Str. This point, then, let us put down definitely as one of complete perplexity. But since being and not-being participate equally in the perplexity, there is now at last some hope that as either of them emerges more dimly or more clearly, so also will the other emerge. 
 If, however, we are able to see neither of them, we will at any rate push our discussion through between both of them at once as creditably as we can. Theaet. Good. Str. Let us, then, explain how we come to be constantly calling this same thing by many names. Theaet. What, for instance? Please give an example. Str. We speak of man, you know, and give him many additional designations; we attribute to him colors and forms and sizes and vices and virtues,
 and in all these cases and countless others we say not only that he is man, but we say he is good and numberless other things. So in the same way every single thing which we supposed to be one, we treat as many and call by many names. Theaet. True. Str. And it is in this way, I fancy, that we have provided a fine feast for youngsters and for old men whose learning has come to them late in life; for example, it is easy enough for anyone to grasp the notion that the many cannot possibly be one, nor the one many, and so, apparently, they take pleasure in saying that we must not call a man good,
 but must call the good good, and a man man. I fancy, Theaetetus, you often run across people who take such matters seriously; sometimes they are elderly men whose poverty of intellect makes them admire such quibbles, and who think this is a perfect mine of wisdom they have discovered. Those are here satirized who deny the possibillty of all except identical predication. Such were Antisthenes, Euthydemus, and Dionysodorus. The two last are probably those referred to as old men whose learning came late in life. Theaet. Certainly. Str. Then, to include in our discussion all those who have ever engaged in any talk whatsoever about being,
 let us address our present arguments to these men as well as to all those with whom we were conversing before, and let us employ the form of questions. Theaet. What are the arguments? Str. Shall we attribute neither being to rest and motion, nor any attribute to anything, but shall we in our discussions assume that they do not mingle and cannot participate in one another? Or shall we gather all things together, believing that they are capable of combining with one another? Or are some capable of it and others not? Which of these alternatives,
 Theaetetus, should we say is their choice? Theaet. I cannot answer these questions for them. Str. Then why did you not answer each separately and see what the result was in each case? Theaet. A good suggestion. Str. And let us, if you please, assume that they say first that nothing has any power to combine with anything else. Then motion and rest will have no share in being, will they? Theaet. No. Str. Well, then, will either of them be, if it has no share in being? Theaet. It will not. Str. See how by this admission everything is overturned at once, as it seems—the doctrine of those who advocate universal motion, that of the partisans of unity and rest, and that of the men who teach that all existing things are distributed into invariable and everlasting kinds. For all of these make use of being as an attribute. One party says that the universe is in motion, another that it is at rest. Theaet. Exactly. Str. And further, all who teach that things combine at one time and separate at another, whether infinite elements combine in unity and are derived from unity or finite elements separate and then unite, regardless of whether they say that these changes take place successively or without interruption, would be talking nonsense in all these doctrines, if there is no intermingling. Theaet. Quite right. Str. Then, too, the very men who forbid us to call anything by another name because it participates in the effect produced by another, would be made most especially ridiculous by this doctrine. Theaet. How so? Str. Because they are obliged in speaking of anything to use the expressions to be, apart, from the rest, by itself, and countless others; they are powerless to keep away from them or avoid working them into their discourse; and therefore there is no need of others to refute them, but, as the saying goes, their enemy and future opponent is of their own household whom they always carry about with them as they go, giving forth speech from within them, like the wonderful Eurycles. Eurycles was a ventriloquist and soothsayer of the fifth century, cf. Aristoph. Wasps 1019 Theaet. That is a remarkably accurate illustration Str. But what if we ascribe to all things the power of participation in one another? Theaet. Even I can dispose of that assumption. Str. How? Theaet. Because motion itself would be wholly at rest, and rest in turn would itself be in motion, if these two could be joined with one another. Str. But surely this at least is most absolutely impossible, that motion be at rest and rest be in motion? Theaet. Of course. Str. Then only the third possibility is left. Theaet. Yes. Str. And certainly one of these three must be true; either all things will mingle with one another, or none will do so, or some will and others will not. Theaet. Of course. Str. And certainly the first two were found to be impossible. Theaet. Yes. Str. Then everybody who wishes to answer correctly will adopt the remaining one of the three possibilities. Theaet. Precisely. Str. Now since some things will commingle and others will not,
 they are in much the same condition as the letters of the alphabet; for some of these do not fit each other, and others do. Theaet. Of course. Str. And the vowels, to a greater degree than the others, run through them all as a bond, so that without one of the vowels the other letters cannot be joined one to another. Theaet. Certainly. Str. Now does everybody know which letters can join with which others? Or does he who is to join them properly have need of art? Theaet. He has need of art. Str. What art? Theaet. The art of grammar. Str. And is not the same true in connection with high and
 low sounds? Is not he who has the art to know the sounds which mingle and those which do not, musical, and he who does not know unmusical? Theaet. Yes. Str. And we shall find similar conditions, then, in all the other arts and processes which are devoid of art? Theaet. Of course. Str. Now since we have agreed that the classes or genera also commingle with one another, or do not commingle, in the same way, must not he possess some science and proceed by the processes of reason who is to show correctly which of the classes harmonize with which, and which reject one another,
 and also if he is to show whether there are some elements extending through all and holding them together so that they can mingle, and again, when they separate, whether there are other universal causes of separation? Theaet. Certainly he needs science, and perhaps even the greatest of sciences. Str. Then, Theaetetus, what name shall we give to this science? Or, by Zeus, have we unwittingly stumbled upon the science that belongs to free men and perhaps found the philosopher while we were looking for the sophist? Theaet. What do you mean? Str. Shall we not say that the division of things by classes and the avoidance of the belief that the same class is another, or another the same, belongs to the science of dialectic? Theaet. Yes, we shall. Str. Then he who is able to do this has a clear perception of one form or idea extending entirely through many individuals each of which lies apart, and of many forms differing from one another but included in one greater form, and again of one form evolved by the union of many wholes,
 and of many forms entirely apart and separate. This is the knowledge and ability to distinguish by classes how individual things can or cannot be associated with one another. Theaet. Certainly it is. Str. But you surely, I suppose, will not grant the art of dialectic to any but the man who pursues philosophy in purity and righteousness. Theaet. How could it be granted to anyone else? Str. Then it is in some region like this that we shall always, both now and hereafter, discover the philosopher, if we look for him; 
 he also is hard to see clearly, but the difficulty is not the same in his case and that of the sophist. Theaet. How do they differ? Str. The sophist runs away into the darkness of not-being, feeling his way in it by practice, By practice, i.e., by empirical knowledge as opposed to reason. and is hard to discern on account of the darkness of the place. Don’t you think so? Theaet. It seems likely. Str. But the philosopher, always devoting himself through reason to the idea of being, is also very difficult to see on account of the brilliant light of the place; for the eyes
 of the soul of the multitude are not strong enough to endure the sight of the divine. Theaet. This also seems no less true than what you said about the sophist. Str. Now we will make more accurate investigations about the philosopher hereafter, if we still care to do so; but as to the sophist, it is clear that we must not relax our efforts until we have a satisfactory view of him. Theaet. You are right. Str. Since, therefore, we are agreed that some of the classes will mingle with one another, and others will not, and some will mingle with few and others with many, and that
 there is nothing to hinder some from mingling universally with all, let us next proceed with our discussion by investigating, not all the forms or ideas, lest we become confused among so many, but some only, selecting them from those that are considered the most important; let us first consider their several natures, then what their power of mingling with one another is, and so, if we cannot grasp being and not-being with perfect clearness, we shall at any rate not fail to reason fully about them, so far as the method of our present inquiry permits. Let us in this way see whether it is, after all,
 permitted us to say that not-being really is, although not being, and yet come off unscathed. Theaet. Yes; that is the proper thing for us to do. Str. The most important, surely, of the classes or genera are those which we just mentioned; being itself and rest and motion. Theaet. Yes, by far. Str. And further, two of them, we say, cannot mingle with each other. Theaet. Decidedly not. Str. But being can mingle with both of them, for they both are. Theaet. Of course. Str. Then these prove to be three. Theaet. To be sure. Str. Each of them is, then, other than the remaining two, but the same as itself. Theaet. Yes. Str. But what do we mean by these words, the same and other, which we have just used? Are they two new classes, different from the other three, but always of necessity mingled with them, and must we conduct our inquiry on the assumption that there are five classes, not three, or are we unconsciously speaking of one of those three
 when we say the same or other ? Theaet. Perhaps. Str. But certainly motion and rest are neither other nor the same. Theaet. How so? Str. Whatever term we apply to rest and motion in common cannot be either of those two. Theaet. Why not? Str. Because motion would be at rest and rest would be in motion; in respect of both, for whichever of the two became other would force the other to change its nature into that of its opposite, since
 it would participate in its opposite. Theaet. Exactly so. Str. Both certainly partake of the same and the other. i.e., sameness and difference can he predicated of both. Theaet. Yes. Str. Then we must not say that motion, or rest either, is the same or other. Theaet. No. Str. But should we conceive of being and the same as one? Theaet. Perhaps. Str. But if being and the same have no difference of meaning, then when we go on and say that both rest and motion are, we shall be saying that they are both the same,
 since they are. Theaet. But surely that is impossible. Str. Then it is impossible for being and the same to be one. Theaet. Pretty nearly. Str. So we shall consider the same a fourth class in addition to the other three? Theaet. Certainly. Str. Then shall we call the other a fifth class? Or must we conceive of this and being as two names for one class? Theaet. May be. Str. But I fancy you admit that among the entities some are always conceived as absolute, and some as relative. Theaet. Of course. Str. And other is always relative to other, is it not? Theaet. Yes. Str. It would not be so, if being and the other were not utterly different. If the other, like being, partook of both absolute and relative existence, there would be also among the others that exist another not in relation to any other; but as it is, we find that whatever is other is just what it is through compulsion of some other. Theaet. The facts are as you say. Str. Then we must place the nature of the other as a fifth
 among the classes in which we select our examples. Theaet. Yes. Str. And we shall say that it permeates them all; for each of them is other than the rest, not by reason of its own nature, but because it partakes of the idea of the other. Theaet. Exactly. Str. Let us now state our conclusions, taking up the five classes one at a time. Theaet. How? Str. Take motion first; we say that it is entirely other than rest, do we not? Theaet. We do. Str. Then it is not rest. Theaet. Not at all.