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;