzsche through the Ancients: An Analysis of Becoming, Perspectivism, and the Principle of Non-Contradiction, Matthew Meyer Walter de Gruyter GmbH & Co KG, 2014, p. 63 and Nietzsche's Ontology, Laird Addis, Walter de Gruyter, 2012, p. 104).

Nietzsche criticized the impact of Christianity on morality and made a distinction between master versus slave morality. In his Zur Genealogie der Moral (1887 CE) he develops a theory of the genesis of Christian morality as a 'slave morality'. His historical analysis is a radical attack on these morals, offering a kind of social and psychological account of why they arose. He proposed a revaluation of all values (Umwertung aller Werte), For Nietzsche Christianity inverts nature as it elevates the weak over the strong, exalting that which is "ill-constituted and weak" at the expense of that which is full of life and vitality. In Christianity he weak acted out of resentment, out of a desire to find some way to assert themselves over the great, and that is the source of Christianity and its ethics. Max Stirner (1806-1856 CE) in Der Einzige und sein Eigentum (1845 CE) had criticized the modern world as increasingly dominated by religious modes of thought and oppressive social institutions. His alternative was a radical 'egoistic' life in which individual autonomy might flourish. This would inspire Nietzsche to develop his Nietzschean individualism. Nietzsche rejected metaphysical certainty and postulated a radical perspectivism (Perspektivismus) resembling the 'homo mensura' principle of Protagoras (fl.5th c.BCE) that all ideations take place from particular perspectives. What we perceive as truth is purely a construct of our own mind. As a society we tend to take these 'truths' for granted. The Kantian 'Ding an Sich' is an illusion which man has to outgrow be the power of his will. It brings him to develop an Aristotelian virtue ethics and the concept of the Übermensch living in this world free from the illusion of false morality and metaphysics. The Nietzschean Übermensch resembles the great-souled man or megalopsuchos (μεγαλόψῡχη) of the Nicomachean Ethics which manifests "greatness in every virtue". The Wille zur Macht (will to power) for Nietzsche was the main driving force in humans as the striving to reach the highest possible (virtuous) position in life by "self-overcoming". The Übermensch is capable of making free, conscious choices by means of 'Gay Science' (Die fröhliche Wissenschaft) in accordance with his entire being or will
(see also The Growth of the Liberal Soul, David Walsh, University of Missouri Press, 1997, p. 28 and Nietzsche's Mirror: The World as Will to Power, Linda L. Williams, Rowman & Littlefield Publishers, 2002, p. 1 and Nietzsche and Philosophy, Gilles Deleuze, A&C Black, 2006, p. 46).

The development of science and most notably quantum physics and relativity would have a profound impact on philosophy. Pragmatism would become the philosophy for the relativistic age. Relativity however is not the same as relativism. Charles Sanders Peirce (1839-1914 CE) was the founder of pragmatism. William James (1842-1910 CE) and John Dewey (1859-1952 CE) would also contribute to the deveopment of pragmatism. The pragmatist maxim is a distinctive rule or method for becoming reflectively clear about the contents of concepts and hypotheses: pragmatists clarify a hypothesis by identifying its practical consequences. Pragmatists saw themselves as providing a return to common sense and the facts of experience and, thus, as rejecting a flawed philosophical heritage which had distorted the work of earlier thinkers.

Contemporary Western philosophy is the present period in the history of Western philosophy beginning at the end of the 19^th century with the professionalization of the discipline and the rise of analytic and continental philosophy. It is roughly considered to have started with Ludwig Wittgenstein (1889-1951 CE), who published his famous book the Tractatus Logico-Philosophicus in 1921. Many of the ideas he put forward in the Tractatus were later contradicted or discarded in his Philosophische Untersuchungen published posthumously in 1953.

European Continental philosophy and Anglo-American philosophy both evolved in several ways. Continental philosophy is generally agreed to include phenomenology, existentialism, hermeneutics, structuralism, post-structuralism, post-modernism, post-modernism, deconstruction, French feminism, and critical theory, such as that of the Frankfurt School, the works of Friedrich Nietzsche (1844-1900 CE), Søren Kierkegaard (1813-1855 CE), and most branches of Marxism and Marxist philosophy.

Continental philosophers generally reject scientism, the view that the natural sciences are the only or most accurate way of understanding phenomena. Continental philosophy stands in the Kantian tradition that knowledge, experience, and reality are bound and shaped by conditions best understood through philosophical reflection rather than exclusively empirical inquiry. This makes continental philosophy more related to the Platonic tradition of Ideas and the rationalist tradition.

Continental philosophy can be seen as a response to Immanuel Kant. The German idealism school developed out of the work of Kant in the 1780s and 1790s and culminated in Georg Wilhelm Friedrich Hegel (1770-1831 CE). Johann Gottlieb Fichte (1762-1814 CE), Friedrich Wilhelm Joseph von Schelling (1775-1854), and Hegel radicalized Kant's transcendental idealism, transforming it into an absolute idealism. Man himself became the center-point of his own existence and was made responsible for it. This individualism however did not need to lead to egoism, but to an increasing respect for the indvidual person and his life.

Friedrich Nietzsche (1844-1900 CE) and Søren Kierkegaard (1813-1855) are considered as the founders of existentialism. A central proposition of existentialism is that existence precedes essence, which means that the actual life of the individual is what constitutes what could be called his or her "essence " instead of there being a predetermined essence that defines what it is to be a human. Jean-Paul Sartre (1905-1980 CE) and Albert Camus (1913-1960 CE) would be the most popular existentialists after World-War II. The German philosopher Martin Heidegger (1889-1976 CE) with his work Sein und Zeit (1927) explored the "question of Being" in an existential and phenomenological way. In L'existentialisme est un humanisme (1946) Jean-Paul Sartre (1905-1980 CE) put forward that "Man first of all exists, encounters himself, surges up in the world - and defines himself afterwards".

Edmund Husserl (1859-1938 CE) has often been credited as the founding figure in continental philosophy. Edmund Husserl was the founder of the 20^th century philosophical school of phenomenology. Phenomenology is the study of structures of consciousness as experienced from the first-person point of view. The central structure of an experience is its intentionality, its being directed toward something, as it is an experience of or about some object. An experience is directed toward an object by virtue of its content or meaning (which represents the object) together with appropriate enabling conditions. Phenomenology provides an excellent framework for a comprehensive understanding of the natural (empirical) sciences. For a phenomenologist, inquiry is first and foremost a question of looking and discovering rather than assuming and deducing. Martin Heidegger (1889-1976 CE) explored the "question of Being" existentialy and phenomenologically and his major work was Sein und Zeit (1927). Heidegger's two most important concepts of his later thought were the difference between the Being of beings and Being as such, and the 'belonging together' of Being and man in what he eventually calls Ereignis, the 'event of appropriation'. For Heidegger modern man has relinquished his dependence upon an ultimate 'other' (God), and replaced it by a dependence on technology. Modern man now experiences himself and his surrounding world as utilities for his needs and purposes. Modern man is completely inside technology, with no glimpse of any thing or being which he cannot use technologically, such as God. Stated in another way, man freed himself out of the "sacred circle" of religion (Aristotelianism), but has created a new "technological circle" which encloses his life. Heidegger would develop a Platonic view on Aristotle and also follow the medieval separation between essence and being, which is not present as such in the work of Aristotle. Henri-Louis Bergson (1859-1941 CE) put forward the concept of multiplicity, which attempts to unify in a consistent way two contradictory features: heterogeneity and continuity. Bergson rejected what he saw as the overly mechanistic predominant view of causality and his philosophy can be seen as as a kind of process philosophy. In his Essai sur les données immédiates de la conscience deals with the problem of free will, which Bergson contends is merely a common confusion among philosophers caused by an illegitimate translation of the unextended into the extended. In his work L'Evolution créatrice (1907) (E: Creative Evolution), Bergson put forward the élan vital as the original common impulse which explains the creation of all living species.

Michel Foucault (1926-1984 CE) was a French philosopher of the structuralist and post-structuralist movement, although he himself classified his thought as a critical history of modernity rooted in Immanuel Kant. His philosophical theories revolved largely around the manner in which power controls knowledge and uses it as a form of social control to dominate the population. Foucault as a philosopher, studying the "genealogy of knowledge", was concerned with the idea of the technologization of man which accompanied the shift to a quantifiable anthropology in the French eighteenth and nineteenth centuries. In Les Mots et les choses: Une archéologie des sciences humaines (1966) he refered to the scientific épisteme, whose reformation into its modern form followed the French Revolution. Louis Pierre Althusser (1918-1990 CE) was a French Marxist philosopher. In Lénine et la philosophie (1971) and Philosophie et philosophie spontanée des savants (1967) he would put forward that Karl Marx (1818-1883 CE) had discovered a new "continent of knowledge" with his theory of dialectical materialism. The determination and clarification of a new scientific object involves an epistemological break from previous conceptions. Althusser claimed that all science involves not only knowledge of an object, but also practical intervention, by means of knowledge, in the field of this object. Philosophy existed to support the development of science and was always developed "a posteriori". It also did not have its own objects of study, but only acted upon objects of the (other) sciences. Philosophy provides the frame through and by which people look at reality. A person may not be alwayse aware of this, but the philosopher should be capable to see and understand the primary assumptions and axioms which are involved in human activity in general and scientific activity in particular. Jacques Derrida (1930-2004 CE) would respond to the phenomenology of Husserl and Heidegger. Derrida developed the critical theory known as deconstruction and his work became part of post-structuralism and postmodern philosophy. Deconstruction is a way of criticizing not only both literary and philosophical texts but also political institutions.

Analytic philosophers, mostly consider their inquiries as continuous with, or subordinate to, those of the natural sciences in the Newtonian mathematical tradition. This makes analytic philosophy more related to the logical tradition of Aristotle and the empirical tradition.

Analytic philosophy is the dominant academic philosophical movement in English-speaking countries and in the Nordic countries. The main founders of analytic philosophy were the Cambridge (UK) philosophers George Edward Moore (1873-1958 CE) and Bertrand Russell (1872-1970 CE), together with Ludwig Wittgenstein (1889-1951 CE) and (before them) Gottlob Frege (1848-1925). Frege reconceived the discipline of logic by constructing a formal system. Logic being the disciplin which can tell us if a proposition is true or not, but logic does not deal with truth in the absolute sense. In Logische Untersuchungen (1918-1923 CE) (consisting of Der Gedanke: Eine logische Untersuchung, Die Verneinung, Gedankengefüge) he discussed truth in science and the three different planes of truth from objects (Frege's First Reich), mental state (Frege's Second Reich) to a proposition in pure thought (Frege's Third Reich). Analytical philosophers reacted against the Hegelian idealism. An important milestone in analytical philosophy was the Principia Mathematica (PM) (3 Volumes: 1910, 1912 and 1913 CE) by Alfred North Whitehead (1861-1947 CE) and Bertrand Russell, which was published in three volumes between 1910 and 1913. Whitehad and Russell attempted to derive all mathematical truths from a well-defined set of axioms and inference rules in symbolic logic. The Principia stands in the logical tradition of the Organon by Aristotle and the Grundgesetze der Arithmetik by Gottlob Frege. Betrand Russell in his essay On Denoting (1905) put forward the concept of a denoting phrase and the difference between knowledge by description and knowledge by (direct) acquaintance. Frege and Russell both discovered that the condition of truth (denotation) lies in the domain of sense. In order for a proposition to be true (or false) it must have a sense; a nonsensical proposition can be neither true nor false. Robin George Collingwood (1889-1943 CE) was a British philosopher and practising archaeologist best known for his work in aesthetics and the philosophy of history. In his Essay on Metaphysics (1939) he put forward the principle of 'Absolute Presuppositions' and their Non-propositionality. At the basis of any given philosophical system there are 'Absolute Presuppositions' which cannot be proven and have to accepted. An absolute proposition is the baseline place from which the story begins. For instance 'God' is an absolute proposition, as is 'no god', as is 'all actions in the universe have causes'. From these 'Absolute Presuppositions' the rest of the philosophical system is being constructed. Although quite often the 'Absolute Presuppositions' are not explicitely stated, the critical observer should be aware of their existence and their consequences.

Ludwig Wittgenstein (1889-1951 CE) in his posthumously published epistemological work Über Gewißheit (E: On certainty) puts forward that there have to be certain things (e.g. 'Absolute Presuppositions' or 'First Principles') which must be exempt from doubt in order for human practices to be possible (i.e. 'doubt' being a practice as well). Wittgenstein also distinguishes between the concept of "knowing" and "being certain". In his posthumously published work Philosophische Untersuchungen (1953 CE) (E: Philosophical Investigations), Ludwig Wittgenstein puts forth the view that conceptual confusions surrounding language use are at the root of most philosophical problems. Language in philosophy is traditionally being reduced to representation (Augustine, Confessions, I. 8.) and this view on language is at the base of the whole of traditional philosophy. In the Philosophische Untersuchungen Wittgenstein proceeds to offer the new way of looking at language, which leads to the therapeutic non-dogmatic nature of philosophy.

Kurt F. Gödel (1906-1978 CE) with his two incompleteness theorems showed that the Principia Mathematica could not be both consistent and complete, which was a shock for the scientifc and philosophical community of the time. In his philosophical work Gödel formulated and defended mathematical Platonism, involving the view that mathematics is a descriptive science, and that the concept of mathematical truth is an objective one. Whitehead would later on become one of the fouders of process philosophy, a general theory of reality and with what exists in the world and with the terms of reference in which this reality is to be understood and explained. Process philosophy pivots on the thesis that the processual nature of existence is a fundamental fact with which any adequate metaphysic must come to terms. This contrasts with the traditional philosophical focus on things or substances, but is related to the concept of dynamis or energeia of Aristotle.

Alfred Jules Ayer (1910-1989 CE) was a philosopher of logical positivism and the Vienna Circle. His most well know works are Language, Truth, and Logic (1936) and The Problem of Knowledge (1956). In Language, Truth, and Logic he dealth with the verification principle of logical positivism, sometimes referred to as the "criterion of significance" or "criterion of meaning". It explains how the principle of verifiability may be applied to the problems of philosophy. A given statement is meaningful when it is either analytic (i.e. a tautology) or capable of being verified. Truth is only an attribute of a statement (its validity), there is no truth as an independent (eternal) entity or as a "real quality" or a "real relation". Philosophy is seen as an activity of defining and clarifying the logical relationships of empirical propositions and not an attempt to provide speculative truths about the nature of ultimate reality as in the rationalist tradition.

Alfred North Whitehead (1861-1947 CE) in Process and Reality: An Essay in Cosmology (1929) propounds a philosophy of organism, also called process philosophy. Whitehead would develop process philosophy (or ontology of becoming) which identifies metaphysical reality with change and development. In opposition to the classical model of change as purely accidental and illusory (as by Aristotle), process philosophy regards change as the cornerstone of reality-the cornerstone of the Being thought as Becoming. Process philosophy lays the groundwork for a paradigm of subjectivity, which Whitehead calls a "completed metaphysical language". Gilles Deleuze (1925-1995 CE) was a French empiricist and his most important work is Différence et Répétition (1968) in which he develops concepts of difference in itself and repetition for itself, that is, concepts of difference and repetition that are logically and metaphysically prior to any concept of identity. Difference in itself becomes a transcendental principle independent from identity. One could say that the principle of differential calculus is applied to reality. In Logique du sens (1969) he explored meaning and meaninglessness and introduced his philosophy of the event and of becoming. Later he would embrace materialism, naturalism and a vitalist constructivism.

In physics Ilya Prigogine (1917-2003 CE) distinguishes between the "physics of being" and the "physics of becoming". In his work The End of Certainty (1997) Prigogine argued for indeterminism in complex (unstable) systems as determinism loses its explanatory power in the face of irreversibility and instability. The Arrow of Time comes with the irreversibility of natural phenomena. One could also speak of the "physics of matter" (causal or a-causal) and the "physics of life" (teleological or indetermined). In 1984 he published, together with Isabelle Stengers (b. 1949), Order out of Chaos: Man's new dialogue with nature. They discuss the conceptual differences between the traditional mechanistic interpretation of the so-called laws of cause and effect and the inability of this paradigm alone to provide explanation for that class of phenomenal systems in which equilibrium conditions are not maintained. Stengers and Prigogine often draw from the work of Deleuze on questions regarding irreversibility and the universe as an open system.

Antony Garrard Newton Flew (1923-2010 CE) belonged to the analytic and evidentialist schools of thought, and he was notable (notorious) for his works on the philosophy of religion. He applied the falsification principle in Theology and Falsification to religious language, and concluded that religious statements are meaningless (scientifically). This is because there is nothing that can count against religious statements, they can be neither proved true (verified) or false (falsified). For Antony Flew religious statements are meaningless, because a religious believer will allow nothing to count against his/her beliefs. Other philosophers wanted to prove that religious language can have meaning even if it is not verified or falsified, such as Richard Swinburne (b. 1934 CE), Basil Mitchell (1917-2011 CE), and Richard Mervyn Hare (1919-2002 CE).

Ludwig Wittgenstein (1889-1951)

Modern Philosophy after Immanuel Kant
Johann Gottlieb Fichte - (1762 - 1814) "Wissenschaftslehre"
Georg Wilhelm Friedrich Hegel - (1770-1831)
Friedrich Wilhelm Joseph von Schelling - (1775-1854)
Arthur Schopenhauer - (1788-1860)
Arthur Schopenhauer - (1788-1860)
Arthur Schopenhauer - philosophy
Die Welt als Wille und Vorstellung - Schopenhauer
Søren Kierkegaard - (1813-1855)
Ernest Renan - (1823-1892)
Friedrich Nietzsche - (1844-1900)
Also sprach Zarathustra - Friedrich Nietzsche
Die fröhliche Wissenschaft - Friedrich Nietzsche
Emile Zola - (1840-1902)
J'accuse - Emile Zola
Charles S. Peirce - (1839-1914)
William James - (1842-1910)
Varieties of Religious Experience, a Study in Human Nature - William James
Gottlob Frege - (1848-1925)
Henri Bergson - (1859-1941)
John Dewey - (1859-1952)
Edmund Husserl - (1859-1938)
Nishida Kitaro - (1870-1945)
Bertrand Russell - (1872-1970)
The Problems of Philosophy - Bertrand Russell (1912)
George Edward Moore - (1873-1958)
Ayn Rand - (1905-1982)
Nelson Goodman - (1906-1998)
Simone de Beauvoir - (1908-1986)
Willard Van Orman Quine - (1908-2000)
Moritz Schlick - (1882-1936)
Rudolf Carnap - (1891-1970)
Institut Wiener Kreis - Moritz Schlick
Jean-Paul Sartre - (1905-1980)
Ludwig Wittgenstein (1889-1951)
Tractatus Logico-Philosophicus - Ludwig Wittgenstein
Hannah Arendt (1906-1975)
Jacques Derrida - (1930-2004)
Jacques Derrida - bibliography

Continental Rationalism
Stoicism
Pragmatism
Analytic philosophy
Continental philosophy

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