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376 HISTORY OF GREECE. into the mouth of the opponent, we ought to be cautious of con- demning the latter upon such very dubious proof. Welcker and other modern authors treat Prodikus as "the most innocent" of the sophists, and except him from the sentence which they pass upon the class generally. Let us see, therefore, what Plato himself says about the rest of them, and first about Protagoras. If it were not the established practice with readers of Plato to condemn Protagoras beforehand, and to put upon every passage relating to him not only a sense as bad as it will bear, but much worse than it will fairly bear, they would prob- ably carry away very diflbrent inferences from the Platonic dialogue called by that sophist's name, and in which he is made to bear a chief part. That dialogue is itself enough to prove that Plato did not conceive Proiagoras either as a corrupt, or unwor- thy, or incompetent teacher. The course of the dialogue exhibits him as not master of the theory of ethics, and unable to solve various difficulties with which that theory is expected to grapple ; moreover, as no match for Sokrates in dialectics, which Plato con- sidered as the only efficient method of philosophical investigation. In so far, therefore, as imperfect acquaintance with the science or theory upon which rules of art, or the precepts bearing on practice, repose, disqualifies a teacher from giving instruction in such art or practice, to that extent Protagoras is exposed as wanting. And if an expert dialectician, like Plato, had passed Isokrates or Quintilian, or the large majority of teachers past or present, through a similar cross-examination as to the theory of their teaching, an ignorance not less manifest than that of Pro- tagoras would be brought out. The antithesis which Plato sets forth, in so many of his dialogues, between precept or practice, accompanied by full knowledge of the scientific principles from which it must be deduced, if its rectitude be disputed, and un- scientific practice, without any such power of deduction or de- fence, is one of the most valuable portions of his speculations : he exhausts his genius to render it conspicuous in a thousand indirect ways, and to shame his readers, if possible, into the loftier and more rational walk of thought. But it is one thing to say of a man, that he does not know the theory of what he teaches, or of the way in which he teaches ; it is another thing tc Bay, that he actually teaches that which scientific theory would