Last Updated on May 6, 2015, by eNotes Editorial. Word Count: 665
After a digression, Socrates turns to a more serious criticism of the position of Protagoras, one that takes into account the justification Socrates has offered on behalf of Protagoras. Socrates is quite willing to admit that the Protagorean position is a fair account of what occurs in immediate sensation. The world of becoming, for Plato and Socrates, is a flux, and people’s sensations are private. One cannot taste the apple another person is tasting, nor does one ever see a particular apple tree from quite the same perspective as that of one’s companion. The “seeming” of the immediate data of sense is the “reality” of the immediate data of sense. However, the problem of knowledge is wider than the problem of data.
A theory of knowledge must account for other judgments besides those concerning the immediate data of sense, and it is this fact that finally undercuts the Protagorean theory. Once one recognizes that there is more to the problem of knowing than merely giving an account of the direct awareness of uninterpreted sense experience, the weakness of the Protagorean position becomes obvious. Socrates raises the question of justifying judgments that have a future reference; thus, he broadens the scope of the discussion to include a problem Protagoras’s theory cannot explain. A physician and his patient, for example, may disagree today about whether the patient will have a fever tomorrow. It is clear that both cannot be judging truly, and obviously the physician’s prediction is more reliable than is the patient’s. Both are judging about a fact that is not at the moment a part of the immediate experience of either of them, and both cannot be right in their judgments; clearly one of them (the physician) is a better “measure” than is the other. When the consideration of knowing is thus broadened to include more than merely people’s immediate experience, the Protagorean theory is seen to be inadequate.
Socrates next moves to a more critical examination of the doctrine that the world of sense experience is a flux. He examines the position of the followers of Heraclitus. Heraclitus had said that everything is in flux and that a person cannot step into the same river twice since “new waters are ever flowing.” Some of his followers, however, had gone beyond this claim in saying that one cannot step into the same river even once. What these followers sensed, apparently, was that if everything is an absolute flux, then there is no point at all to mentioning “same.” “Same” is a word that has meaning only in contrast with change, but if all is utter change, there is nothing that can be said to be “the same.” This doctrine meshes well with the Protagorean doctrine; in fact, it is the Protagorean position stated in its most extreme form. Socrates therefore wishes to consider it.
The crucial point that the Heraclitean analysis omits is the recognition that there must be something that is exempt from the flux if there is to be any knowledge at all. If the world is nothing but a flux, in this extreme Heraclitean sense, then knowledge is impossible. Socrates rejects both the unrelieved flux of the extreme Heracliteans and its opposite number, the unchanging unity of the followers of Parmenides. Knowledge, in the strict sense, is of elements like the Parmenidean One, but the (almost) knowledge we have of the world of becoming is of a flux that moves within limits that are unchanging and fixed after the manner of the Parmenidean unity. The world of sense experience, for Plato, is a flux—as the Heracliteans recognized—but insofar as this world of sense experience can be known, it must be viewed against an unchanging set of limits having the character of the Parmenidean One. Knowledge of the world of sense experience, then, involves both the changing and the unchanging; neither is by itself sufficient to account for our knowledge. Absolute flux is radically unknowable.