SEC. 24. The nihilistic doctrine of Gorgias of Leontini,[33] who taught that nothing exists, that if it did exist it could not be known, and that if it did exist and could be known the knowledge of it could not be communicated by one mind to another, is founded in part upon such bad reasoning that it is rather surprising that Gorgias should have been guilty of it. That part of it, however, which has to do with the communicability of knowledge is rather better than the rest, and indicates some progress in reflection. A sign, he says, differs from the thing it signifies. How can one communicate the notion of color by words, since the ear hears sounds and not colors? Besides, how can the same idea be in two different persons? This reasoning would seem at least plausible, I think, to many minds at the present day. It is evidently the offspring of a confusion of samenesses. A sign differs, it is true, from the thing signified. The word blue heard by the ear is not like the color blue seen or imagined. But if any one pronounce the word, and ask me if I am thinking of the color he has mentioned, I say yes. The sound is not like the color, but it is its representative, and one of the proper uses of the word same (the fifth) indicates just this relation between representative and thing represented. Any attempt to discredit communication of knowledge on the ground that one cannot speak colors, and that, therefore, one man is speaking one thing and the other thinking another, goes on the supposition that what is said and what is thought must be the same in sense first (strict identity) or in sense fourth (must be a thing of the same kind). And as to the existence of the same thing in two minds; here Gorgias has evidently discovered with some surprise that sameness in sense sixth differs from sameness in sense first, and has felt impelled to deny it the name altogether. He has perceived a duality where most men have not noticed it; and, instead of observing that there are samenesses and samenesses, and that the communication of knowledge is concerned with the sixth kind in this connection, and not with the first, he has denied the communication of knowledge. Had he found it necessary to carry out his theoretic premises to practical conclusions he would have stopped talking, which he did not; though presumably the irrepressible didactic instinct would have led him, spite of consistency, to imitate Cratylus in moving his finger. [33] Ueberweg. Hist. of Philos., Vol. I, § 29, p. 77.