Theaetetus

SOC. Then I shall never have this perception of any other thing; for a perception of another thing is another perception, and makes the percipient different and other: nor can that which acts on me ever by union with another produce the same result or become the same in kind; for by producing another result from another passive element it will become different in kind.

THEAET. That is true.

SOC. And neither shall I, furthermore, ever again become the same as I am, nor will that ever become the same as it is.

THEAET. No.

SOC. And yet, when I become percipient, I must necessarily become percipient of something, for it is impossible to become percipient and perceive nothing; and that which is perceived must become so to someone, when it becomes sweet or bitter or the like; for to become sweet, but sweet to no one, is impossible.

THEAET. Perfectly true.

SOC. The result, then, I think, is that we (the active and the passive elements) are or become, whichever is the case, in relation to one another, since we are bound to one another by the inevitable law of our being, but to nothing else, not even to ourselves. The result, then, is that we are bound to one another; and so if a man says anything is, he must say it is to or of or in relation to something, and similarly if he says it becomes; but he must not say it is or becomes absolutely, nor can he accept such a statement from anyone else. That is the meaning of the doctrine we have been describing.

THEAET. Yes, quite so, Socrates.

SOC. Then, since that which acts on me is to me and to me only, it is also the case that I perceive it, and I only?

THEAET. Of course.

SOC. Then to me my perception is true; for in each case it is always part of my being; and I am, as Protagoras says, the judge of the existence of the things that are to me and of the non-existence of those that are not to me.

THEAET. So it seems.

SOC. How, then, if I am an infallible judge and my mind never stumbles in regard to the things that are or that become, can I fail to know that which I perceive?

THEAET. You cannot possibly fail.

SOC. Therefore you were quite right in saying that knowledge is nothing else than perception, and there is complete identity between the doctrine of Homer and Heracleitus and all their followers—that all things are in motion, like streams—the doctrine of the great philosopher Protagoras that man is the measure of all things—and the doctrine of Theaetetus that, since these things are true, perception is knowledge. Eh, Theaetetus? Shall we say that this is, so to speak, your new-born child and the result of my midwifery? Or what shall we say?

THEAET. We must say that, Socrates.

SOC. Well, we have at last managed to bring this forth, whatever it turns out to be; and now that it is born, we must in very truth perform the rite of running round with it in a circle— [*](The rite called amphidromiatook place a few days after the birth of a child. After some ceremonies of purification the nurse, in the presence of the family, carried the infant rapidly about the family hearth, thereby introducing him, as it were, to the family and the family deities. At this time the father decided whether to bring up the child or to expose it. Sometimes, perhaps, the child was named on this occasion. In the evening relatives assembled for a feast at which shell-fish were eaten.) the circle of our argument—and see whether it may not turn out to be after all not worth rearing, but only a wind-egg, an imposture. But, perhaps, you think that any offspring of yours ought to be cared for and not put away; or will you bear to see it examined and not get angry if it is taken away from you, though it is your first-born?

THEO. Theaetetus will bear it, Socrates, for he is not at all ill-tempered. But for heaven’s sake, Socrates, tell me, is all this wrong after all?

SOC. You are truly fond of argument, Theodorus, and a very good fellow to think that I am a sort of bag full of arguments and can easily pull one out and say that after all the other one was wrong; but you do not understand what is going on: none of the arguments comes from me, but always from him who is talking with me. I myself know nothing, except just a little, enough to extract an argument from another man who is wise and to receive it fairly. And now I will try to extract this thought from Theaetetus, but not to say anything myself.

THEO. That is the better way, Socrates; do as you say.

SOC. Do you know, then, Theodorus, what amazes me in your friend Protagoras?

THEO. What is it?

SOC. In general I like his doctrine that what appears to each one is to him, but I am amazed by the beginning of his book. I don’t see why he does not say in the beginning of his Truth [*](Truthwas apparently the title, or part of the title, of Protagoras’s book.) that a pig or a dog-faced baboon or some still stranger creature of those that have sensations is the measure of all things. Then he might have begun to speak to us very imposingly and condescendingly, showing that while we were honoring him like a god for his wisdom, he was after all no better in intellect than any other man, or, for that matter, than a tadpole. What alternative is there, Theodorus? For if that opinion is true to each person which he acquires through sensation, and no one man can discern another’s condition better than he himself, and one man has no better right to investigate whether another’s opinion is true or false than he himself, but, as we have said several times, each man is to form his own opinions by himself, and these opinions are always right and true, why in the world, my friend, was Protagoras wise, so that he could rightly be thought worthy to be the teacher of other men and to be well paid, and why were we ignorant creatures and obliged to go to school to him, if each person is the measure of his own wisdom? Must we not believe that Protagoras was playing to the gallery in saying this? I say nothing of the ridicule that I and my science of midwifery deserve in that case,—and, I should say, the whole practice of dialectics, too. For would not the investigation of one another’s fancies and opinions, and the attempt to refute them, when each man’s must be right, be tedious and blatant folly, if the Truth of Protagoras is true and he was not jesting when he uttered his oracles from the shrine of his book?

THEO. Socrates, the man was my friend, as you just remarked. So I should hate to bring about the refutation of Protagoras by agreeing with you, and I should hate also to oppose you contrary to my real convictions. So take Theaetetus again; especially as he seemed just now to follow your suggestions very carefully.

SOC. If you went to Sparta, Theodorus, and visited the wrestling-schools, would you think it fair to look on at other people naked, some of whom were of poor physique, without stripping and showing your own form, too?

THEO. Why not, if I could persuade them to allow me to do so? So now I think I shall persuade you to let me be a spectator, and not to drag me into the ring, since I am old and stiff, but to take the younger and nimbler man as your antagonist.

SOC. Well, Theodorus, if that pleases you, it does not displease me, as the saying is. So I must attack the wise Theaetetus again. Tell me, Theaetetus, referring to the doctrine we have just expounded, do you not share my amazement at being suddenly exalted to an equality with the wisest man, or even god? Or do you think Protagoras’s measure applies any less to gods than to men?

THEAET. By no means; and I am amazed that you ask such a question at all; for when we were discussing the meaning of the doctrine that whatever appears to each one really is to him, I thought it was good; but now it has suddenly changed to the opposite.

SOC. You are young, my dear boy; so you are quickly moved and swayed by popular oratory. For in reply to what I have said, Protagoras, or someone speaking for him, will say, Excellent boys and old men, there you sit together declaiming to the people, and you bring in the gods, the question of whose existence or non-existence I exclude from oral and written discussion, and you say the sort of thing that the crowd would readily accept—that it is a terrible thing if every man is to be no better than any beast in point of wisdom; but you do not advance any cogent proof whatsoever; you base your statements on probability. If Theodorus, or any other geometrician, should base his geometry on probability, he would be of no account at all. So you and Theodorus had better consider whether you will accept arguments founded on plausibility and probabilities in such important matters.

THEAET. That would not be right, Socrates; neither you nor we would think so.

SOC. Apparently, then, you and Theodorus mean we must look at the matter in a different way.

THEAET. Yes, certainly in a different way.

SOC. Well, then, let us look at it in this way, raising the question whether knowledge is after all the same as perception, or different. For that is the object of all our discussion, and it was to answer that question than we stirred up all these strange doctrines, was it not?

THEAET. Most assuredly.

SOC. Shall we then agree that all that we perceive by sight or hearing we know? For instance, shall we say that before having learned the language of foreigners we do not hear them when they speak, or that we both hear and know what they say? And again, if we do not know the letters, shall we maintain that we do not see them when we look at them or that if we really see them we know them?

THEAET. We shall say, Socrates, that we know just so much of them as we hear or see: in the case of the letters, we both see and know the form and color, and in the spoken language we both hear and at the same time know the higher and lower notes of the voice; but we do not perceive through sight or hearing, and we do not know, what the grammarians and interpreters teach about them.

SOC. First-rate, Theaetetus! and it is a pity to dispute that, for I want you to grow. But look out for another trouble that is yonder coming towards us, and see how we can repel it.

THEAET. What is it?

SOC. It is like this: If anyone should ask, Is it possible, if a man has ever known a thing and still has and preserves a memory of that thing, that he does not, at the time when he remembers, know that very thing which he remembers? I seem to be pretty long winded; but I merely want to ask if a man who has learned a thing does not know it when he remembers it.

THEAET. Of course he does, Socrates; for what you suggest would be monstrous.

SOC. Am I crazy, then? Look here. Do you not say that seeing is perceiving and that sight is perception?

THEAET. I do.

SOC. Then, according to what we have just said, the man who has seen a thing has acquired knowledge of that which he has seen?

THEAET. Yes.

SOC. Well, then, do you not admit that there is such a thing as memory?

THEAET. Yes.

SOC. Memory of nothing or of something?

THEAET. Of something, surely.

SOC. Of things he has learned and perceived—that sort of things?

THEAET. Of course.

SOC. A man sometimes remembers what he has seen, does he not?

THEAET. He does.

SOC. Even when he shuts his eyes, or does he forget if he does that?

THEAET. It would be absurd to say that, Socrates.

SOC. We must, though, if we are to maintain our previous argument; otherwise, it is all up with it.

THEAET. I too, by Zeus, have my suspicions, but I don’t fully understand you. Tell me how it is.

SOC. This is how it is: he who sees has acquired knowledge, we say, of that which he has seen; for it is agreed that sight and perception and knowledge are all the same.

THEAET. Certainly.

SOC. But he who has seen and has acquired knowledge of what he saw, if he shuts his eyes, remembers it, but does not see it. Is that right?

THEAET. Yes.

SOC. But does not see is the same as does not know, if it is true that seeing is knowing.

THEAET. True.

SOC. Then this is our result. When a man has acquired knowledge of a thing and still remembers it, he does not know it, since he does not see it; but we said that would be a monstrous conclusion.

THEAET. Very true.

SOC. So, evidently, we reach an impossible result if we say that knowledge and perception are the same.

THEAET. So it seems.

SOC. Then we must say they are different.

THEAET. I suppose so.

SOC. Then what can knowledge be? We must, apparently, begin our discussion all over again. And yet, Theaetetus, what are we on the point of doing?

THEAET. About what?

SOC. It seems to me that we are behaving like a worthless game-cock; before winning the victory we have leapt away from our argument and begun to crow.

THEAET. How so?

SOC. We seem to be acting like professional debaters; we have based our agreements on the mere similarity of words and are satisfied to have got the better of the argument in such a way, and we do not see that we, who claim to be, not contestants for a prize, but lovers of wisdom, are doing just what those ingenious persons do.

THEAET. I do not yet understand what you mean.

SOC. Well, I will try to make my thought clear. We asked, you recollect, whether a man who has learned something and remembers it does not know it. We showed first that the one who has seen and then shuts his eyes remembers, although he does not see, and then we showed that he does not know, although at the same time he remembers; but this, we said, was impossible. And so the Protagorean tale was brought to naught, and yours also about the identity of knowledge and perception.

THEAET. Evidently.

SOC. It would not be so, I fancy, my friend, if the father of the first of the two tales were alive; he would have had a good deal to say in its defence. But he is dead, and we are abusing the orphan. Why, even the guardians whom Protagoras left—one of whom is Theodorus here—are unwilling to come to the child’s assistance. So it seems that we shall have to do it ourselves, assisting him in the name of justice.

THEO. Do so, for it is not I, Socrates, but rather Callias the son of Hipponicus, who is the guardian of his children. As for me, I turned rather too soon from abstract speculations to geometry. However, I shall be grateful to you if you come to his assistance.

SOC. Good, Theodorus! Now see how I shall help him; for a man might find himself involved in still worse inconsistencies than those in which we found ourselves just now, if he did not pay attention to the terms which we generally use in assent and denial. Shall I explain this to you, or only to Theaetetus?

THEO. To both of us, but let the younger answer; for he will be less disgraced if he is discomfited.

SOC. Very well; now I am going to ask the most frightfully difficult question of all. It runs, I believe, something like this: Is it possible for a person, if he knows a thing, at the same time not to know that which he knows?

THEO. Now, then, what shall we answer, Theaetetus?

THEAET. It is impossible, I should think.

SOC. Not if you make seeing and knowing identical. For what will you do with a question from which there is no escape, by which you are, as the saying is, caught in a pit, when your adversary, unabashed, puts his hand over one of your eyes and asks if you see his cloak with the eye that is covered?

THEAET. I shall say, I think, Not with that eye, but with the other.

SOC. Then you see and do not see the same thing at the same time?

THEAET. After a fashion.

SOC.That, he will reply, is not at all what I want, and I did not ask about the fashion, but whether you both know and do not know the same thing. Now manifestly you see that which you do not see. But you have agreed that seeing is knowing and not seeing is not knowing. Very well; from all this, reckon out what the result is.

THEAET. Well, I reckon out that the result is the contrary of my hypothesis.

SOC. And perhaps, my fine fellow, more troubles of the same sort might have come upon you, if anyone asked you further questions—whether it is possible to know the same thing both sharply and dully, to know close at hand but not at a distance, to know both violently and gently, and countless other questions, such as a nimble fighter, fighting for pay in the war of words, might have lain in wait and asked you, when you said that knowledge and perception were the same thing; he would have charged down upon hearing and smelling and such senses, and would have argued persistently and unceasingly until you were filled with admiration of his greatly desired wisdom and were taken in his toils, and then, after subduing and binding you he would at once proceed to bargain with you for such ransom as might be agreed upon between you. What argument, then, you might ask, will Protagoras produce to strengthen his forces? Shall we try to carry on the discussion?

THEAET. By all means.