Plato

Both the sensation and the quality "sensed" will therefore be affected by any difference in the pair of slower "motions" which cause them (the "organ" and its "environment"), and each pre cipient, therefore, is confined to his strictly private world, which exists only "for" him. There is no "common" perceived world, and therefore no standard of truth or reality other than the in dividual percipient. A teacher does not aim, any more than a physician, at convincing his pupil of the "falsity" of his judg ments, but at giving him "useful" or healthy convictions in place of harmful or diseased convictions.

'For a detailed discussion of it, see A. E. Taylor, Parmenides, Zeno and Socrates (Transactions of Aristotelian Society, N. S. xvi. 234 ff.) The full discussion of such a theory would demand a thorough study both of the Heracleitean philosophy, which says that there is nothing but motion, and the Eleatic philosophy which says that motion is an illusion. But for our immediate purpose, a more summary argument is sufficient. It is certain that even the relativ ists, who hold that each man is the one infallible "measure" of his present perceptions, do not hold that he is the only and inerrant measure of his future sensations. A physician can often judge bet ter than his patient whether the patient is going to have, e.g., the sensations of an ague. A man's own opinion whether a certain course will be expedient or good for him is often far from being the soundest. We must distinguish carefully between what the mind perceives "through bodily organs"—the data of sense—and the things she apprehends "by herself" (airri ainijs) without "organs." These latter include number, sameness, difference, like ness, unlikeness, being, good, bad, right, wrong, i.e., the great uni versal "categories" of fact and value. These are apprehended not by sense, but by thinking, and as they are the formal element in all knowledge, knowledge must be found not in our sensations, but in "the judgment (avXXoytai.os) of the mind upon" them.

II.

Is knowledge, then, "true judgment"? The statement implies that we know what we mean by "false" judgment, error. But is this the case? Error must not be confused with mere false recog nition, misinterpretation of present sensation, since there are purely intellectual errors, and we find ourselves unable to explain the nature of this kind of error. And, in fact, it is clear that per suasive rhetoric may produce in the hearer judgments which are true, but have no claim to be called knowledge. III. Finally, is

knowledge "true judgment accompanied by discourse (µero. Xlryov), true judgment for which we can give grounds"? This would dis tinguish knowledge from "simple apprehension," and would har monize with the theory of those who hold that knowledge is al ways of complexes, never of their simple constituents. But this doctrine has difficulties of its own, and, in any case, if we say that knowledge is true judgment + "discourse," the "discourse" meant must be a statement of the logical differentia of the object of which I have knowledge. The proposed definition therefore amounts to saying that knowledge is true judgment about an object + knowledge of the differentia of that object, and so is circular.

Sophistes and Politicus.

Formally these two important dia logues are closely connected. They are made to appear as a sequel to the Theaetetus, and a further connection is afforded between them by the fact that both are ostensibly concerned with a prob lem of definition, which is treated by the characteristic Platonic method of repeatedly subdividing a genus until we obtain the definiendum as a sub-species. The real purpose of the Sophistes is logical or metaphysical; it aims at explaining the true nature of negative predication and so disposing of the Eleatic thesis that the temporal and sensible realm, containing, as it does, a negative moment, must be mere unreal illusion. The object of the Politicus is to consider the respective merits of two contrasted forms of government, "personal rule" and "constitutionalism," and to rec ommend the second, particularly in the form of "limited mon archy," as most suitable to the actual condition of mankind. The Sophistes lays the foundations of all subsequent logic, the Politicus those of all "constitutionalism." A more temporary purpose in both dialogues is to illustrate the value of careful classification as a basis for scientific definition. In both dialogues Socrates is almost silent ; his place as chief speaker is taken by an unnamed and very unorthodox Eleatic, who seems to be a purely fictitious character. Plato is, in fact, claiming that he, and not formal logicians of Megara, is the continuator of Parmenides, much as Aristotle in his polemic against Xenocrates claims to be the true successor of Plato.