Socrates 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.

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

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

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

Socrates SOC. They say it is having knowledge.

Theaetetus THEAET. True.

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

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

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

Theaetetus THEAET. I will if I can.

Socrates 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.

Theaetetus THEAET. And rightly.

Socrates 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?

Theaetetus THEAET. Yes.

Socrates 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, 197d 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.

Theaetetus THEAET. That is true.

Socrates 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.

Theaetetus THEAET. Consider it done. What next?

Socrates 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.

Theaetetus THEAET. So be it.

Socrates 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?

Theaetetus THEAET. Yes.

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

Theaetetus THEAET. I do so.

Socrates SOC. Now it is by this art, I imagine, that a man has 198b the sciences of numbers under his own control and also that any man who transmits them to another does this.

Theaetetus THEAET. Yes.

Socrates 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.

Theaetetus THEAET. Certainly.

Socrates 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?

Theaetetus THEAET. To be sure.

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

Theaetetus THEAET. Of course,

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

Theaetetus THEAET. We shall.

Socrates 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.

Theaetetus THEAET. Yes, I have.

Socrates SOC. Continuing, then, our comparison with the acquisition 198d 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?

Theaetetus THEAET. That is true.

Socrates 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?

Theaetetus THEAET. But that is extraordinary, Socrates.

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?

Theaetetus THEAET. But that too is absurd.

Socrates 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? 199b 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.

Theaetetus THEAET. Yes, that is reasonable.

Socrates 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 199c which formerly annoyed us interferes? Perhaps you will agree to this; or what will you do?

Theaetetus THEAET. I will agree.

Socrates 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.

Theaetetus THEAET. What disaster?

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

Theaetetus THEAET. How so?

Socrates 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.

Theaetetus 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.

Socrates SOC. It is not easy, Theaetetus, to refrain from praising you. However, examine your suggestion once more. Let it be as you say: 200a the man who catches the ignorance will, you say, have false opinion. Is that it?

Theaetetus THEAET. Yes.

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

Theaetetus THEAET. Certainly not.

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

Theaetetus THEAET. Of course.

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

Theaetetus THEAET. Evidently.

Socrates SOC. Then, after our long wanderings, we have come round again to our first difficulty. For the real reasoner 200b 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 200c 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?

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

Socrates 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? 200d It is impossible to know the latter until we have adequately comprehended the nature of knowledge.

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

Socrates 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?

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

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

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

Socrates SOC. What one?

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