[Footnote 30: Plato, Sophist. pp. 232-233 C, 235 A. Sokrates tells us in the Platonic Apology (p. 23 A) that this was the exact effect which his own cross-examination produced upon the hearers: they supposed him to be wise on those topics on which he exposed ignorance in others. The Memorabilia of Xenophon exhibit the same impression as made by the conversation of Sokrates, even when he talked with artisans on their own arts. Sokrates indeed professed not to teach anyone--and he certainly took no fee for teaching. But we see plainly that this disclaimer imposed upon no one; that he did teach, though gratuitously; and that what he taught was, the art of cross-examination and dispute. We learn this not merely from his enemy, Aristophanes, and from the proceedings of his opponents, Kritias and Charikles (Xenoph. Memor. i. 2), but also from his own statement in the Platonic Apology (pp. 23 C. 37 E. 39 B), and from the language of Plato and Xenophon throughout. Plato is here puzzled to make out a clear line of distinction between the Elenchus of Sokrates, and the disputatious arguments of those Sophists whom he calls Eristic--name deserved quite as much by Sokrates as by any of them. Plato here accuses the Sophists of talking upon a great many subjects which they did not know, and teaching their pupils to do the same. This is exactly what Sokrates passed his life in doing, and what he did better than any one--on the negative side.] [Footnote 31: Plato, Sophist. pp. 235-236.] [Side-note: Doubt started by the Eleate. How can it be possible either to think or to speak falsely?] Here however (continues Plato) we are involved in a difficulty. How can a thing appear to be what it is not? How can a man who opines or affirms, opine or affirm falsely--that is, opine or affirm the thing that is not? To admit this, we must assume the thing that is not (or Non-Ens, Nothing) to have a real existence. Such an assumption involves great and often debated difficulties. It has been pronounced by Parmenides altogether inadmissible.[32] [Footnote 32: Plato, Sophist. pp. 236 E--237 A. [Greek: pa/nta tau=ta e)sti mesta\ a)pori/as a)ei\ e)n tô=| pro/sthen chro/nô| kai\ nu=n. O(/pôs ga\r ei)po/nta chrê\ pseudê= le/gein ê)\ doxa/zein o)/ntôs ei)=nai, kai\ tou=to phthegxa/menon e)nantiologi/a| mê\ xune/chesthai, panta/pasi chalepo/n . . . Teto/lmêken o( lo/gos ou(=tos u(pothe/sthai to\ mê\ o)\n ei)=nai; pseu=dos ga\r ou)k a)\n a)/llôs e)gi/gneto o)/n.]] We have already seen that Plato discussed this same question in the Theætêtus, and that after trying and rejecting many successive hypotheses to show how false supposition, or false affirmation, might be explained as possible, by a theory involving no contradiction, he left the question unsolved. He now resumes it at great length. It occupies more than half[33] the dialogue. Near the close, but only then, he reverts to the definition of the Sophist. [Footnote 33: From p. 236 D to p. 264 D.]