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?