It is extremely important to ascertain the chronology of Platonis opera, as Plato's philosophical development is evidenced by it. In order to ascertain the relative order of Plato's writing, the following methods have been applied:

a) In order to establish the relative temporal order of the Dialogues, we can exploit all the references which were made from one Dialogue to the other. The former is, it can normally assumed safely, later than the latter. For example, Politicus made a reference to Sophistes, thus the latter is earlier, while the former is later. The same may be established between Republic and Timaeus. However, in this case, we do not take into consideration that there are many editions of the same Dialogue. Say, Apology may be rewritten several times, and through these revisions, it may be possible some additions were made although there were no essential change in Plato's philosophical thought. Therefore, we must be very careful to use this.

b) There were references made in the Dialogues to historical incidents, whose dates are known to us. Apology, Phaedo and Crito all have a reference to the Death of Socrates, so they were written after 399 B.C. And yet, there is no way of knowing the relative dates among those Dialogues. Gorgias contains a reply to a speech by Polycrates against Socrates (393/392 B.C), the Dialogue Gorgias was composed between 393 and 389, according to Copleston.

c) This method was used by Dittenberger for the first time to ascertain the relative dates of Platonis opera and it is linguistic. A certain expression Plato used a lot in earlier periods, while in his later periods its occurrence diminished such as TI MHN. The later the Dialogues get, the more often Plato use ET MHN and tt MHN. The linguistic method to examine the style was very powerful method to ascertain the chronology.

d) The testimonies of the Ancient interpreters and people like Diogenes Laërtius sometimes serves the purpose to support some chronological order.

e) The significance of Socrates in the Dialogues changes. Sometimes even Socrates does not appear at all. So we may assume that Crito is earlier, while Parmenides is later for example. The so-called Burnett-Taylor theory maintained the Socrates in Plato's dialogues are all Socratic, which is quite noble, but in actuality it is untenable.

Plato's philosophical thoughts which are transmitted to us present themselves as complex and difficult to construe as a consistent system of thought. First of all, the situation is manifold: Not only because Plato's thought evolved from the early stage through the middle one to the later attainment, but also, due to the devises he used in order to express his philosophical ideas, Plato used the form of dialogue and it is not so easy to interpret what Socrates said and what Plato thought through the mouth of Socrates. Besides, Plato=Socrates narrates a myth or a story that he once heard, which Plato used as the method to distance himself from the fact including the real Socrates. Sometimes, Plato heard from e.g. Diotima who further told a story. What we have inherited as Plato's writings are all written in the form of dialogue, which was supposed to be written for the general public and not for his students and colleagues at Academy, who were trained in mathematics and philosophy much better. It further makes it difficult to understand that Plato's thoughts have been transferred to the present day of the Western Civilization in various ways through its history.

The problem of a uniformal interpretation of Plato's philosophy has been made also more difficult not only because an apparent changes of Plato's thoughts exist, but also by the fact that Aristotle, who is almost equally great and possibly more influential than Plato, particularly during the Middle Ages due to the nature of Aristotle's philosophy based upon a similar metaphysical foundation to that of our common sense, happened to be Plato's best student. Although Aristotle made a considerable effort to distinguish his thought from Plato's by pointing out the faults of Plato's thoughts viewed from Aristotle's perspective, a great many elements of Aristotle's philosophy must have inherited from Plato's thoughts which were presented and discussed within Academy. The aspect of this problem shall be discussed in the context of Aristotle's philosophy.

Before getting into Plato's philosophy in detail, we must first examine what kind of significance Plato has in the historical perspective. What a great genius Plato may be, his philosophy cannot come into existence out of vacuum. On the contrary, Plato's predecessors were the Eleatics (Parmenides and Zeno), the Revivalists of the Natural Philosophy (e.g. Empedocles, Anaxagoras and Leucippus), and even the Miletian-Italian Immigrant philosophers (Pythagoras and Herakleitus and Xenophanes) as well as his immediate teacher, Socrates.

Plato were well versed with Pythagorean philosophy and its arithmetics as well as Euclidean geometry. Plato no doubt was well acquainted with the Heracleitian philosophy of «c cu«c 8i (Everything in flux). Without reference to his Dialogue titled Parmenides, Plato was confronted by Parmenides with the Eleatic Philosophy to comprehend reality. Probably, Empedocles and Leucippus are common-sense knowledge to Plato, too. Socrates=Plato extensively discussed Anaxagoras in Phaedo and said that when Socrates was young, he studied Anaxagoras' philosophy extensively. No doubt, Plato must have studied Anaxagoras, too, otherwise he could not have written that portion of Phaedo as good as it is.

Without the specific reference to such dialogues as Protagoras, Gorgias and the Book I of Republic (which was supposed to be originally called Thrasymachus), Hippias and The Sophist, we are made aware of how much Plato knew about the sophists and their activities (and also how much energy Plato poured to criticize the Sophistic approaches).

In the above mentioned, though Plato's understanding of his predecessors' thoughts were not quite so systematic, all those converged and provided Plato and his philosophy with indispensable elements for a further development of the history of philosophy. Of course, some of them may be positively, the other, negatively, and yet this was historically the first event in which a philosopher not only inherited the questions of the past philosophy, but also accepted so many influences and made them integrated into one's philosophical ideas.

How was this pursuit of wisdom accomplished?

Following Socrates, Plato attempted to search for reality as it really was in that which becomes the predicate and not the subject of a proposition (that is exactly the opposite to Aristotle's search for substance). According to Plato, the early Socrates in the Platonic dialogues, i.e., the real Socrates himself, searched for the essence or the genuine being (ousia) of that which becomes the predicate and not the subject of a proposition. He asks the question in the form of "cH lacHl?" (What is it?) When Socrates tells his opponent, "I am asking you to answer and show me, not this courageous act of Heracles, or that courageous deed of Antigone, but courage itself or the essence of courage, the real courage by which a particular action is courageous." There are millions of beautiful things, such as a beautiful bird, a beautiful house, a beautiful young woman, a beautiful briefcase, etc., but they are mutable and not universally valid due to the origin of their knowledge (sense experience, aisthesis). Thus they provides us no genuine knowledge of say, the beauty itself. According to Plato, there must be something (which may be called "cause" or "principle.") which is shared by those things and yet something absolutely beautiful itself which neither diminishes nor increases and is in itself unchanging and everlasting as well as universally being so.

This assumption became already a firm conviction in the mind of Socrates, although Socrates apparently did not find the answer to his own question and left it to Plato to solve. Socrates' significance is that he was so close to the answer itself, but did not know how to describe it as the genuine reality. Nor Socrates would not establish such a metaphysical beings and their system called the world of Idea.

What Plato, together with Socrates, looked for was the Beauty itself, the essence of Beauty which is one, while beautiful thins are many. In stead of the concrete, particular things, which become the subject of a proposition, Plato searched the Universal, or the essence of reality in itself which can be predicated of those concrete, particular things which are its subjects. Indeed, a particular, individual person becomes beautiful and later perhaps becomes no longer beautiful. Thus, the predicate of this person is ugly in stead of being beautiful.

However, in this search for the Universal or the Ideal Essence by Plato, it became more and more obvious that these Ideals and Forms are not only those of "things" (which would create more problems to the later Plato, e.g. the Idea of nail, the Idea of hair, the Idea of mud, etc. cf. Parmenides), but they are rather Values themselves as Ideals. We do not have to point out such examples as those Plato uses in his dialogues: e.g., Good in itself, Beauty in itself, Justice in itself and Courage in itself.

Even the essence, "wisdom," was viewed more often as a Value or an Ideal rather than an actual, concretely possessed knowledge. Therefore, in Plato's thought at the middle period, there is an unbridgeable cleft between the Wisdom as a Value or an absolute Ideal and the actual wisdom which seemed to be possessed by Pericles or other politicians or philosophers, for example. The essence of value is unattainable or non-graspable unless he/she "dies" and is completely freed from the body and sensuous desires (in Apology, Phaedo and Symposium). Besides this essence of a value cannot be given as a form, as Aristotle contended. On the contrary, neither is it possible to intellectually grasp the form of a thing, but to Plato, an essence of thing as a value (e.g. Beauty itself) is to be recognized by supersensory, intellectual intuition (nohsis), not by such a logical procedure as a dialectic in itself. Indeed, dialectic is an essential portion of discovery and revelation of an essence as a value in order to take a correct steps to the point. At this point itself, the dialectic must be silent and the nohsis (intellectual intuition) must take over its task of revelation of truth.

Furthermore, today in particular ,we still naively have no doubt about the all-mightiness and unlimited validity of natural scientific explanations and about the so-called Contemporary scientific value-free approach as the sole means to comprehend being. Therefore, we often forget Plato's great uniqueness in and profound contribution to the insight into his ontology based upon Value rather than the mere "thingness" of being in the history of Western philosophy. Aristotle never understood this accomplishment of Socrates and Plato.

The concrete, particular thing changes, and nothing of this kind remains the same. In this sense, Plato inherited Heracleitus' insight into the reality such that Plato saw that everything in the sense world is in constant change.

On the other hand, Plato could not help but notice that this Beauty itself which is not only immutable and eternal in distinction from those concrete, particular beautiful people or things must exist. Plato calls Justice Itself, Good Itself, and Beauty Itself as Ideas or Forms. Probably the early Plato who was exposed to Pythagorean philosophy and saw in it an excellent model of, and a parallel to, this in mathematics. The number three may be represented by three apples, three books, or three persons, but the number three itself is quite different from those particular, concrete objects and retains its identity and constancy. (Aristotle on the contrary, held that the number is an abstraction from concrete, particular individual things.) To Plato, however, this number is not abstracted from those three things, but those three things are three by virtue of the number three. In this sense, Pythagoreanism exercised a great influence on Plato's thought (Incidentally, the number is known to us through understanding clcumlc and is considered otologically as an intermediary between the Ideas and the concrete, particulars, although the number is far more close to the Ideas in fact. See Book VII of Republic). Furthermore, Plato follows Parmenides' path of Rationalism in that, not the senses, but Reason alone, can grasp this Beauty Itself, Justice Itself and Good Itself. Once again after Parmenides, Plato calls this world of Ideas the genuine reality in distinction from the world of appearance which is a mere illusion. Since in the phenomenal world, everything is in constant change, so argues Plato following Heracleitus, there cannot be knowledge. For any object in the world of appearance, being the mixture of being and non-being, change is inevitable. Therefore, Plato calls our information about the phenomenal world opinions, while he reserved the name of knowledge only for the Ideas, because the Idea alone is unchanging, eternal, thus real in the genuine sense.

In a sense, Plato exerted himself most intensively to argue against the sophists and their philosophical ideas. In order to justify the love of wisdom (= i OlmÁmOlc), the search for knowledge and values, as long as it is meaningful, the object of the search and its knowledge cannot be relative, nor subjective. If it were relative, every person has to become indeed the "measure of all things." What is perceived by each is true and value to each. Thus, first of all, we are not able to explain or understand the phenomenon of being false. Secondly, there is no universal truth, there is no absolute truth different from each individual's opinion. According to the sophists, truth is reducible to an opinion of each individual. This threatens the very foundation of philosophy itself, i.e., the learning and the search for knowledge as such.What was the most challenging task to Plato was to positively (unlike Socrates who negatively tried to demonstrate that knowledge cannot be opinions) justify the absolute objectivity of truth and knowledge so that all the serious philosophers' endeavor is not meaningless, but significant. In this sense, Plato owes a great deal to the sophists, however negative sense it may be. In order to accomplish this task, Plato had to "postulate" the world of Ideas or Forms as the genuine reality.

When knowledge was threatened by the sophistic argument and their relativism, Plato had to stand up, defend and philosophically justify the objectivity (universal validity and necessity) of knowledge and values by means of the reality of the immutable, eternal Ideas. Here knowledge and values were indeed no longer unquestionable, but rather highly questionable to the contemporary of Plato.

Plato's defense for the objectivity of knowledge was attempted by establishing an ontology which meets the Parmenidian criteria for truth of the identity of knowing and being. In order to do so, the reality cannot be searched among the phenomenal world, but must be searched beyond the world of appearance. What is discovered was no other than the world of Ideas. While René Descartes attempted to demonstrate the apodeictic knowledge of oneself to secure a new vista of knowledge, Plato exerts himself to reveal for truth and genuine knowledge the existence of the world of Ideas and Ideals, without which no objective truth is considered as possible at all.

By the following way, we may be able to answer to the question of "What kind of place has Plato and his philosophy occupy in the history of Western philosophy and its civilization?"

Namely, Plato stood in the face of the sophistic relativism, skepticism and even nihilism of truth and knowledge as well as morality and values. It was the crisis of philosophy and culture. This new trends threatened the society, the religion, the politics, the morality and the pursuit of knowledge from their foundation. Plato was to overcome this nihilism, skepticism and relativism so that our speech, our utterance, our judgment are not mere murmurs, but are meaningful and either true or false. When we say that justice is virtue, while injustice is vice, this utterances are indeed meaningful and the distinction is actual. The genuine distinction between a truth and an opinion must be drown so that it is not non-sense to say that I know that I do not know.

This task of overcoming the sophistry was further succeeded by Aristotle, but in a different way, which we are not going to discuss here.

Metaphysics or Ontology: The Doctrine of Forms

Plato's starting point was Socrates' question: cH lacHl? (What is it?) In the agora (market place) of Athens, Socrates asked his cross-examined to try to have him see courage as such rather than a concrete, particular courageous act or a concrete, particular courageous person. In stead of the socalled denotational definition, Socrates demanded a connotation definition of courage itself. As far as we can see, the so-called early Dialogues, neither Socrates, nor his cross-examined, were able to give the answer to Socrates' question in and quest for the essence of things as a form of connotation definition. It may be probably why Socrates kept saying, too, that he was aware that he did not possess wisdom or knowledge. Plato perhaps asked himself how truth, knowledge, values and morality are possible as something objective and real, not merely subjective and relative. This was indeed an epistemological question (as the case of Immanuel Kant), but this condition for the possibility of our knowledge and values was not provided by Plato as the groundwork of epistemology within itself, but exclusively as metaphysics or ontology. As mentioned above, the meaningfulness of the pursuit of knowledge (=love of wisdom lmÁmOlc) is only possible when knowledge is neither subjective, nor relative. Plato was well aware that he could not seek the knowledge in the world of appearance, as this world of appearance known to us by senses is the mixture of being and non-being, thus it is in constant flux. Nothing in the phenomenal world is abiding and immutable, so if our "knowledge" is limited to the object of this world of appearance, there would possibly be no knowledge in the strict, objective sense. Should it also mutable itself or in its object, it is not worth the name of knowledge at all. (Yesterday's truth may be today's falsehood.) Plato readily accepted the world of appearance as fluid and in constant change, for not only it was a matter of actual experience, but also there was a strong influence from Heracleitus.

Instead of the way of knowing (as the case of Descartes and Kant, for example, in the Contemporary periods), Plato's search was directed to the way of being as reality, which is to be different from the mutability and transiency of the being of the world of appearance. Knowledge and values are to be "anchored" on the immutable, incorruptible, unchanging being, so that knowledge (and values) are knowledge (and value) of reality, namely the knowledge with its objectivity (i.e., the universal validity and necessity). It is indeed self-contradictory to say that knowledge is not the knowledge of reality.

On the one hand, following the tradition of the Eleatic philosophy (Parmenides, Zeno and Melissus), Plato held the "knowledge" of the world of appearance to be mere cm c (opinion) and sought knowledge and values in the realm of real beings («m mu«s muE beyond our senses. This genuine reality («m mu«s mu) is to secure the objectivity of knowledge, thus knowledge itself.
On the other hand, in response to the challenges from Parmenides and his followers who held the genuine reality to be the Being, the Atomists (Leucippus and Democritus) sought the genuine reality in the ultimately indivisible matter called «m c«mOmu (atom) which is also unknowable by our senses.

Being well aware of those Revivalists' approach (Empedocles, Anaxagoras and Leucippus and Democritus), Plato rejected such materialism (the ontology which attempts to explain the reality (all the things) by, thus reduce it to, matter) as the Atomists' theory. Instead Plato tried to see the genuine reality in that which is to be grasped by the definition of a predicate term, namely what Socrates beheld as the object of the ultimate definition, i.e., as the answer to his question of "TI EaTIN." This object of the ultimate definition was called Idea (IDEA) or Form (lHmda).

As stated before, according to Plato, the world of appearance is, just like the world of Heracleitus, in perpetual flux, and due to this essential character, everything in the world of appearance is a mixture of being and non-being, fails to constitute the genuine reality and cannot offer the basis for the universal, necessary knowledge. Of the object of the world of appearance, it is called opinion instead of knowledge. What we opines is, for example, a beautiful woman, and not beauty as such. Anything that we perceive by our senses, thus, always possesses at least a character (e.g., courageous) for which we have the name (courage cuc8lmÁ). Since an entity in the world of appearance is in itself incessant changing, the essence or nature of this object (in regard to its attribute or character) cannot be found in this change or nor in non-being, on the contrary, it must be sought in its true essence, its true being. This is the reality according to Plato. It is goodness as such rather than some particular thing being good or a concrete act which may be called good. Not a just judgement, but justice itself is a true being and it is called by Plato a Form or Idea. These Forms or Ideas which are nothing but the essences of things both in thingness and value, for which we possess names. Therefore, what are referred to by names, that which are stated primarily by predicate terms rather than by subject terms of a proposition (that which correspond to the true answer to the Socratic question of cH lacHl) constitute the genuine reality, the true being.

In Republic, for example, it is assumed that whenever a plurality of individuals have a common name (which refers to a common characteristic), they have also a corresponding idea or form. This is the universal, the common nature or quality which is grasped in the concept, e.g. beauty itself, as we saw above. Namely there are many beautiful things, while we form one universal concept of beauty itself Plato considered that this universal beauty for instance is not a mere meaning, nor a subjective concept, but an objective universal essence of beauty as genuinely real being. What is the essential characteristic (e.g. beauty) of a particular, concrete thing in the world of appearance is beauty itself «m ecmu c «m e¢c «m, while that concrete, particular beautiful thing are called by Plato in Republic its shadows. They are shadows because otologically they are mixtures of being and non-being, and because epistemologically they are not objects of our reason for genuine knowledge. By virtue of participation in this beauty itself, the beautiful things in the world of appearance become and are beautiful.

Without such an objective essence of beauty in itself, there is no way in which we are able to have the genuine knowledge of universal beauty as such, in consequence, the beautiful things either.

Since this beauty as the Ideal Value (Being at the same time) cannot be known through senses by which we perceive and "know" beautiful things, how is it possible for us to have the knowledge of those Ideas? Plato contended that there is no way we learn or acquire the knowledge of e.g. this universal essence of beauty. Ideas such as an essence of beauty must be known or grasped only through the intuitive grasp of reason. However, as long as we are imprisoned in our body and using our senses, we can only seek and love the knowledge of Ideas and will never be able to possess the wisdom. Because it cannot be acquired, the prima facie learning or acquiring of such an essence is according to Plato nothing else than cucOuiÁlÁ (recollection) of what we had known before in previous lives and had forgotten. In order to guarantee this a priori knowledge of such an essence, Plato argues in Phaedo that we must have reborn or that we had lived many lives previously in which we already possessed the knowledge. This is Plato's famous theory of recollection cucOuiÁlÁ together with the doctrine of reincarnation.

Together with these ontological doctrines associated with the theory of Forms, Plato apparently inherited the doctrine from the Pythagoreans that our body is the prison for our soul, while philosophy is the preparation for the purification of our soul from its being mixed with the body (while the Pythagoreans further held that the purification of the soul through mousiké will break the chain of karma).

Now question is concerned about the world of Ideas or Forms as the genuine reality and how it is related to the world of appearance:

l) Plato clearly not only presupposes, but is firmly convinced that there is an ontological sphere of Ideas completely apart from and independent of the world of appearance. However, these Ideas are Ideals, perfect Values and criteria of reality and truth for the world of appearance known to us by the perception.

2) Aristotle asserted and criticized that Plato alienated and separated the world of Ideas from the world of appearance.

3) In Timaeus, Plato stated, though it was a myth, that the Creator or the Demiourgos made things of this phenomenal world according to the model of the Forms. This implies that the forms or Ideas exist apart, not only from the sensible things that were modelled after the Ideas, but also from Creator, who takes the Forms as His model. The r8c or mcmril the receptical, was already conceived here which will be molded into matter in Aristotle's philosophy.

4) In Phaedo, Plato maintains that we shall never obtain the knowledge of Ideas as long as we are imprisoned in the body and disturbed by our senses.

5) In Symposium, Socrates had been supposed to have a discourse with Diotima, a Prophetess, concerning the soul' s ascent to true Beauty «m mu«Á ecmu under the impulse of Eros m 8Á. 'd 8Á or Love is stipulated as the means or inbetween between Plenty m8mÁ and Poverty i8lcI Love is itself neither good nor bad, neither beautiful nor ugly, but it lacks beauty and wisdom and yet it knows that it lacks them and is in pursuit of them. Thus, the eros or Love is used in order to construe philo-sophia.

However, it is important to note that in Symposium Plato talks about desires in general l« Olc, philosophy, love of wisdom OlmÁmOlcl is nothing to do with sensory epitymia (desire), but Eros in philosophy is placed in a higher plateau.

6) In Republic it is clearly shown that the true philosopher seeks to know the essential nature of each things. He is not concerned to "know," for example, a multiplicity of beautiful things or a multiplicity of good things, but rather to discern the essence of beauty and the essence of goodness, which are embodied in varying degrees in concrete, particular beautiful things, and concrete particular good things in the phenomenal world. Non-philosophers, who are almost completely occupied with the multiplicity of appearances with sensory pleasures so that they do not attend to the essential nature and cannot distinguish, e.g. the essence of beauty from the many beautiful phenomena. Non-philosophers only have the opinion cm c and could not even glimpse into scientific knowledge.

7) In the Phaedrus Plato speaks of the soul who beholds "real existence, colorless, formless and intangible in sensory perception, and knowable only to the intelligence" i cr8Oc«mÁ « ecl cÁriOc«lmÁ ¨c«l umm), and which sees distinctly "absolute justice, and absolute temperance, and absolute knowledge itself ...which exist as real and essential being" («iu u « m Á«lu mu mu«Á lÁ«iOu m Ácu).

8) At the beginning of Parmenides, on of Plato's later dialogues, the question is raised by the godlike 70 year old Parmenides with white beard: What Ideas is the young 19 year old Socrates prepared to admit? In reply to Parmenides, Socrates admits that there are Ideas of "likeness, and of the one and many," and also of "the just and the beautiful and the good," etc. In answer to a further question, Socrates says that he is often undecided, whether he should or should not include Ideas of man, fur, water, etc. While, in answer to the question whether he admits Ideas of hair, mud, dirt, etc., Socrates' answer was "Certainly not."

9) In Sophist, also one of the later dialogues, the object before the interlocutors is to define the Sophist. They are aware of a notion, what the Sophist is, but they wish to define the Sophist's essence in a clear mtmÁ (words) to capture the Sophist.

In Theaetetus, another later dialogue, Socrates rejected the suggestion that knowledge is a true opinion ci¨i cm c or an opinion with an "account" mtmÁ While in this dialogue, discussions were concerned about particular sensible objects, in Sophist, discussions turn to class-concepts. The answer apparently given to the problem of the Theaetetus is that knowledge consists in apprehending the class-concept by means of genus and difference, i.e., by definition.

10) In Sophist, Plato clearly indicates that the whole complex of Forms, the hierarchy of genera and species, are "comprised" in an all-permeating Form, the Idea of Being (It was the Good «m ctc¨mu in Republic, and he certainly believes that in tracing the structure of the hierarchy of Forms by means of analytical understanding clcl8iÁlÁ, he was detecting, not merely the logical structure of Forms, but also the structure of ontological Forms which are the Real. But whether successful or not in Plato's division of the genera and species, was it of any help for him to overcome i r8lÁOmÁ (the separation), the separation between the particulars and the infinite species? In the Sophist, Plato showed how divisions are to be continued until the c«mOmu lcmÁ (the no longer divisible form) is reached.In the apprehension of those «c c«mOc lcl (the no longer divisible forms), cm c (opinion) and i clÁ¨iÁlÁ (sense-perception) are involved, though it is themtmÁ alone that determines the "undetermined" plurality. Philebus assumes the same, namely we must be able to bring the division to an end by setting a limit to the unlimited and comprehending sense-particulars in the lowest class, so far as they can be comprehended. For Plato, the sense-particulars as such are the unlimited and the undetermined! They are limited and determined only in so far they are classified among the c«mOc lcl (the no longer divisible forms) and it is not possible to be subsume under them, if they were true objects at all. In other words, they ar not fully real. In pursuing the ccl8iÁlÁ as far as the atomon eidos Plato was able to comprehend all Reality. Therefore, Plato said,

Despite the fact that Plato may have considered to have solved the problem of the r8lÁOmÁ (separation), it remained to bee shown how the concrete, particular things in the world of appearance come into existence at all. It may well be acceptable that the whole hierarchy of Forms with its complex structure comprised in the all-embracing One, the Idea of Being or that of the Good which is the ultimate and self-explanatory principle, the Real and the Absolute. It should nevertheless be necessary to demonstrate what makes the world of appearance be as it is, although this world of appearance, being not fully being, is not simply non-being either. In Timaeus, one of Plato's later dialogues, Plato's attempt to answer this question is revealed. There, Plato carefully told us as a myth, the Demiourgos miOlm 8tms is describing as conferring geometrical shapes upon the primary qualities within the mcmri (Receptacle) or r8c (Place), and so introducing the order into disorder, taking the "intelligible realm" of Forms as his model or ideal in creating the universe. However, it is often pointed out that the work of the Demiurge, the creation of the world of appearance, should be considered rather as an analysis, by which it would articulate the structure of the material world from the work of the rational cause, i.e., would distinguish the 'primary' chaos from the world of Ideas as the Cause. This however does not necessarily imply that the chaos was ever actual. Thus the chaos is primordial in the logical sense. If so, we must conclude, the mcmri or non-intelligible part (=Aristotle's matter) of the world of appearance is merely assumed and not explained.

11) Plato's theory of Forms in itself was a great accomplishment in comparison to the Pre-Socratic and Sophistic philosophies. Needless to say, influences from Parmenides, Pythagoras to Herakleitus (and even some of Sophists' conceptions about our sensible world and logical investigations) were obvious in Plato's developing his Idealism.

Plato's theory of knowledge was developed with the profound conviction that knowledge is, neither subjective, nor relative, but primarily objective, i.e., related to reality which is being, therefore, knowledge is universally valid and necessary, as Socrates was convinced. Facing the challenges of the sophists, who do not recognize the objective knowledge, but assert that knowledge is no more than a mere opinion and that the truth is the truth of the beholder (ref. Protagoras' "The human is the measure of all things..." and Gorgias' "Nothing exists. If anything exists, it cannot be knowable. Even if it is knowable, it is uncommunicable.").

Plato not only believed in, but also must demonstrate the meaningfulness of the Socratic mission to pursue knowledge and wisdom, but also to urge other to do so. For the general understanding of the intellectuals of his time was that the sophists' contention be right and that the only knowledge we may pursue be the art of persuasion (hé rhétoriké). Therefore, the truth, according to the sophists, is demonstrated by winning an argument and depends upon if one is capable of induce others to also accept the contention, and there is no such a thing as an objective truth nor ignorance. For everybody is equally wise! Plato's endeavor was his attempt to redeem Socrates and his Mission by demonstrating that the sophists were radically wrong and that there must be the objective truth and wisdom.

As stated above, Plato's epistemology is grounded on the basis of his ontology. In other words, it is determined by and parallel to his ontological structure he envisioned (cf. Republic, Book VII).

According to Plato, what we call "knowledge" in our common sense may be divided into two groups in accordance with the four different object domains of information. Those four domains of "objects" or "entities" are hierarchical in terms of "reality" such that 1) lemuis (semblances or mere images) ‹a portrait or a sculpture or an image mirroring on the serene surface of water‹ is the lowest, then 2) cm c (opinion or "information" about sensible objects) for the second, 3) Oc¨iOc«lec (numbers and geometrical figures) for the third, 4) umi«c (Ideas or Forms) for the highest.

In parallel to these distinctions, our cognitive faculty is divided into four faculties:
1) lecÁlc (likening), 2) lÁ«ls (belief), 3) clc8iÁlÁ (understanding), 4) umiÁls (Reason), and the ascendance of value is in this order. Since Plato allows the name of reality only to mathématika and noéta, while doxa are considered as copies of the reality (a beautiful flower in distinction from beauty itself, for example) and eikones or images are copies of copies, the name of knowledge is strictly reserved by Plato for umiÁls (Reason). In the domains of Eikones and Doxa, illusions, errors and falsities are possible, while Oc¨iOc«lec and umi«c do not allow any falsehood, an error or an illusion. They are a priori knowledge.

Then, how the Noeta and the Mathématika differs? According to Plato, Noéta are known by dialectics which do not make any assumption or premiss, but goes back, step by step, to the most basic principle, while Mathématika are known, though a priori and necessary, on the basis of the premisses, assumptions (axioms). Philosophy, therefore, are presuppositionless!

According to Plato, i clce«lei «rui (dialectics) is the method of philosophical inquiry that alone can reach the genuine reality, namely Ideas of Forms such as Beauty itself, Good itself, and Justice itself, etc. Between two independent minds (or so imagined at least even within one mind), a discourse or clcmtms takes place such that the one proposes an understanding of something (e.g. justice) by word (mtmÁ), then the other critically examines this and proposes another solution to substitute by eliminating the fault of the first one. This process will be repeated many times until they come to grasp the object of their understanding itself. However, as Socrates portrayed in Plato's early dialogues, it is not only not easy, but also not possible for an object of inquiry to be grasped by logos particularly when the object is more fundamental (such as being «m mu, good «m ctc¨mu). Plato believes that in such a case, we must intellectually intuit (umlu) the Form or Idea at last. It is a matter of controversy whether or not this intuition be included in dialectics. However, we take such a stand that since dialectics deals with the object solely by words in the double sense (dia-legein and using logos to grasp the object), this intuition, the immediate grasp of the object by noésis is distinct and separate from the process of dialectics. They constitute, however, a whole in the sense that both of them are functions of reason.

lÁ¨iOi
(knowledge)
umiÁls umi«c
(reason) (Ideas or Forms)

clcumlc Oc¨iOc«lec
(understanding) (numbers)

lÁ«ls ` cm c
(belief) (opinion)

lecÁlc lemuis
(liken) (semblance)

As Heracleitus maintained that everything is in constant change, Plato, too, held that the sensible world, i.e., the world of appearance (which we normally consider to be the reality) is in constant flux. Thus the ontological status of the sensible things (the things in the phenomenal world) was, according to Plato, not being, but it is becoming, i.e., the mixtures of being and non-being. Or sometimes Plato called it the shadow of reality, i.e., the shadow of true being, as he tried to illustrate the sensible things by means of the Allegory of Cave in Book VII of the Republic. Since sense perception is exclusively related to the sensible thing which lacks the true being, but something like a being, our senses cannot provide us with knowledge at all, but what we have through senses is mere images (eikones) or doxa (opinion).

Therefore, ignorance, according to Plato, is related to non-being, while knowledge is related to the true being, the reality, which must be not only unchanging, but also does not allow any error. Thus what we normally consider as being real, the object of our sense perception, cannot be so. Plato names the information of the sensible thing through our perception primarily a doxa or an opinion. Needless to say, this opinion cannot be called knowledge in the true sense because its object is not a being, but a mere shadow or a mixture of being and non-being. Of the sensible thing, can we learn and obtain a true opinion, and yet the object of doxa is a sensible thing, and we may also make a mistake. So we cannot call a true opinion knowledge at all.

The true being, being the object of knowledge, however, is independent of our sense experience and can only be known by reason um Ál so knowledge, then, is something which can not be 'learned' by empirical generalization nor can be acquired through common sense. On the contrary, due to its immutability and absolute nature, it must be 'remembered' by us. This is called Plato's recollection theory.

The object of our knowledge is called an Idea or Form, by means of which the sensible thing can exist and be named, so through the Idea or Form alone, we are able to recognize the sensible things. What we experience through our sense perception is, for example, Isabella, a beautiful young woman and not beauty itself. She is indeed beautiful because she participates in the beauty itself and as long as she does so, she is and remains beautiful. And Isabella is called "beautiful." However, as time goes on, she becomes older and no longer beautiful, as she no longer participates in the Idea of beauty «m ecmu. If we think that we recognize the beauty which she has in her is the beauty itself «m ecmu c «m e¢c «m, then we are making a mistake, for she will sometime become no longer beautiful and will turn into ugliness (if not, at least not beauty). Such a mutable thing as a young woman and its quality possessed by her cannot be the object of our knowledge. Something mutable is not a real being, but a kind of mixture of being and nonbeing (by virtue of which change is possible). The object of our knowledge is the true being «m mu«Á mu which is something immutable and is in itself (unlike a beautiful thing that is not being in itself, but a being in other), that is, the beauty as such «m ecmu c «m e¢c «m, the goodness as such «m ctc¨mu c «m e¢c «m, the honesty as such «m ci¨ «lemu c «m e¢c «m, etc. In other words, it is the Form, and there are as many Forms as are positively valued such as beauty, courage, grace. gentleness, harmony, and happiness. The Ideas are not only those values, but also essences of things such as being human, being a house, being a polis, etc. However, these essences of things are to be Ideals of those things, so to know those Ideals means to know the criteria for those things at the same time. That is why Plato was able to talk about the Ideal city state in distinction to other actual city states in terms of its political form. Thus, Plato maintains that knowledge can be knowledge of Ideas, and nothing else.The question of the theory of Ideas was extensively discussed in the section of Metaphysics and it is probably not necessary to repeat it here.

Plato's theory of Knowledge may be well disclosed in a negative way in Theaetetus, one of his later dialogues, in which Plato attempted to show that what is generally considered as knowledge, such as a perception, an opinion and a true judgement, cannot be knowledge at all, as long as "knowledge" is considered to be related to the object of the phenomenal world. However, in Theaetetus, Plato did not show positively what knowledge as such is and yet he demonstrates there that the theory of knowledge is meaningless, unless falsity can be accounted for. In Protagoras' theory of the human being to be the measure of all thing, falsity can have no place at all.

As we saw above, it is better discussed in Phaedo and Republic.