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 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. 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. THEO. Certainly we must. For it is no more possible, Socrates, to discuss these doctrines of Heracleitus (or, as you say, of Homer or even earlier sages) with the Ephesians themselves—those, at least, who profess to be familiar with them—than with madmen. For they are, quite in accordance with their text-books, in perpetual motion; but as for keeping to an argument or a question and quietly answering and asking in turn,

 
their power of doing that is less than nothing; or rather the words nothing at all fail to express the absence from these fellows of even the slightest particle of rest. But if you ask one of them a question, he pulls out puzzling little phrases, like arrows from a quiver, and shoots them off; and if you try to get hold of an explanation of what he has said, you will be struck with another phrase of novel and distorted wording, and you never make any progress whatsoever with any of them, nor do they themselves with one another, for that matter,
 
but they take very good care to allow nothing to be settled either in an argument or in their own minds, thinking, I suppose, that this is being stationary; but they wage bitter war against the stationary, and, so far as they can, they banish it altogether. SOC. Perhaps, Theodorus, you have seen the men when they are fighting, but have not been with them when they are at peace; for they are no friends of yours; but I fancy they utter such peaceful doctrines at leisure to those pupils whom they wish to make like themselves. THEO. What pupils, my good man? Such people do not become
 
pupils of one another, but they grow up of themselves, each one getting his inspiration from any chance source, and each thinks the other knows nothing. From these people, then, as I was going to say, you would never get an argument either with their will or against it; but we must ourselves take over the question and investigate it as if it were a problem of mathematics. SOC. Yes, what you say is reasonable. Now as for the problem, have we not heard from the ancients, who concealed their meaning from the multitude
 
by their poetry, that the origin of all things is Oceanus and Tethys, flowing streams, and that nothing is at rest and likewise from the modern, who, since they are wiser, declare their meaning openly, in order that even cobblers may hear and know their wisdom and may cease from the silly belief that some things are at rest and others in motion, and, after learning that everything is in motion, may honor their teachers? But, Theodorus, I almost forgot that others teach the opposite of this,
 
 So that it is motionless, the name of which is the All, Parmenides, line 98 (ed. Mullach) In its context the infinitive is necessary; but Plato may have quoted carelessly and may have used the indicative. and all the other doctrines maintained by Melissus and Parmenides and the rest, in opposition to all these they maintain that everything is one and is stationary within itself, having no place in which to move. SO. What shall we do with all these people, my friend? For, advancing little by little, we have unwittingly fallen between the two parties, and,

 
	unless we protect ourselves and escape somehow, we shall pay the penalty, like those in the palaestra, who in playing on the line are caught by both sides and dragged in opposite directions. In the game referred to (called διελκυστίνδα by Pollux, ix. 112) the players were divided into two parties, each of which tried to drag its opponents over a line drawn across the palaestra. I think, then, we had better examine first the one party, those whom we originally set out to join, the flowing ones, and if we find their arguments sound, we will help them to pull us over, trying thus to escape the others; but if we find that the partisans of the whole seem to have truer doctrines, we will take refuge with them from those who would move what is motionless. 
 
But if we find that neither party has anything reasonable to say, we shall be ridiculous if we think that we, who are of no account, can say anything worth while after having rejected the doctrines of very ancient and very wise men. Therefore, Theodorus, see whether it is desirable to go forward into so great a danger. THEO. Oh, it would be unendurable, Socrates, not to examine thoroughly the doctrines of both parties. SOC. Then they must be examined, since you are so urgent. Now I think the starting-point of our examination of the doctrine of motion is this: 
 
Exactly what do they mean, after all, when they say that all things are in motion? What I wish to ask is this: Do they mean to say that there is only one kind of motion or, as I believe, two? But it must not be my belief alone; you must share it also, that if anything happens to us we may suffer it in common. Tell me, do you call it motion when a thing changes its place or turns round in the same place? THEO. Yes. SOC. Let this, then, be one kind of motion. Now when a thing
 
remains in the same place, but grows old, or becomes black instead of white, or hard instead of soft, or undergoes any other kind of alteration, is it not proper to say that this is another kind of motion? THEO. I think so. SOC. Nay, it must be true. So I say that there are these two kinds of motion: alteration, and motion in space. THEO. And you are right. SOC. Now that we have made this distinction, let us at once converse with those who say that all things are in motion, and let us ask them, Do you mean that everything moves in both ways,
 
moving in space and undergoing alteration, or one thing in both ways and another in one of the two ways only? THEO. By Zeus, I cannot tell! But I think they would say that everything moves in both ways. SOC. Yes; otherwise, my friend, they will find that things in motion are also things at rest, and it will be no more correct to say that all things are in motion than that all things are at rest. THEO. What you say is very true. SOC. Then since they must be in motion, and since absence of motion must be impossible for anything, all things are

 
always in all kinds of motion. THEO. Necessarily. SOC. Then just examine this point of their doctrine. Did we not find that they say that heat or whiteness or anything you please arises in some such way as this, namely that each of these moves simultaneously with perception between the active and the passive element, and the passive becomes percipient, but not perception, and the active becomes, not a quality, but endowed with a quality? Now perhaps quality seems an extraordinary word, and you do not understand it when used with general application, so let me give particular examples. 
 
For the active element becomes neither heat nor whiteness, but hot or white, and other things in the same way; you probably remember that this was what we said earlier in our discourse, that nothing is in itself unvaryingly one, neither the active nor the passive, but from the union of the two with one another the perceptions and the perceived give birth and the latter become things endowed with some quality while the former become percipient. THEO. I remember, of course. SOC. Let us then pay no attention to other matters, whether they teach
 
one thing or another; but let us attend strictly to this only, which is the object of our discussion. Let us ask them, Are all things, according to your doctrine, in motion and flux? Is that so? THEO. Yes. SOC. Have they then both kinds of motion which we distinguished? Are they moving in space and also undergoing alteration? THEO. Of course; that is, if they are to be in perfect motion. SOC. Then if they moved only in space, but did not undergo alteration, we could perhaps say what qualities belong to those moving things which are in flux, could we not? THEO. That is right. SOC. But since not even this remains fixed—that the thing in flux flows white, but changes, so that there is a flux of the very whiteness, and a change of color, that it may not in that way be convicted of remaining fixed, is it possible to give any name to a color, and yet to speak accurately? THEO. How can it be possible, Socrates, or to give a name to anything else of this sort, if while we are speaking it always evades us, being, as it is, in flux? SOC. But what shall we say of any of the perceptions, such as seeing or hearing? Does it perhaps remain fixed in the condition of
 
seeing or hearing? THEO. It must be impossible, if all things are in motion. SOC. Then we must not speak of seeing more than not seeing, or of any other perception more than of non-perception, if all things are in all kinds of motion. THEO. No, we must not. SOC. And yet perception is knowledge, as Theaetetus and I said. THEO. Yes, you did say that. SOC. Then when we were asked what is knowledge? we answered no more what knowledge is than what not-knowledge is.