Late Plato's Idea Theory Research

The foundation of Plato’s philosophy and its’ core thought are the theory of idea（or form）, itsmetaphysics, epistemology, dialectics, theory of ethics and politics, poetics, the doctrine ofcosmos creation are closely related to it. However, Plato’s the theory of idea is not immutable andfrozen, it also has its process of origin, formation, development and improvement. The researchobject of this dissertation is Plato’s late theory of idea.This dissertation researches emphatically Plato’s late theory of idea, comparing it with hisprevious one, on the basis of this, to understand the evolution of Plato’s theory of idea. Theresearch focuses on Parmenides, Sophist, Theaetetus and Timaeus, the referred themes are asfollowing: the reflection and critique of the early theory of idea and the meaning of eighthypothetical reasoning in Parmenides; the combination of the five greatest ideas(kinds),developing the dialectic of philosophical ideas and the initial shape concerning the series ofphilosophical categories in Sophist; the three definitions of knowledge in Theaetetus; the latetheory of idea embodied in the doctrine of universe creation in Timaeus. Through the analysis ofkey issues, the dissertation strives to clarify the relationship of inheritance and change between theearly and late theory of idea, to explain the connection of late theory of idea with dialectic,theoryof philosophical category,epistemology and the doctrine of cosmology.The first chapter outlines Plato’s time background, ideological background, life, his maindialogues and evolutional clue of his idea theory. The second chapter mainly discusses the“universal definition” of Socrates and Plato’s early theory of idea, demonstrates that the latter isinherited and developed from the former, and compares the similarities and differences of both.The third chapter mainly analyzes the important dialogue Parmenides, which initiates the latetheory of idea. It begins to reflect on the early theory of idea, reveals the potential conflictsbetween the nature of idea and the “participation”(or “share”) relationship, exposes the“separation” problem, and tries to explain how to solve the difficulty of “separation” and“participation”, i.e., to demonstrate that the opposite ideas can be combined, so as to eradiate thesevere separation of idea. The fourth chapter discusses the late dialogue Sophist, whose corecontent is the theory of communicating greatest (i.e., the most universal) kinds, which marksimportant evolutional phase of Plato’s thought. It deepens the view of combination of oppositeideas put forward initially in Parmenides, on this basis, further proposes that not only suchopposite ideas as “Being” and “Non-Being” can be combined, but also, to a great extent, the threepair of opposite categories (“Being” and “Non-being”,“the Same” and “the Different”,“the Rest”and “the Change”) can be combined with each other, especially that some of the basically greatestkinds (namely philosophical ideas) can penetrate all the other ideas and particular things. It thusdevelops the theory of idea combination and the doctrine on category of philosophical ideas withcertain universality, seeking to resolve and overcome the problem concerning separation of thetwo worlds. The fifth chapter discusses Plato’s late important dialogue Theaetetus concerning thedefinition of knowledge, which tries to solve the separation problem in the epistemology. This dialogue indicates that such human beings’ cognitive abilities as “perception”、“judgment”、“reason” have a certain relevance, therefore, the problem of separation between “knowledge” and“perception”,“opinion” can be eased to some extent, they are no longer entirely separated in termsof epistemology, but can communicate with each other, that is characteristic of the late Plato’s“theory of knowledge”. The sixth chapter discusses Plato’s late dialogue Timaeus, in which Platoestablishes his doctrine of universe creation, and it is the only Plato’s dialogue of naturalphilosophy. In this dialogue,“the soul of universe”(the whole of ideas),“space”(receiver),“time”and “Necessity” are all closely related to the theory of idea, they can play some role of“combination” for the two worlds of “idea” and particular things; Timaeus provides the newmeasures to solve the problem of “separation”, and also suggests that there still is intercommunitybetween the early theory of idea and the late one.Plato’s late theory of idea has profound and lasting influence on future generation of westernphilosophy, the formation and development of ancient Greek and Roman philosophy (includingthe philosophy of Aristotle and the Hellenistic and Roman philosophy) and Christianphilosophy-theology are all built on the basis of their absorption of and inheritance from orcriticism to it, the evolution of western philosophy, culture and civilization can all manifest themajor effect of the late Plato’s idea theory.