SOC. One of these was

 
Aristeides, the son of Lysimachus, and there are very many more. When such men come back and beg me, as they do, with wonderful eagerness to let them join me again, the spiritual monitor that comes to me forbids me to associate with some of them, but allows me to converse with others, and these again make progress. Now those who associate with me are in this matter also like women in childbirth; they are in pain and are full of trouble night and day, much more than are the women; and my art can arouse this pain and cause it to cease. Well, that is what happens to them. 
 
But in some cases, Theaetetus, when they do not seem to me to be exactly pregnant, since I see that they have no need of me, I act with perfect goodwill as match-maker and, under God, I guess very successfully with whom they can associate profitably, and I have handed over many of them to Prodicus, and many to other wise and inspired men. Now I have said all this to you at such length, my dear boy, because I suspect that you, as you yourself believe, are in pain because you are pregnant with something within you. Apply, then, to me, remembering that I am the son of a midwife
 
and have myself a midwife’s gifts, and do your best to answer the questions I ask as I ask them. And if, when I have examined any of the things you say, it should prove that I think it is a mere image and not real, and therefore quietly take it from you and throw it away, do not be angry as women are when they are deprived of their first offspring. For many, my dear friend, before this have got into such a state of mind towards me that they are actually ready to bite me, if I take some foolish notion away from them, and they do not believe that I do this in kindness,
 
since they are far from knowing that no god is unkind to mortals, and that I do nothing of this sort from unkindness, either, and that it is quite out of the question for me to allow an imposture or to destroy the true. And so, Theaetetus, begin again and try to tell us what knowledge is. And never say that you are unable to do so; for if God wills it and gives you courage, you will be able. THEAET. Well then, Socrates, since you are so urgent it would be disgraceful for anyone not to exert himself in every way
 
to say what he can. I think, then, that he who knows anything perceives that which he knows, and, as it appears at present, knowledge is nothing else than perception. SOC. Good! Excellent, my boy! That is the way one ought to speak out. But come now, let us examine your utterance together, and see whether it is a real offspring or a mere wind-egg. Perception, you say, is knowledge? THEAET. Yes. SOC. And, indeed, if I may venture to say so, it is not a bad description of knowledge

 
that you have given, but one which Protagoras also used to give. Only, he has said the same thing in a different way. For he says somewhere that man is the measure of all things, of the existence of the things that are and the non-existence of the things that are not. You have read that, I suppose? THEAET. Yes, I have read it often. SOC. Well, is not this about what he means, that individual things are for me such as they appear to me, and for you in turn such as they appear to you —you and I being man ? THEAET. Yes, that is what he says. SOC. It is likely that a wise man is not talking nonsense; so let us follow after him. Is it not true that sometimes, when the same wind blows, one of us feels cold, and the other does not? or one feels slightly and the other exceedingly cold? THEAET. Certainly. SOC. Then in that case, shall we say that the wind is in itself cold or not cold or shall we accept Protagoras’s saying that it is cold for him who feels cold and not for him who does not? THEAET. Apparently we shall accept that. SOC. Then it also seems cold, or not, to each of the two? THEAET. Yes. SOC. But seems denotes perceiving? THEAET. It does. SOC. Then seeming and perception are the same thing in matters of warmth and everything of that sort. For as each person perceives things, such they are to each person. THEAET. Apparently. SOC. Perception, then, is always of that which exists and, since it is knowledge, cannot be false. THEAET. So it seems. SOC. By the Graces! I wonder if Protagoras, who was a very wise man, did not utter this dark saying to the common herd like ourselves, and tell the truth An allusion to the title of Protagoras’s book, Truth . in secret to his pupils. THEAET. Why, Socrates, what do you mean by that? SOC. I will tell you and it is not a bad description, either, that nothing is one and invariable, and you could not rightly ascribe any quality whatsoever to anything, but if you call it large it will also appear to be small, and light if you call it heavy, and everything else in the same way, since nothing whatever is one, either a particular thing or of a particular quality; but it is out of movement and motion and mixture with one another that all those things become which we wrongly say are —wrongly, because nothing ever is, but is always becoming. 
 
And on this subject all the philosophers, except Parmenides, may be marshalled in one line—Protagoras and Heracleitus and Empedocles—and the chief poets in the two kinds of poetry, Epicharmus, in comedy, and in tragedy, Homer, who, in the line 0ceanus the origin of the gods, and Tethys their mother, Hom. Il. 14.201, 302 has said that all things are the offspring of flow and motion; or don’t you think he means that? THEAET. I think he does. SOC. Then who could still contend with such a great host,

 
led by Homer as general, and not make himself ridiculous? THEAET. It is not easy, Socrates. SOC. No, Theaetetus, it is not. For the doctrine is amply proved by this, namely, that motion is the cause of that which passes for existence, that is, of becoming, whereas rest is the cause of non-existence and destruction; for warmth or fire, which, you know, is the parent and preserver of all other things, is itself the offspring of movement and friction, and these two are forms of motion. Or are not these the source of fire? THEAET. Yes, they are. SOC. And furthermore, the animal kingdom is sprung from these same sources. THEAET. Of course. SOC. Well, then, is not the bodily habit destroyed by rest and idleness, and preserved, generally speaking, by gymnastic exercises and motions? THEAET. Yes. SOC. And what of the habit of the soul? Does not the soul acquire information and is it not preserved and made better through learning and practice, which are motions, whereas through rest, which is want of practice and of study,
 
it learns nothing and forgets what it has learned? THEAET. Certainly. SOC. Then the good, both for the soul and for the body, is motion, and rest is the opposite? THEAET. Apparently. SOC. Now shall I go on and mention to you also windless air, calm sea, and all that sort of thing, and say that stillness causes decay and destruction and that the opposite brings preservation? And shall I add to this the all-compelling and crowning argument that Homer by the golden chain Hom. Il. 8.18 ff. especially 26. In this passage Zeus declares that all the gods and goddesses together could not, with a golden chain, drag him from on high, but that if he pulled, he would drag them, with earth and sea, would then bind the chain round the summit of Olympus, and all the rest would hang aloft. This crowning argument is a reductio ad absurdum of the habit of using texts from Homer in support of all kinds of doctrine. refers to nothing else than the sun,
 
and means that so long as the heavens and the sun go round everything exists and is preserved, among both gods and men, but if the motion should stop, as if bound fast, everything would be destroyed and would, as the saying is, be turned upside down? THEAET. Yes, Socrates, I think he means what you say he does. SOC. Then, my friend, you must apply the doctrine in this way: first as concerns vision, the color that you call white is not to be taken as something separate outside of your eyes, nor yet as something inside of them; and you must not assign any place to it,
 
for then it would at once be in a definite position and stationary and would have no part in the process of becoming. THEAET. But what do you mean? SOC. Let us stick close to the statement we made a moment ago, and assume that nothing exists by itself as invariably one: then it will be apparent that black or white or any other color whatsoever is the result of the impact of the eye upon the appropriate motion, and therefore that which we call color

 
will be in each instance neither that which impinges nor that which is impinged upon, but something between, which has occurred, peculiar to each individual. Or would you maintain that each color appears to a dog, or any other animal you please, just as it does to you? THEAET. No, by Zeus, I wouldn’t. SOC. Well, does anything whatsoever appear the same to any other man as to you? Are you sure of this? Or are you not much more convinced that nothing appears the same even to you, because you yourself are never exactly the same? THEAET. Yes, I am much more convinced of the last. SOC. Then, if that with which I compare myself in size, or which I touch,
 
were really large or white or hot, it would never have become different by coming in contact with something different, without itself changing; and if, on the other hand, that which did the comparing or the touching were really large or white or hot, it would not have become different when something different approached it or was affected in some way by it, without being affected in some way itself. For nowadays, my friend, we find ourselves rather easily forced to make extraordinary and absurd statements, as Protagoras and everyone who undertakes to agree with him would say. THEAET. What do you mean? What statements? SOC. Take a little example and you will know all I have in mind. Given six dice, for instance, if you compare four with them, we say that they are more than the four, half as many again, but if you compare twelve with them, we say they are less, half as many; and any other statement would be inadmissible; or would you admit any other? THEAET. Not I. SOC. Well then, if Protagoras, or anyone else, ask you, Theaetetus, can anything become greater or more in any other way than by being increased? what reply will you make? THEAET. If I am to say what I think, Socrates, with reference to
 
the present question, I should say no, but if I consider the earlier question, I should say yes, for fear of contradicting myself. SOC. Good, by Hera! Excellent, my friend! But apparently, if you answer yes it will be in the Euripidean spirit; for our tongue will be unconvinced, but not our mind. Eur. Hipp. 612 ἡ γλῶσσ’ ὀμώμοχ’, ἡ δὲ φρὴν ἀνώμοτος , my tongue has sworn, but my mind is unsworn. THEAET. True. SOC. Well, if you and I were clever and wise and had found out everything about the mind, we should henceforth spend the rest of our time testing each other out of the fulness of our wisdom,
 
rushing together like sophists in a sophistical combat, battering each other’s arguments with counter arguments. But, as it is, since we are ordinary people, we shall wish in the first place to look into the real essence of our thoughts and see whether they harmonize with one another or not at all. THEAET. Certainly that is what I should like.