Theaetetus

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

THEO. Necessarily.

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. 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.

THEO. I remember, of course.

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

THEO. Yes.

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

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

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?

THEO. That is right.

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?

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?

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 seeing or hearing?

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

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.

THEO. No, we must not.

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

THEO. Yes, you did say that.

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

THEO. So it seems.

SOC. This would be a fine result of the correction of our answer, when we were so eager to show that all things are in motion, just for the purpose of making that answer prove to be correct. But this, I think, did prove to be true, that if all things are in motion, every answer to any question whatsoever is equally correct, and we may say it is thus or not thus—or, if you prefer, becomes thus, to avoid giving them fixity by using the word is.

THEO. You are right.

SOC. Except, Theodorus, that I said thus, and not thus; but we ought not even to say thus; for thus would no longer be in motion; nor, again, not thus. For there is no motion in this either; but some other expression must be supplied for those who maintain this doctrine, since now they have, according to their own hypothesis, no words, unless it be perhaps the word nohow. That might be most fitting for them, since it is indefinite.

THEO. At any rate that is the most appropriate form of speech for them.

SOC. So, Theodorus, we have got rid of your friend, and we do not yet concede to him that every man is a measure of all things, unless he be a sensible man; and we are not going to concede that knowledge is perception, at least not by the theory of universal motion, unless Theaetetus here has something different to say.

THEO. An excellent idea, Socrates; for now that this matter is settled, I too should be rid of the duty of answering your questions according to our agreement, since the argument about Protagoras is ended.

THEAET. No, Theodorus, not until you and Socrates have discussed those who say all things are at rest, as you proposed just now.

THEO. A young man like you, Theaetetus, teaching your elders to do wrong by breaking their agreements! No; prepare to answer Socrates yourself for the rest of the argument.

THEAET. I will if he wishes it. But I should have liked best to hear about the doctrine I mentioned.

THEO. Calling Socrates to an argument is calling cavalry into an open plain. [*](A proverbial expression. An open plain is just what cavalry desires.) Just ask him a question and you shall hear.

SOC. Still I think, Theodorus, I shall not comply with the request of Theaetetus.

THEO. Why will you not comply with it?

SOC. Because I have a reverential fear of examining in a flippant manner Melissus and the others who teach that the universe is one and motionless, and because I reverence still more one man, Parmenides. Parmenides seems to me to be, in Homer’s words,

one to be venerated

awful.

THEO. Yes, if that is your opinion, we ought to do so.

SOC. Consider, then, Theaetetus, this further point about what has been said. Now you answered that perception is knowledge, did you not?

THEAET. Yes.

SOC. If, then, anyone should ask you, By what does a man see white and black colors and by what does he hear high and low tones? you would, I fancy, say, By his eyes and ears.

THEAET. Yes, I should.

SOC. The easy use of words and phrases and the avoidance of strict precision is in general a sign of good breeding; indeed, the opposite is hardly worthy of a gentleman, but sometimes it is necessary, as now it is necessary to object to your answer, in so far as it is incorrect. Just consider; which answer is more correct, that our eyes are that by which we see or that through which we see, and our ears that by which or that through which we hear?

THEAET. I think, Socrates, we perceive through, rather than by them, in each case.

SOC. Yes, for it would be strange indeed, my boy, if there are many senses ensconced within us, as if we were so many wooden horses of Troy, and they do not all unite in one power, whether we should call it soul or something else, by which we perceive through these as instruments the objects of perception.

THEAET. I think what you suggest is more likely than the other way.

SOC. Now the reason why I am so precise about the matter is this: I want to know whether there is some one and the same power within ourselves by which we perceive black and white through the eyes, and again other qualities through the other organs, and whether you will be able, if asked, to refer all such activities to the body. But perhaps it is better that you make the statement in answer to a question than that I should take all the trouble for you. So tell me: do you not think that all the organs through which you perceive hot and hard and light and sweet are parts of the body? Or are they parts of something else?

THEAET. Of nothing else.

SOC. And will you also be ready to agree that it is impossible to perceive through one sense what you perceive through another; for instance, to perceive through sight what you perceive through hearing, or through hearing what you perceive through sight?

THEAET. Of course I shall.

SOC. Then if you have any thought about both of these together, you would not have perception about both together either through one organ or through the other.

THEAET. No.

SOC. Now in regard to sound and color, you have, in the first place, this thought about both of them, that they both exist?

THEAET. Certainly.

SOC. And that each is different from the other and the same as itself?

THEAET. Of course.

SOC. And that both together are two and each separately is one?

THEAET. Yes, that also.

SOC. And are you able also to observe whether they are like or unlike each other?

THEAET. May be.

SOC. Now through what organ do you think all this about them? For it is impossible to grasp that which is common to them both either through hearing or through sight. Here is further evidence for the point I am trying to make: if it were possible to investigate the question whether the two, sound and color, are bitter or not, you know that you will be able to tell by what faculty you will investigate it, and that is clearly neither hearing nor sight, but something else.

THEAET. Of course it is,—the faculty exerted through the tongue.

SOC. Very good. But through what organ is the faculty exerted which makes known to you that which is common to all things, as well as to these of which we are speaking—that which you call being and not-being, and the other attributes of things, about which we were asking just now? What organs will you assign for all these, through which that part of us which perceives gains perception of each and all of them?

THEAET. You mean being and not-being, and likeness and unlikeness, and identity and difference, and also unity and plurality as applied to them. And you are evidently asking also through what bodily organs we perceive by our soul the odd and the even and everything else that is in the same category.

SOC. Bravo, Theaetetus! you follow me exactly; that is just what I mean by my question.

THEAET. By Zeus, Socrates, I cannot answer, except that I think there is no special organ at all for these notions, as there are for those others; but it appears to me that the soul views by itself directly what all things have in common.

SOC. Why, you are beautiful, Theaetetus, and not, as Theodorus said, ugly; for he who speaks beautifully is beautiful and good. But besides being beautiful, you have done me a favor by relieving me from a long discussion, if you think that the soul views some things by itself directly and others through the bodily faculties; for that was my own opinion, and I wanted you to agree.

THEAET. Well, I do think so.

SOC. To which class, then, do you assign being; for this, more than anything else, belongs to all things?

THEAET. I assign them to the class of notions which the soul grasps by itself directly.

SOC. And also likeness and unlikeness and identity and difference?

THEAET. Yes.

SOC. And how about beautiful and ugly, and good and bad?

THEAET. I think that these also are among the things the essence of which the soul most certainly views in their relations to one another, reflecting within itself upon the past and present in relation to the future.

SOC. Stop there. Does it not perceive the hardness of the hard through touch, and likewise the softness of the soft?

THEAET. Yes.

SOC. But their essential nature and the fact that they exist, and their opposition to one another, and, in turn, the essential nature of this opposition, the soul itself tries to determine for us by reverting to them and comparing them with one another.

THEAET. Certainly.

SOC. Is it not true, then, that all sensations which reach the soul through the body, can be perceived by human beings, and also by animals, from the moment of birth; whereas reflections about these, with reference to their being and usefulness, are acquired, if at all, with difficulty and slowly, through many troubles, in other words, through education?

THEAET. Assuredly.

SOC. Is it, then, possible for one to attain truth who cannot even get as far as being?

THEAET. No.

SOC. And will a man ever have knowledge of anything the truth of which he fails to attain?

THEAET. How can he, Socrates?

SOC. Then knowledge is not in the sensations, but in the process of reasoning about them; for it is possible, apparently, to apprehend being and truth by reasoning, but not by sensation.

THEAET. So it seems.

SOC. Then will you call the two by the same name, when there are so great differences between them?

THEAET. No, that would certainly not be right.

SOC. What name will you give, then, to the one which includes seeing, hearing, smelling, being cold, and being hot?

THEAET. Perceiving. What other name can I give it?

SOC. Collectively you call it, then, perception?

THEAET. Of course.

SOC. By which, we say, we are quite unable to apprehend truth, since we cannot apprehend being, either.

THEAET. No; certainly not.

SOC. Nor knowledge either, then.

THEAET. No.

SOC. Then, Theaetetus, perception and knowledge could never be the same.

THEAET. Evidently not, Socrates; and indeed now at last it has been made perfectly clear that knowledge is something different from perception.

SOC. But surely we did not begin our conversation in order to find out what knowledge is not, but what it is. However, we have progressed so far, at least, as not to seek for knowledge in perception at all, but in some function of the soul, whatever name is given to it when it alone and by itself is engaged directly with realities.

THEAET. That, Socrates, is, I suppose, called having opinion.

SOC. You suppose rightly, my friend. Now begin again at the beginning. Wipe out all we said before, and see if you have any clearer vision, now that you have advanced to this point. Say once more what knowledge is.

THEAET. To say that all opinion is knowledge is impossible, Socrates, for there is also false opinion; but true opinion probably is knowledge. Let that be my answer. For if it is proved to be wrong as we proceed, I will try to give another, just as I have given this.

SOC. That is the right way, Theaetetus. It is better to speak up boldly than to hesitate about answering, as you did at first. For if we act in this way, one of two things will happen: either we shall find what we are after, or we shall be less inclined to think we know what we do not know at all; and surely even that would be a recompense not to be despised. Well, then, what do you say now? Assuming that there are two kinds of opinion, one true and the other false, do you define knowledge as the true opinion?

THEAET. Yes. That now seems to me to be correct.

SOC. Is it, then, still worth while, in regard to opinion, to take up again—?

THEAET. What point do you refer to?

SOC. Somehow I am troubled now and have often been troubled before, so that I have been much perplexed in my own reflections and in talking with others, because I cannot tell what this experience is which we human beings have, and how it comes about.

THEAET. What experience?

SOC. That anyone has false opinions. And so I am considering and am still in doubt whether we had better let it go or examine it by another method than the one we followed a while ago.

THEAET. Why not, Socrates, if there seems to be the least need of it? For just now, in talking about leisure, you and Theodorus said very truly that there is no hurry in discussions of this sort.

SOC. You are right in reminding me. For perhaps this is a good time to retrace our steps. For it is better to finish a little task well than a great deal imperfectly.

THEAET. Of course.

SOC. How, then, shall we set about it? What is it that we do say? Do we say that in every case of opinion there is a false opinion, and one of us has a false, and another a true opinion, because, as we believe, it is in the nature of things that this should be so?

THEAET. Yes, we do.

SOC. Then this, at any rate, is possible for us, is it not, regarding all things collectively and each thing separately, either to know or not to know them? For learning and forgetting, as intermediate stages, I leave out of account for the present, for just now they have no bearing upon our argument.

THEAET. Certainly, Socrates, nothing is left in any particular case except knowing or not knowing it.

SOC. Then he who forms opinion must form opinion either about what he knows or about what he does not know?

THEAET. Necessarily.

SOC. And it is surely impossible that one who knows a thing does not know it, or that one who does not know it knows it.

THEAET. Certainly.

SOC. Then does he who forms false opinions think that the things which he knows are not these things, but some others of the things he knows, and so, knowing both, is he ignorant of both?

THEAET. That is impossible, Socrates.

SOC. Well then, does he think that the things he does not know are other things which he does not know—which is as if a man who knows neither Theaetetus nor Socrates should conceive the idea that Socrates is Theaetetus or Theaetetus Socrates?

THEAET. That is impossible.

SOC. But surely a man does not think that the things he knows are the things he does not know, or again that the things he does not know are the things he knows.

THEAET. That would be a monstrous absurdity.

SOC. Then how could he still form false opinions? For inasmuch as all things are either known or unknown to us, it is impossible, I imagine, to form opinions outside of these alternatives, and within them it is clear that there is no place for fake opinion.

THEAET. Very true.

SOC. Had we, then, better look for what we are seeking, not by this method of knowing and not knowing, but by that of being and not being?

THEAET. What do you mean?

SOC. We may simply assert that he who on any subject holds opinions which are not, will certainly think falsely, no matter what the condition of his mind may be in other respects.

THEAET. That, again, is likely, Socrates.

SOC. Well then, what shall we say, Theaetetus, if anyone asks us, Is that which is assumed in common speech possible at all, and can any human being hold an opinion which is not, whether it be concerned with any of the things which are, or be entirely independent of them? We, I fancy, shall reply, Yes, when, in thinking, he thinks what is not true, shall we not?

THEAET. Yes.

SOC. And is the same sort of thing possible in any other field?

THEAET. What sort of thing?

SOC. For instance, that a man sees something, but sees nothing.

THEAET. How can he?

SOC. Yet surely if a man sees any one thing, he sees something that is. Or do you, perhaps, think one is among the things that are not?

THEAET. No, I do not.

SOC. Then he who sees any one thing, sees something that is.

THEAET. That is clear.

SOC. And therefore he who hears anything, hears some one thing and therefore hears what is.

THEAET. Yes.

SOC. And he who touches anything, touches some one thing, which is, since it is one?

THEAET. That also is true.

SOC. So, then, does not he who holds an opinion hold an opinion of some one thing?

THEAET. He must do so.

SOC. And does not he who holds an opinion of some one thing hold an opinion of something that is?

THEAET. I agree.

SOC. Then he who holds an opinion of what is not holds an opinion of nothing.

THEAET. Evidently.

SOC. Well then, he who holds an opinion of nothing, holds no opinion at all.

THEAET. That is plain, apparently.

SOC. Then it is impossible to hold an opinion of that which is not, either in relation to things that are, or independently of them.

THEAET. Evidently.

SOC. Then holding false opinion is something different from holding an opinion of that which is not?

THEAET. So it seems.

SOC. Then false opinion is not found to exist in us either by this method or by that which we followed a little while ago.

THEAET. No, it certainly is not.

SOC. But does not that which we call by that name arise after the following manner?

THEAET. After what manner?

SOC. We say that false opinion is a kind of interchanged opinion, when a person makes an exchange in his mind and says that one thing which exists is another thing which exists. For in this way he always holds an opinion of what exists, but of one thing instead of another; so he misses the object he was aiming at in his thought and might fairly be said to hold a false opinion.

THEAET. Now you seem to me to have said what is perfectly right. For when a man, in forming an opinion, puts ugly instead of beautiful, or beautiful instead of ugly, he does truly hold a false opinion.

SOC. Evidently, Theaetetus, you feel contempt of me, and not fear.

THEAET. Why in the world do you say that?

SOC. You think, I fancy, that I would not attack your truly false by asking whether it is possible for a thing to become slowly quick or heavily light, or any other opposite, by a process opposite to itself, in accordance, not with its own nature, but with that of its opposite. But I let this pass, that your courage may not fail. You are satisfied, you say, that false opinion is interchanged opinion?

THEAET. I am.

SOC. It is, then, in your opinion, possible for the mind to regard one thing as another and not as what it is.

THEAET. Yes, it is.

SOC. Now when one’s mind does this, does it not necessarily have a thought either of both things together or of one or the other of them?

THEAET. Yes, it must; either of both at the same time or in succession.

SOC. Excellent. And do you define thought as I do?

THEAET. How do you define it?

SOC. As the talk which the soul has with itself about any subjects which it considers. You must not suppose that I know this that I am declaring to you. But the soul, as the image presents itself to me, when it thinks, is merely conversing with itself, asking itself questions and answering, affirming and denying. When it has arrived at a decision, whether slowly or with a sudden bound, and is at last agreed, and is not in doubt, we call that its opinion; and so I define forming opinion as talking and opinion as talk which has been held, not with someone else, nor yet aloud, but in silence with oneself. How do you define it?

THEAET. In the same way.

SOC. Then whenever a man has an opinion that one thing is another, he says to himself, we believe, that the one thing is the other.

THEAET. Certainly.

SOC. Now call to mind whether you have ever said to yourself that the beautiful is most assuredly ugly, or the wrong right, or—and this is the sum of the whole matter—consider whether you have ever tried to persuade yourself that one thing is most assuredly another, or whether quite the contrary is the case, and you have never ventured, even in sleep, to say to yourself that the odd is, after all, certainly even, or anything of that sort.

THEAET. You are right.

SOC. Do you imagine that anyone else, sane or insane, ever ventured to say to himself seriously and try to persuade himself that the ox must necessarily be a horse, or two one?

THEAET. No, by Zeus, I do not.

SOC. Then if forming opinion is talking to oneself, no one who talks and forms opinion of two objects and apprehends them both with his soul, could say and have the opinion that one is the other. But you will also have to give up the expression one and other. This is what I mean, that nobody holds the opinion that the ugly is beautiful, or anything of that sort.

THEAET. Well, Socrates, I do give it up; and I agree with you in what you say.

SOC. You agree, therefore, that he who holds an opinion of both things cannot hold the opinion that one is the other.

THEAET. So it seems.

SOC. But surely he who holds an opinion of one only, and not of the other at all, will never hold the opinion that one is the other.

THEAET. You are right; for he would be forced to apprehend also that of which he holds no opinion.

SOC. Then neither he who holds opinion of both nor he who holds it of one can hold the opinion that a thing is something else. And so anyone who sets out to define false opinion as interchanged opinion would be talking nonsense. Then neither by this method nor by our previous methods is false opinion found to exist in us.

THEAET. Apparently not.

SOC. But yet, Theaetetus, if this is found not to exist, we shall be forced to admit many absurdities.

THEAET. What absurdities?

SOC. I will not tell you until I have tried to consider the matter in every way. For I should be ashamed of us, if, in our perplexity, we were forced to make such admissions as those to which I refer. But if we find the object of our quest, and are set free from perplexity, then, and not before, we will speak of others as involved in those absurdities, and we ourselves shall stand free from ridicule. But if we find no escape from our perplexity, we shall, I fancy, become low-spirited, like seasick people, and shall allow the argument to trample on us and do to us anything it pleases. Hear, then, by what means I still see a prospect of success for our quest.

THEAET. Do speak.

SOC. I shall deny that we were right when we agreed that it is impossible for a man to have opinion that the things he does not know are the things which he knows, and thus to be deceived. But there is a way in which it is possible.

THEAET. Do you mean what I myself suspected when we made the statement to which you refer, that sometimes I, though I know Socrates, saw at a distance someone whom I did not know, and thought it was Socrates whom I do know? In such a case false opinion does arise.

SOC. But did not we reject that, because it resulted in our knowing and not knowing the things which we know?

THEAET. Certainly we did.

SOC. Let us, then, not make that assumption, but another; perhaps it will turn out well for us, perhaps the opposite. But we are in such straits that we must turn every argument round and test it from all sides. Now see if this is sensible: Can a man who did not know a thing at one time learn it later?

THEAET. To be sure he can.

SOC. Again, then, can he learn one thing after another?

THEAET. Why not?

SOC. Please assume, then, for the sake of argument, that there is in our souls a block of wax, in one case larger, in another smaller, in one case the wax is purer, in another more impure and harder, in some cases softer, and in some of proper quality.

THEAET. I assume all that.

SOC. Let us, then, say that this is the gift of Memory, the mother of the Muses, and that whenever we wish to remember anything we see or hear or think of in our own minds, we hold this wax under the perceptions and thoughts and imprint them upon it, just as we make impressions from seal rings; and whatever is imprinted we remember and know as long as its image lasts, but whatever is rubbed out or cannot be imprinted we forget and do not know.

THEAET. Let us assume that.

SOC. Now take a man who knows the things which he sees and hears, and is considering some one of them; observe whether he may not gain a false opinion in the following manner.

THEAET. In what manner?

SOC. By thinking that the things which he knows are sometimes things which he knows and sometimes things which he does not know. For we were wrong before in agreeing that this is impossible.

THEAET. What do you say about it now?

SOC. We must begin our discussion of the matter by making the following distinctions: It is impossible for anyone to think that one thing which he knows and of which he has received a memorial imprint in his soul, but which he does not perceive, is another thing which he knows and of which also he has an imprint, and which he does not perceive. And, again, he cannot think that what he knows is that which he does not know and of which he has no seal; nor that what he does not know is another thing which he does not know; nor that what he does not know is what he knows; nor can he think that what he perceives is something else which he perceives; nor that what he perceives is something which he does not perceive; nor that what he does not perceive is something else which he does not perceive; nor that what he does not perceive is something which he perceives. And, again, it is still more impossible, if that can be, to think that a thing which he knows and perceives and of which he has an imprint which accords with the perception is another thing which he knows and perceives and of which he has an imprint which accords with the perception. And he cannot think that what he knows and perceives and of which he has a correct memorial imprint is another thing which he knows; nor that a thing which he knows and perceives and of which he has such an imprint is another thing which he perceives; nor again that a thing which he neither knows nor perceives is another thing which he neither knows nor perceives; nor that a thing which he neither knows nor perceives is another thing which he does not know; nor that a thing which he neither knows nor perceives is another thing which he does not perceive. In all these cases it is impossible beyond everything for false opinion to arise in the mind of anyone. The possibility that it may arise remains, if anywhere, in the following cases.

THEAET. What cases are they? I hope they may help me to understand better; for now I cannot follow you.

SOC. The cases in which he may think that things which he knows are some other things which he knows and perceives; or which he does not know, but perceives; or that things which he knows and perceives are other things which he knows and perceives.

THEAET. Now I am even more out of the running than before.

SOC. Then let me repeat it in a different way. I know Theodorus and remember within myself what sort of a person he is, and just so I know Theaetetus, but sometimes I see them, and sometimes I do not, sometimes I touch them, sometimes not, sometimes I hear them or perceive them through some other sense, and sometimes I have no perception of you at all, but I remember you none the less and know you in my own mind. Is it not so?

THEAET. Certainly.

SOC. This, then, is the first of the points which I wish to make clear. Note that one may perceive or not perceive that which one knows.

THEAET. That is true.

SOC. So, too, with that which he does not know—he may often not even perceive it, and often he may merely perceive it?

THEAET. That too is possible.

SOC. See if you follow me better now. If Socrates knows Theodorus and Theaetetus, but sees neither of them and has no other perception of them, he never could have the opinion within himself that Theaetetus is Theodorus. Am I right or wrong?

THEAET. You are right.

SOC. Now that was the first of the cases of which I spoke.

THEAET. Yes, it was.

SOC. The second is this: knowing one of you and not knowing the other, and not perceiving either of you, I never could think that the one whom I know is the one whom I do not know.

THEAET. Right.

SOC. And this is the third case: not knowing and not perceiving either of you, I could not think that he whom I do not know is someone else whom I do not know. And imagine that you have heard all the other cases again in succession, in which I could never form false opinions about you and Theodorus, either when I know or do not know both of you, or when I know one and not the other; and the same is true if we say perceive instead of know. Do you follow me?

THEAET. I follow you.

SOC. Then the possibility of forming false opinion remains in the following case: when, for example, knowing you and Theodorus, and having on that block of wax the imprint of both of you, as if you were signet-rings, but seeing you both at a distance and indistinctly, I hasten to assign the proper imprint of each of you to the proper vision, and to make it fit, as it were, its own footprint, with the purpose of causing recognition; [*](Aesch. Lib. 197 ff. makes Electra recognize the presence of her brother Orestes by the likeness of his footprints to her own.) but I may fail in this by interchanging them, and put the vision of one upon the imprint of the other, as people put a shoe on the wrong foot; or, again, I may be affected as the sight is affected when we use a mirror and the sight as it flows makes a change from right to left, and thus make a mistake; it is in such cases, then, that interchanged opinion occurs and the forming of false opinion arises.

THEAET. I think it does, Socrates. You describe what happens to opinion marvelously well.

SOC. There is still the further case, when, knowing both of you, I perceive one in addition to knowing him, but do not perceive the other, and the knowledge which I have of that other is not in accord with my perception. This is the case I described in this way before, and at that time you did not understand me.

THEAET. No, I did not.

SOC. This is what I meant, that if anyone knows and perceives one of you, and has knowledge of him which accords with the perception, he will never think that he is someone else whom he knows and perceives and his knowledge of whom accords with the perception. That was the case, was it not?

THEAET. Yes.

SOC. But we omitted, I believe, the case of which I am speaking now—the case in which we say the false opinion arises: when a man knows both and sees both (or has some other perception of them), but fails to hold the two imprints each under its proper perception; like a bad archer he shoots beside the mark and misses it; and it is just this which is called error or deception.

THEAET. And properly so.

SOC. Now when perception is present to one of the imprints but not to the other, and the mind applies the imprint of the absent perception to the perception which is present, the mind is deceived in every such instance. In a word, if our present view is sound, false opinion or deception seems to be impossible in relation to things which one does not know and has never perceived; but it is precisely in relation to things which we know and perceive that opinion turns and twists, becoming false and true—true when it puts the proper imprints and seals fairly and squarely upon one another, and false when it applies them sideways and aslant.

THEAET. Well, then, Socrates, is that view not a good one?

SOC. After you have heard the rest, you will be still more inclined to say so. For to hold a true opinion is a good thing, but to be deceived is a disgrace.

THEAET. Certainly.

SOC. They say the cause of these variations is as follows: When the wax in the soul of a man is deep and abundant and smooth and properly kneaded, the images that come through the perceptions are imprinted upon this heart of the soul—as Homer calls it in allusion to its similarity to wax [*](The similarity is in the Greek words κέαρ or κῆρ, heart, and κηρός, wax. The shaggy heart is mentioned in the Hom. Il. 2.851; Hom. Il. 16.554 The citation of Homer, here and below, is probably sarcastic—in reference to the practice of some of the sophists who used and perverted his words in support of their doctrines.)—; when this is the case, and in such men, the imprints, being clear and of sufficient depth, are also lasting. And men of this kind are in the first place quick to learn, and secondly they have retentive memories, and moreover they do not interchange the imprints of their perceptions, but they have true opinions. For the imprints are clear and have plenty of room, so that such men quickly assign them to their several moulds, which are called realities; and these men, then, are called wise. Or do you not agree?

THEAET. Most emphatically.

SOC. Now when the heart of anyone is shaggy (a condition which the all-wise poet commends), or when it is unclean or of impure wax, or very soft or hard, those whose wax is soft are quick to learn, but forgetful, and those in whom it is hard are the reverse. But those in whom it is shaggy and rough and stony, infected with earth or dung which is mixed in it, receive indistinct imprints from the moulds.

SO.So also do those whose wax is hard; for the imprints lack depth. And imprints in soft wax are also indistinct, because they melt together and quickly become blurred; but if besides all this they are crowded upon one another through lack of room, in some mean little soul, they are still more indistinct. So all these men are likely to have false opinions. For when they see or hear or think of anything, they cannot quickly assign things to the right imprints, but are slow about it, and because they assign them wrongly they usually see and hear and think amiss. These men, in turn, are accordingly said to be deceived about realities and ignorant.

THEAET. You are right as right could be, Socrates.

SOC. Shall we, then, say that false opinions exist in us?

THEAET. Assuredly.

SOC. And true opinions, no doubt?

THEAET. And true ones also.

SOC. Then now at last we think we have reached a valid agreement, that these two kinds of opinion incontestably exist?

THEAET. Most emphatically.

SOC. Truly, Theaetetus, a garrulous man is a strange and unpleasant creature!

THEAET. Eh? What makes you say that?

SOC. Vexation at my own stupidity and genuine garrulity. For what else could you call it when a man drags his arguments up and down because he is so stupid that he cannot be convinced, and is hardly to be induced to give up any one of them?

THEAET. But you, why are you vexed?

SOC. I am not merely vexed, I am actually afraid; for I do not know what answer to make if anyone asks me: Socrates, have you found out, I wonder, that false opinion exists neither in the relations of the perceptions to one another nor in the thoughts, but in the combination of perception with thought? I shall say yes, I suppose, and put on airs, as if we had made a fine discovery.

THEAET. It seems to me, Socrates, that the result we have now brought out is not half bad.

SOC.Do you go on and assert, then, he will say, that we never could imagine that the man whom we merely think of, but do not see, is a horse which also we do not see or touch or perceive by any other sense, but merely think of? I suppose I shall say that I do make that assertion.

THEAET. Yes, and you will be right.

SOC.Then, he will say, according to that, could we ever imagine that the number eleven which is merely thought of, is the number twelve which also is merely thought of? Come now, it is for you to answer.

THEAET. Well, my answer will be that a man might imagine the eleven that he sees or touches to be twelve, but that he could never have that opinion concerning the eleven that he has in his mind.

SOC. Well, then, do you think that anyone ever considered in his own mind five and seven,— I do not mean by setting before his eyes seven men and five men and considering them, or anything of that sort, but seven and five in the abstract, which we say are imprints in the block of wax, and in regard to which we deny the possibility of forming false opinions—taking these by themselves, do you imagine that anybody in the world has ever considered them, talking to himself and asking himself what their sum is, and that one person has said and thought eleven, and another twelve, or do all say and think that it is twelve?

THEAET. No, by Zeus; many say eleven, and if you take a larger number for consideration, there is greater likelihood of error. For I suppose you are speaking of any number rather than of these only.

SOC. You are right in supposing so; and consider whether in that instance the abstract twelve in the block of wax is not itself imagined to be eleven.

THEAET. It seems so.

SOC. Have we not, then, come back again to the beginning of our talk? For the man who is affected in this way imagines that one thing which he knows is another thing which he knows. This we said was impossible, and by this very argument we were forcing false opinion out of existence, that the same man might not be forced to know and not know the same things at the same time.

THEAET. Very true.

SOC. Then we must show that forming false opinion is something or other different from the interchange of thought and perception. For if it were that, we should never be deceived in abstract thoughts. But as the case now stands, either there is no false opinion or it is possible for a man not to know that which he knows. Which alternative will you choose?

THEAET. There is no possible choice, Socrates.

SOC. And yet the argument is not likely to admit both. But still, since we must not shrink from any risk, what if we should try to do a shameless deed?

THEAET. What is it?

SOC. To undertake to tell what it really is to know.

THEAET. And why is that shameless?

SOC. You seem not to remember that our whole talk from the beginning has been a search for knowledge, because we did not know what it is.

THEAET. Oh yes, I remember.

SOC. Then is it not shameless to proclaim what it is to know, when we are ignorant of knowledge? But really, Theaetetus, our talk has been badly tainted with unclearness all along; for we have said over and over again we know and we do not know and we have knowledge and we have no knowledge, as if we could understand each other, while we were still ignorant of knowledge; and at this very moment, if you please, we have again used the terms be ignorant and understand, as though we had any right to use them if we are deprived of knowledge.

THEAET. But how will you converse, Socrates, if you refrain from these words?

SOC. Not at all, being the man I am; but I might if I were a real reasoner; if such a man were present at this moment he would tell us to refrain from these terms, and would criticize my talk scathingly. But since we are poor creatures, shall I venture to say what the nature of knowing is? For it seems to me that would be of some advantage.

THEAET. Venture it then, by Zeus. You shall have full pardon for not refraining from those terms.

SOC. Have you heard what they say nowadays that knowing is?

THEAET. Perhaps; however, I don’t remember just at this moment.

SOC. They say it is having knowledge.

THEAET. True.

SOC. Let us make a slight change and say possessing knowledge.

THEAET. Why, how will you claim that the one differs from the other?

SOC. Perhaps it doesn’t; but first hear how it seems to me to differ, and then help me to test my view.

THEAET. I will if I can.

SOC. Well, then, having does not seem to me the same as possessing. For instance, if a man bought a cloak and had it under his control, but did not wear it, we should certainly say, not that he had it, but that he possessed it.

THEAET. And rightly.

SOC. Now see whether it is possible in the same way for one who possesses knowledge not to have it, as, for instance, if a man should catch wild birds—pigeons or the like—and should arrange an aviary at home and keep them in it, we might in a way assert that he always has them because he possesses them, might we not?

THEAET. Yes.

SOC. And yet in another way that he has none of them, but that he has acquired power over them, since he has brought them under his control in his own enclosure, to take them and hold them whenever he likes, by catching whichever bird he pleases, and to let them go again; and he can do this as often as be sees fit.

THEAET. That is true.

SOC. Once more, then, just as a while ago we contrived some sort of a waxen figment in the soul, so now let us make in each soul an aviary stocked with all sorts of birds, some in flocks apart from the rest, others in small groups, and some solitary, flying hither and thither among them all.

THEAET. Consider it done. What next?

SOC. We must assume that while we are children this receptacle is empty, and we must understand that the birds represent the varieties of knowledge. And whatsoever kind of knowledge a person acquires and shuts up in the enclosure, we must say that he has learned or discovered the thing of which this is the knowledge, and that just this is knowing.

THEAET. So be it.

SOC. Consider then what expressions are needed for the process of recapturing and taking and holding and letting go again whichever he please of the kinds of knowledge, whether they are the same expressions as those needed for the original acquisition, or others. But you will understand better by an illustration. You admit that there is an art of arithmetic?

THEAET. Yes.

SOC. Now suppose this to be a hunt after the kinds of knowledge, or sciences, of all odd and even numbers.

THEAET. I do so.

SOC. Now it is by this art, I imagine, that a man has the sciences of numbers under his own control and also that any man who transmits them to another does this.

THEAET. Yes.

SOC. And we say that when anyone transmits them he teaches, and when anyone receives them he learns, and when anyone, by having acquired them, has them in that aviary of ours, he knows them.

THEAET. Certainly.

SOC. Now pay attention to what follows from this. Does not the perfect arithmetician understand all numbers; for he has the sciences of all numbers in his mind?

THEAET. To be sure.

SOC. Then would such a man ever count anything—either any abstract numbers in his head, or any such external objects as possess number?

THEAET. Of course,

SOC. But we shall affirm that counting is the same thing as considering how great any number in question is.

THEAET. We shall.

SOC. Then he who by our previous admission knows all number is found to be considering that which he knows as if he did not know it. You have doubtless heard of such ambiguities.

THEAET. Yes, I have.

SOC. Continuing, then, our comparison with the acquisition and hunting of the pigeons, we shall say that the hunting is of two kinds, one before the acquisition for the sake of possessing, the other carried on by the possessor for the sake of taking and holding in his hands what he had acquired long before. And just so when a man long since by learning came to possess knowledge of certain things, and knew them, he may have these very things afresh by taking up again the knowledge of each of them separately and holding it—the knowledge which he had acquired long before, but had not at hand in his mind?

THEAET. That is true.

SOC. This, then, was my question just now: How should we express ourselves in speaking about them when an arithmetician undertakes to count or a man of letters to read something? In such a case shall we say that although he knows he sets himself to learn again from himself that which he knows?

THEAET. But that is extraordinary, Socrates.

SOC. But shall we say that he is going to read or count that which he does not know, when we have granted that he knows all letters and all numbers?

THEAET. But that too is absurd.

SOC. Shall we then say that words are nothing to us, if it amuses anyone to drag the expressions know and learn one way and another, but since we set up the distinction that it is one thing to possess knowledge and another thing to have it, we affirm that it is impossible not to possess what one possesses, so that it never happens that a man does not know that which he knows, but that it is possible to conceive a false opinion about it? For it is possible to have not the knowledge of this thing, but some other knowledge instead, when in hunting for some one kind of knowledge, as the various kinds fly about, he makes a mistake and catches one instead of another; so in one example he thought eleven was twelve, because he caught the knowledge of twelve, which was within him, instead of that of eleven, caught a ringdove, as it were, instead of a pigeon.

THEAET. Yes, that is reasonable.

SOC. But when he catches the knowledge he intends to catch, he is not deceived and has true opinion, and so true and false opinion exist and none of the things which formerly annoyed us interferes? Perhaps you will agree to this; or what will you do?

THEAET. I will agree.

SOC. Yes, for we have got rid of our difficulty about men not knowing that which they know; for we no longer find ourselves not possessing that which we possess, whether we are deceived about anything or not. However, another more dreadful disaster seems to be coming in sight.

THEAET. What disaster?

SOC. If the interchange of kinds of knowledge should ever turn out to be false opinion.

THEAET. How so?

SOC. Is it not the height of absurdity, in the first place for one who has knowledge of something to be ignorant of this very thing, not through ignorance but through his knowledge; secondly, for him to be of opinion that this thing is something else and something else is this thing—for the soul, when knowledge has come to it, to know nothing and be ignorant of all things? For by this argument there is nothing to prevent ignorance from coming to us and making us know something and blindness from making us see, if knowledge is ever to make us ignorant.

THEAET. Perhaps, Socrates, we were not right in making the birds represent kinds of knowledge only, but we ought to have imagined kinds of ignorance also flying about in the soul with the others; then the hunter would catch sometimes knowledge and sometimes ignorance of the same thing, and through the ignorance he would have false, but through the knowledge true opinion.

SOC. It is not easy, Theaetetus, to refrain from praising you. However, examine your suggestion once more. Let it be as you say: the man who catches the ignorance will, you say, have false opinion. Is that it?

THEAET. Yes.

SOC. But surely he will not also think that he has false opinion.

THEAET. Certainly not.

SOC. No, but true opinion, and will have the attitude of knowing that about which he is deceived.

THEAET. Of course.

SOC. Hence he will fancy that he has caught, and has, knowledge, not ignorance.

THEAET. Evidently.

SOC. Then, after our long wanderings, we have come round again to our first difficulty. For the real reasoner will laugh and say, Most excellent Sirs, does a man who knows both knowledge and ignorance think that one of them, which he knows, is another thing which he knows; or, knowing neither of them, is he of opinion that one, which he does not know, is another thing which he does not know; or, knowing one and not the other, does he think that the one he does not know is the one he knows; or that the one he knows is the one he does not know? Or will you go on and tell me that there are kinds of knowledge of the kinds of knowledge and of ignorance, and that he who possesses these kinds of knowledge and has enclosed them in some sort of other ridiculous aviaries or waxen figments, knows them, so long as he possesses them, even if he has them not at hand in his soul? And in this fashion are you going to be compelled to trot about endlessly in the same circle without making any progress? What shall we reply to this, Theaetetus?

THEAET. By Zeus, Socrates, I don’t know what to say.

SOC. Then, my boy, is the argument right in rebuking us and in pointing out that we were wrong to abandon knowledge and seek first for false opinion? It is impossible to know the latter until we have adequately comprehended the nature of knowledge.

THEAET. As the case now stands, Socrates, we cannot help thinking as you say.

SOC. To begin, then, at the beginning once more, what shall we say knowledge is? For surely we are not going to give it up yet, are we?

THEAET. Not by any means, unless, that is, you give it up.

SOC. Tell us, then, what definition will make us contradict ourselves least.

THEAET. The one we tried before, Socrates; at any rate, I have nothing else to offer.

SOC. What one?

THEAET. That knowledge is true opinion; for true opinion is surely free from error and all its results are fine and good.

SOC. The man who was leading the way through the river, [*](A man who was leading the way through a river was asked if the water was deep. He replied αὐτὸ δείξει, the event itself will show (i.e. you can find out by trying). The expression became proverbial.) Theaetetus, said: The result itself will show; and so in this matter, if we go on with our search, perhaps the thing will turn up in our path and of itself reveal the object of our search; but if we stay still, we shall discover nothing.

THEAET. You are right; let us go on with our investigation.

SOC. Well, then, this at least calls for slight investigation; for you have a whole profession which declares that true opinion is not knowledge.

THEAET. How so? What profession is it?

SOC. The profession of those who are greatest in wisdom, who are called orators and lawyers; for they persuade men by the art which they possess, not teaching them, but making them have whatever opinion they like. Or do you think there are any teachers so clever as to be able, in the short time allowed by the water-clock, [*](The length of speeches in the Athenian law courts was limited by a water-clock.) satisfactorily to teach the judges the truth about what happened to people who have been robbed of their money or have suffered other acts of violence, when there were no eyewitnesses?

THEAET. I certainly do not think so; but I think they can persuade them.

SOC. And persuading them is making them have an opinion, is it not?

THEAET. Of course.

SOC. Then when judges are justly persuaded about matters which one can know only by having seen them and in no other way, in such a case, judging of them from hearsay, having acquired a true opinion of them, they have judged without knowledge, though they are rightly persuaded, if the judgement they have passed is correct, have they not?

THEAET. Certainly.

SOC. But, my friend, if true opinion and knowledge were the same thing in law courts, the best of judges could never have true opinion without knowledge; in fact, however, it appears that the two are different.

THEAET. Oh yes, I remember now, Socrates, having heard someone make the distinction, but I had forgotten it. He said that knowledge was true opinion accompanied by reason, but that unreasoning true opinion was outside of the sphere of knowledge; and matters of which there is not a rational explanation are unknowable—yes, that is what he called them—and those of which there is are knowable.

SOC. I am glad you mentioned that. But tell us how he distinguished between the knowable and the unknowable, that we may see whether the accounts that you and I have heard agree.

THEAET. But I do not know whether I can think it out; but if someone else were to make the statement of it, I think I could follow.

SOC. Listen then, while I relate it to you—a dream for a dream. I in turn used to imagine that I heard certain persons say that the primary elements of which we and all else are composed admit of no rational explanation;