Theaetetus (179)

SOC. Yes, my friend, he certainly did; otherwise nobody would have paid him a high fee for his conversations, if he had not made his pupils believe that neither a prophet nor anyone else could judge better than himself what was in the future to be and seem.

THEO. Very true.

SOC. Both lawmaking, then, and the advantageous are concerned with the future, and everyone would agree that a state in making laws must often fail to attain the greatest advantage?

THEO. Assuredly.

SOC. Then it will be a fair answer if we say to your master that he is obliged to agree that one man is wiser than another, and that such a wise man is a measure, but that I, who am without knowledge, am not in the least obliged to become a measure, as the argument in his behalf just now tried to oblige me to be, whether I would or no.

THEO. In that respect, Socrates, I think that the argument is most clearly proved to be wrong, and it is proved wrong in this also, in that it declares the opinions of others to be valid, whereas it was shown that they do not consider his arguments true at all.

SOC. In many other respects, Theodorus, it could be proved that not every opinion of every person is true, at any rate in matters of that kind; but it is more difficult to prove that opinions are not true in regard to the momentary states of feeling of each person, from which our perceptions and the opinions concerning them arise. But perhaps I am quite wrong; for it may be impossible to prove that they are not true, and those who say that they are manifest and are forms of knowledge may perhaps be right, and Theaetetus here was not far from the mark in saying that perception and knowledge are identical. So we must, as the argument in behalf of Protagoras [*] enjoined upon us, come up closer and examine this doctrine of motion as the fundamental essence, rapping on it to see whether it rings sound or unsound. As you know, a strife has arisen about it, no mean one, either, and waged by not a few combatants.

THEO. Yes, far from mean, and it is spreading far and wide all over Ionia; for the disciples of Heracleitus are supporting this doctrine very vigorously.

SOC. Therefore, my dear Theodorus, we must all the more examine it from the beginning as they themselves present it.