Socrates 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, 190a 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?

Theaetetus THEAET. In the same way.

Socrates 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.

Theaetetus THEAET. Certainly.

Socrates 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.

Theaetetus THEAET. You are right.

Socrates 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?

Theaetetus THEAET. No, by Zeus, I do not.

Socrates 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 190d anything of that sort.

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

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

Theaetetus THEAET. So it seems.

Socrates 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.

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

Socrates 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. 190e 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.

Theaetetus THEAET. Apparently not.

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

Theaetetus THEAET. What absurdities?

Socrates 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, 191a 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.

Theaetetus THEAET. Do speak.

Socrates 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, 191b and thus to be deceived. But there is a way in which it is possible.

Theaetetus 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.

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

Theaetetus THEAET. Certainly we did.

Socrates SOC. Let us, then, not make that assumption, but another; perhaps 191c 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?

Theaetetus THEAET. To be sure he can.

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

Theaetetus THEAET. Why not?

Socrates 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, 191d and in some of proper quality.

Theaetetus THEAET. I assume all that.

Socrates 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 191e cannot be imprinted we forget and do not know.

Theaetetus THEAET. Let us assume that.

Socrates 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.

Theaetetus THEAET. In what manner?

Socrates 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.

Theaetetus THEAET. What do you say about it now?

Socrates 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 192b 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; 192c 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.

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

Socrates 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 192d he knows and perceives.

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

Socrates 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?

Theaetetus THEAET. Certainly.

Socrates 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.

Theaetetus THEAET. That is true.

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

Theaetetus THEAET. That too is possible.