(The transliteration "Idea" is misleading, owing to the psycholo gizing of the sense of the word by Locke and his followers.) The sensible things of which we predicate beauty, goodness, humanity, have only a secondary and derivative reality. Strictly speaking, we must not say that they are this or that, but only that they become this or that for a time, in virtue of the temporary "pres ence" (rapovcria) to them of the corresponding Form, or, as it is also expressed, in virtue of their "participation" (00etts) in the Form. A sensible thing, in fact, is simply a temporary complex of Forms.
In the Parmenides of Plato Socrates is made to expound this doctrine to the great philosophers Parmenides and Zeno as his solution of the standing puzzle of the one and the many. This is the doctrine of Forms (the "Ideal Theory") as it is stated in the Phaedo and Republic. Though it is quite different from the version of the doctrine ascribed by Aristotle to Plato, it has been usual in the 19th century to assume that it is an earlier form of that doctrine consciously devised by Plato after the death of Socrates.
The chief argument for this view is based upon the observation of Aristotle that Socrates rightly "did not separate" the universal from the particular (Met. M., 1078 b3o) as, it is apparently im plied, Plato did. It is, however, not clear that Aristotle means by this, what he never says expressly, that Socrates did not teach the doctrine ascribed to him in the Phaedo. He might equally mean that the doctrine of the Phaedo does not itself involve the kind of "separation" of the universal from the particular to which he objects in what he describes as the Platonic theory, and, since the Phaedo is one of the Platonic dialogues to which he most fre quently alludes, it is strange that he should never have said that it misrepresents the historical Socrates on a capital point, if he really thought so.
On the other side, the doctrine is expressly said in the Phaedo to be a familiar one which Socrates "was always" repeating, and it is hard to believe that Plato could have made such a statement about a speculation of his own, especially as most of the person ages of the Phaedo were certainly still alive long after the dialogue was written. It is hard to see what could be the point of such a mystification, and harder to understand how its author could have expected it to be successful. Of course, demonstration is out of the question in such a matter; we can only be guided by con siderations of probability. If we think the probabilities against the view which credits Plato with deliberate mystification, we must be prepared to admit the possibility that he is also reproducing the thought of Socrates in the further development of the Sym posium and Republic, where we hear of a supreme Form, that of Beauty, or Good, the vision of which is the far-off goal of all in tellectual contemplation. We may fairly suspect that the thought of Socrates is undergoing development in the mind of Plato, but it will be natural to regard the development as, in the main, un conscious, and to recognize that no complete separation of the Socratic and the Platonic in the result is possible.
It is certain that on the logical side the thought of Socrates proceeded "as if" the doctrine of Forms expounded in the Phaedo were its point of departure. Both Plato and Xenophon bear out the remark of Aristotle that Socrates may fairly be credited with two things, "inductive arguments" and "universal definitions" (Met. M., 1078 b27). The "universal definition" is an attempt to formulate precisely the meaning of a universal significant predicate, i.e., to apprehend what the Phaedo calls a Form, and it is from the practice of Socrates, who aimed at the clarifica tion of thought about the meaning of moral predicates as the first indispensable step to the improvement of practice, that the theory of logical division and definition, as worked out in Plato's later dialogues and the logical treatises of Aristotle, has arisen.
The "inductive arguments" mean the characteristic attempts to arrive at such formulations by the consideration of simple and striking concrete illustrations familiar to us from both Xenophon and Plato, the perpetual arguments about "shoemakers and car penters and fullers," which the fashionable speakers in Plato profess to think vulgar. Induction, on this view of it, is not re garded as a method of proof. Its function is that of suggestion; it puts the meaning of a proposed "definition" forcibly and clearly bef ore the mind. The justification of the definition, then, has to be sought in a consideration of the satisfactoriness of the "consequences," which would follow from its adoption. Socrates himself sought for his "definitions" principally in the sphere in which he was most interested, that of conduct, private and public. As Aristotle says, he concerned himself with the "ethical," char acter and conduct, not with "nature" at large. This is what Cicero means by saying that he "brought down philosophy from heaven to earth." Before him cosmology had been the chief topic of interest, after him, the central problem of philosophy was to formulate a rule of life. With him the "practical use of reason" comes by its rights. In this respect Socrates stamped on philosophy a character which it has never lost. The main outlines of his philos ophy of conduct are fortunately quite certain, and could be dis covered if we had no more material than the Platonic Apology and the Memorabilia of Xenophon. As the Apology tells us, the specific message from God which Socrates brought to his fellow men was that it is the great business of life to practice the "care" or "tendance" (irt,uaaa, Oeparela), of one's soul, to "make one's soul as good as possible," and not to ruin one's life, as most men do, by putting care for the body or for "possessions" before care for the "soul." The thought which is here fundamental is that of the "soul" as that which is most truly a man's self. In Greek literature, down to the end of the 5th century, we can trace two main senses of the word Ikvxii. (I) It means "the breath of life" which a man parts with in dying. It is this which, in popular superstition, is left as a mere "ghost," or "shade," when the man "himself," his body, has perished. In earlier Ionian science this is identified with the "air" which a man inhales so long as he is alive. (2) In circles influenced by the Orphic religion the soul is thought of as something which has a destiny beyond the grave, but this, too, is something different from the self. It is a sort of stranger inhabiting the body, but having little to do with the conduct of normal life. It "sleeps while the body is active, but wakes when the body sleeps," and re veals itself chiefly in dream and trance. From the beginning of the 4th century we find coming at last to mean what "soul" means to us, the normal waking personality, the seat of char acter and intelligence, "that," as Socrates says in Plato, "in virtue of which we are called wise or foolish, good or bad," and as this usage of the word first appears in writers whom we know to have been influenced by Socrates (Isocrates, Plato and Xeno phon), we may fairly ascribe it to his influence. The thought now works out thus. The soul is the man (in the later Academic formulation a man is "a soul using a body").