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. SOC. He will, I fancy, say all that we have said in his defence

 
and then will close with us, saying contemptuously, Our estimable Socrates here frightened a little boy by asking if it was possible for one and the same person to remember and at the same time not to know one and the same thing, and when the child in his fright said no, because he could not foresee what would result, Socrates made poor me a laughing-stock in his talk. But, you slovenly Socrates, the facts stand thus: when you examine any doctrine of mine by the method of questioning, if the person who is questioned makes such replies as I should make and comes to grief, then I am refuted,
 
but if his replies are quite different, then the person questioned is refuted, not I. Take this example. Do you suppose you could get anybody to admit that the memory a man has of a past feeling he no longer feels is anything like the feeling at the time when he was feeling it? Far from it. Or that he would refuse to admit that it is possible for one and the same person to know and not to know one and the same thing? Or if he were afraid to admit this, would he ever admit that a person who has become unlike is the same as before he became unlike? In fact, if we are to be on our guard against such verbal entanglements, would he admit that a person is one at all, and not many, who become infinite in number,
 
if the process of becoming different continues? But, my dear fellow, he will say, attack my real doctrines in a more generous manner, and prove, if you can, that perceptions, when they come, or become, to each of us, are not individual, or that, if they are individual, what appears to each one would not, for all that, become to that one alone—or, if you prefer to say be, would not be—to whom it appears. But when you talk of pigs and dog-faced baboons, you not only act like a pig yourself, but you persuade your hearers to act so toward my writings,
 
and that is not right. For I maintain that the truth is as I have written; each one of us is the measure of the things that are and those that are not; but each person differs immeasurably from every other in just this, that to one person some things appear and are, and to another person other things. And I do not by any means say that wisdom and the wise man do not exist; on the contrary, I say that if bad things appear and are to any one of us, precisely that man is wise who causes a change and makes good things appear and be to him. 
 
And, moreover, do not lay too much stress upon the words of my argument, but get a clearer understanding of my meaning from what I am going to say. Recall to your mind what was said before, that his food appears and is bitter to the sick man, but appears and is the opposite of bitter to the man in health.