179
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 See 168 B. 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.
179
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.
179
SOC. Therefore, my dear Theodorus, we must all the more examine it from the beginning as they themselves present it.