Theodorus 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, 180a 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, 180b 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.

Socrates 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.

Theodorus THEO. What pupils, my good man? Such people do not become 180c 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.

Socrates 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 180d 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, 180e So that it is motionless, the name of which is the All,^{1 2} 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, 181a 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. ³ 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. 181b 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.

Theodorus THEO. Oh, it would be unendurable, Socrates, not to examine thoroughly the doctrines of both parties.

Socrates 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: 181c 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?

Theodorus THEO. Yes.

Socrates SOC. Let this, then, be one kind of motion. Now when a thing 181d 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?

Theodorus THEO. I think so.

Socrates SOC. Nay, it must be true. So I say that there are these two kinds of motion: “alteration,” and “motion in space.”

Theodorus THEO. And you are right.

Socrates 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, 181e moving in space and undergoing alteration, or one thing in both ways and another in one of the two ways only?”

Theodorus THEO. By Zeus, I cannot tell! But I think they would say that everything moves in both ways.

Socrates 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.

Theodorus THEO. What you say is very true.

Socrates SOC. Then since they must be in motion, and since absence of motion must be impossible for anything, all things are 182a always in all kinds of motion.

Theodorus THEO. Necessarily.

Socrates 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. 182b 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.

Theodorus THEO. I remember, of course.

Socrates SOC. Let us then pay no attention to other matters, whether they teach 182c 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?

Theodorus THEO. Yes.

Socrates SOC. Have they then both kinds of motion which we distinguished? Are they moving in space and also undergoing alteration?

Theodorus THEO. Of course; that is, if they are to be in perfect motion.

Socrates 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?

Theodorus THEO. That is right.

Socrates 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?

Theodorus 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?

Socrates 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 182e seeing or hearing?

Theodorus THEO. It must be impossible, if all things are in motion.

Socrates 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.

Theodorus THEO. No, we must not.

Socrates SOC. And yet perception is knowledge, as Theaetetus and I said.

Theodorus THEO. Yes, you did say that.

Socrates SOC. Then when we were asked “what is knowledge?” we answered no more what knowledge is than what not-knowledge is.