Theaetetus

SOCRATES: How there can be false opinion - that difficulty still troubles the eye of my mind; and I am uncertain whether I shall leave the question, or begin over again in a new way. THEAETETUS: Begin again, Socrates, - at least if you think that there is the slightest necessity for doing so. Were not you and Theodorus just now remarking very truly, that in discussions of this kind we may take our own time? SOCRATES: You are quite right, and perhaps there will be no harm in retracing our steps and beginning again. Better a little which is well done, than a great deal imperfectly. THEAETETUS: Certainly. SOCRATES: Well, and what is the difficulty? Do we not speak of false opinion, and say that one man holds a false and another a true opinion, as though there were some natural distinction between them? THEAETETUS: We certainly say so. SOCRATES: All things and everything are either known or not known. I leave out of view the intermediate conceptions of learning and forgetting, because they have nothing to do with our present question. THEAETETUS: There can be no doubt, Socrates, if you exclude these, that there is no other alternative but knowing or not knowing a thing.

SOCRATES: That point being now determined, must we not say that he who has an opinion, must have an opinion about something which he knows or does not know? THEAETETUS: He must. SOCRATES: He who knows, cannot but know; and he who does not know, cannot know? THEAETETUS: Of course. SOCRATES: What shall we say then? When a man has a false opinion does he think that which he knows to be some other thing which he knows, and knowing both, is he at the same time ignorant of both? THEAETETUS: That, Socrates, is impossible. SOCRATES: But perhaps he thinks of something which he does not know as some other thing which he does not know; for example, he knows neither Theaetetus nor Socrates, and yet he fancies that Theaetetus is Socrates, or Socrates Theaetetus? THEAETETUS: How can he? SOCRATES: But surely he cannot suppose what he knows to be what he does not know, or what he does not know to be what he knows? THEAETETUS: That would be monstrous. SOCRATES: Where, then, is false opinion? For if all things are either known or unknown, there can be no opinion which is not comprehended under this alternative, and so false opinion is excluded. THEAETETUS: Most true.

SOCRATES: Suppose that we remove the question out of the sphere of knowing or not knowing, into that of being and not-being. THEAETETUS: What do you mean? SOCRATES: May we not suspect the simple truth to be that he who thinks about anything, that which is not, will necessarily think what is false, whatever in other respects may be the state of his mind? THEAETETUS: That, again, is not unlikely, Socrates. SOCRATES: Then suppose some one to say to us, Theaetetus: - Is it possible for any man to think that which is not, either as a self-existent substance or as a predicate of something else? And suppose that we answer, 'Yes, he can, when he thinks what is not true.' - That will be our answer? THEAETETUS: Yes. SOCRATES: But is there any parallel to this? THEAETETUS: What do you mean? SOCRATES: Can a man see something and yet see nothing? THEAETETUS: Impossible. SOCRATES: But if he sees any one thing, he sees something that exists. Do you suppose that what is one is ever to be found among non-existing things? THEAETETUS: I do not. SOCRATES: He then who sees some one thing, sees something which is? THEAETETUS: Clearly. SOCRATES: And he who hears anything, hears some one thing, and hears that which is? THEAETETUS: Yes.

SOCRATES: And he who touches anything, touches something which is one and therefore is? THEAETETUS: That again is true. SOCRATES: And does not he who thinks, think some one thing? THEAETETUS: Certainly. SOCRATES: And does not he who thinks some one thing, think something which is? THEAETETUS: I agree. SOCRATES: Then he who thinks of that which is not, thinks of nothing? THEAETETUS: Clearly. SOCRATES: And he who thinks of nothing, does not think at all? THEAETETUS: Obviously. SOCRATES: Then no one can think that which is not, either as a self-existent substance or as a predicate of something else? THEAETETUS: Clearly not. SOCRATES: Then to think falsely is different from thinking that which is not? THEAETETUS: It would seem so. SOCRATES: Then false opinion has no existence in us, either in the sphere of being or of knowledge? THEAETETUS: Certainly not. SOCRATES: But may not the following be the description of what we express by this name? THEAETETUS: What?

SOCRATES: May we not suppose that false opinion or thought is a sort of heterodoxy; a person may make an exchange in his mind, and say that one real object is another real object. For thus he always thinks that which is, but he puts one thing in place of another; and missing the aim of his thoughts, he may be truly said to have false opinion. THEAETETUS: Now you appear to me to have spoken the exact truth: when a man puts the base in the place of the noble, or the noble in the place of the base, then he has truly false opinion. SOCRATES: I see, Theaetetus, that your fear has disappeared, and that you are beginning to despise me. THEAETETUS: What makes you say so? SOCRATES: You think, if I am not mistaken, that your 'truly false' is safe from censure, and that I shall never ask whether there can be a swift which is slow, or a heavy which is light, or any other self-contradictory thing, which works, not according to its own nature, but according to that of its opposite. But I will not insist upon this, for I do not wish needlessly to discourage you. And so you are satisfied that false opinion is heterodoxy, or the thought of something else?

THEAETETUS: I am. SOCRATES: It is possible then upon your view for the mind to conceive of one thing as another? THEAETETUS: True. SOCRATES: But must not the mind, or thinking power, which misplaces them, have a conception either of both objects or of one of them? THEAETETUS: Certainly. SOCRATES: Either together or in succession? THEAETETUS: Very good. SOCRATES: And do you mean by conceiving, the same which I mean? THEAETETUS: What is that? SOCRATES: I mean the conversation which the soul holds with herself in considering of anything. I speak of what I scarcely understand; but the soul when thinking appears to me to be just talking - asking questions of herself and answering them, affirming and denying. And when she has arrived at a decision, either gradually or by a sudden impulse, and has at last agreed, and does not doubt, this is called her opinion. I say, then, that to form an opinion is to speak, and opinion is a word spoken, - I mean, to oneself and in silence, not aloud or to another: What think you? THEAETETUS: I agree. SOCRATES: Then when any one thinks of one thing as another, he is saying to himself that one thing is another? THEAETETUS: Yes.

SOCRATES: But do you ever remember saying to yourself that the noble is certainly base, or the unjust just; or, best of all - have you ever attempted to convince yourself that one thing is another? Nay, not even in sleep, did you ever venture to say to yourself that odd is even, or anything of the kind? THEAETETUS: Never. SOCRATES: And do you suppose that any other man, either in his senses or out of them, ever seriously tried to persuade himself that an ox is a horse, or that two are one? THEAETETUS: Certainly not. SOCRATES: But if thinking is talking to oneself, no one speaking and thinking of two objects, and apprehending them both in his soul, will say and think that the one is the other of them, and I must add, that even you, lover of dispute as you are, had better let the word 'other' alone (i.e. not insist that 'one' and 'other' are the same (Both words in Greek are called eteron: compare Parmen.; Euthyd.)). I mean to say, that no one thinks the noble to be base, or anything of the kind. THEAETETUS: I will give up the word 'other,' Socrates; and I agree to what you say.

SOCRATES: If a man has both of them in his thoughts, he cannot think that the one of them is the other? THEAETETUS: True. SOCRATES: Neither, if he has one of them only in his mind and not the other, can he think that one is the other? THEAETETUS: True; for we should have to suppose that he apprehends that which is not in his thoughts at all. SOCRATES: Then no one who has either both or only one of the two objects in his mind can think that the one is the other. And therefore, he who maintains that false opinion is heterodoxy is talking nonsense; for neither in this, any more than in the previous way, can false opinion exist in us. THEAETETUS: No. SOCRATES: But if, Theaetetus, this is not admitted, we shall be driven into many absurdities. THEAETETUS: What are they?

SOCRATES: I will not tell you until I have endeavoured to consider the matter from every point of view. For I should be ashamed of us if we were driven in our perplexity to admit the absurd consequences of which I speak. But if we find the solution, and get away from them, we may regard them only as the difficulties of others, and the ridicule will not attach to us. On the other hand, if we utterly fail, I suppose that we must be humble, and allow the argument to trample us under foot, as the sea-sick passenger is trampled upon by the sailor, and to do anything to us. Listen, then, while I tell you how I hope to find a way out of our difficulty. THEAETETUS: Let me hear. SOCRATES: I think that we were wrong in denying that a man could think what he knew to be what he did not know; and that there is a way in which such a deception is possible. THEAETETUS: You mean to say, as I suspected at the time, that I may know Socrates, and at a distance see some one who is unknown to me, and whom I mistake for him - then the deception will occur?

SOCRATES: But has not that position been relinquished by us, because involving the absurdity that we should know and not know the things which we know? THEAETETUS: True. SOCRATES: Let us make the assertion in another form, which may or may not have a favourable issue; but as we are in a great strait, every argument should be turned over and tested. Tell me, then, whether I am right in saying that you may learn a thing which at one time you did not know? THEAETETUS: Certainly you may. SOCRATES: And another and another? THEAETETUS: Yes. SOCRATES: I would have you imagine, then, that there exists in the mind of man a block of wax, which is of different sizes in different men; harder, moister, and having more or less of purity in one than another, and in some of an intermediate quality. THEAETETUS: I see.

SOCRATES: Let us say that this tablet is a gift of Memory, the mother of the Muses; and that when we wish to remember anything which we have seen, or heard, or thought in our own minds, we hold the wax to the perceptions and thoughts, and in that material receive the impression of them as from the seal of a ring; and that we remember and know what is imprinted as long as the image lasts; but when the image is effaced, or cannot be taken, then we forget and do not know. THEAETETUS: Very good. SOCRATES: Now, when a person has this knowledge, and is considering something which he sees or hears, may not false opinion arise in the following manner? THEAETETUS: In what manner? SOCRATES: When he thinks what he knows, sometimes to be what he knows, and sometimes to be what he does not know. We were wrong before in denying the possibility of this. THEAETETUS: And how would you amend the former statement?

SOCRATES: I should begin by making a list of the impossible cases which must be excluded. (1) No one can think one thing to be another when he does not perceive either of them, but has the memorial or seal of both of them in his mind; nor can any mistaking of one thing for another occur, when he only knows one, and does not know, and has no impression of the other; nor can he think that one thing which he does not know is another thing which he does not know, or that what he does not know is what he knows; nor (2) that one thing which he perceives is another thing which he perceives, or that something which he perceives is something which he does not perceive; or that something which he does not perceive is something else which he does not perceive; or that something which he does not perceive is something which he perceives; nor again (3) can he think that something which he knows and perceives, and of which he has the impression coinciding with sense, is something else which he knows and perceives, and of which he has the impression coinciding with sense; - this last case, if possible, is still more inconceivable than the others; nor (4) can he think that something which he knows and perceives, and of which he has the memorial coinciding with sense, is something else which he knows;

nor so long as these agree, can he think that a thing which he knows and perceives is another thing which he perceives; or that a thing which he does not know and does not perceive, is the same as another thing which he does not know and does not perceive; - nor again, can he suppose that a thing which he does not know and does not perceive is the same as another thing which he does not know; or that a thing which he does not know and does not perceive is another thing which he does not perceive: - All these utterly and absolutely exclude the possibility of false opinion. The only cases, if any, which remain, are the following.

SOCRATES: See whether you can follow me better now: Socrates can recognize Theodorus and Theaetetus, but he sees neither of them, nor does he perceive them in any other way; he cannot then by any possibility imagine in his own mind that Theaetetus is Theodorus. Am I not right? THEAETETUS: You are quite right. SOCRATES: Then that was the first case of which I spoke. THEAETETUS: Yes. SOCRATES: The second case was, that I, knowing one of you and not knowing the other, and perceiving neither, can never think him whom I know to be him whom I do not know. THEAETETUS: True. SOCRATES: In the third case, not knowing and not perceiving either of you, I cannot think that one of you whom I do not know is the other whom I do not know. I need not again go over the catalogue of excluded cases, in which I cannot form a false opinion about you and Theodorus, either when I know both or when I am in ignorance of both, or when I know one and not the other. And the same of perceiving: do you understand me? THEAETETUS: I do.

SOCRATES: I meant to say, that when a person knows and perceives one of you, his knowledge coincides with his perception, he will never think him to be some other person, whom he knows and perceives, and the knowledge of whom coincides with his perception - for that also was a case supposed. THEAETETUS: True. SOCRATES: But there was an omission of the further case, in which, as we now say, false opinion may arise, when knowing both, and seeing, or having some other sensible perception of both, I fail in holding the seal over against the corresponding sensation; like a bad archer, I miss and fall wide of the mark - and this is called falsehood. THEAETETUS: Yes; it is rightly so called.

SOCRATES: When, therefore, perception is present to one of the seals or impressions but not to the other, and the mind fits the seal of the absent perception on the one which is present, in any case of this sort the mind is deceived; in a word, if our view is sound, there can be no error or deception about things which a man does not know and has never perceived, but only in things which are known and perceived; in these alone opinion turns and twists about, and becomes alternately true and false; - true when the seals and impressions of sense meet straight and opposite - false when they go awry and crooked. THEAETETUS: And is not that, Socrates, nobly said? SOCRATES: Nobly! yes; but wait a little and hear the explanation, and then you will say so with more reason; for to think truly is noble and to be deceived is base. THEAETETUS: Undoubtedly.

SOCRATES: And the origin of truth and error is as follows: - When the wax in the soul of any one is deep and abundant, and smooth and perfectly tempered, then the impressions which pass through the senses and sink into the heart of the soul, as Homer says in a parable, meaning to indicate the likeness of the soul to wax (Kerh Kerhos); these, I say, being pure and clear, and having a sufficient depth of wax, are also lasting, and minds, such as these, easily learn and easily retain, and are not liable to confusion, but have true thoughts, for they have plenty of room, and having clear impressions of things, as we term them, quickly distribute them into their proper places on the block. And such men are called wise. Do you agree? THEAETETUS: Entirely.

SOCRATES: But when the heart of any one is shaggy - a quality which the all-wise poet commends, or muddy and of impure wax, or very soft, or very hard, then there is a corresponding defect in the mind - the soft are good at learning, but apt to forget; and the hard are the reverse; the shaggy and rugged and gritty, or those who have an admixture of earth or dung in their composition, have the impressions indistinct, as also the hard, for there is no depth in them; and the soft too are indistinct, for their impressions are easily confused and effaced. Yet greater is the indistinctness when they are all jostled together in a little soul, which has no room. These are the natures which have false opinion; for when they see or hear or think of anything, they are slow in assigning the right objects to the right impressions - in their stupidity they confuse them, and are apt to see and hear and think amiss - and such men are said to be deceived in their knowledge of objects, and ignorant. THEAETETUS: No man, Socrates, can say anything truer than that. SOCRATES: Then now we may admit the existence of false opinion in us? THEAETETUS: Certainly. SOCRATES: And of true opinion also? THEAETETUS: Yes.

SOCRATES: We have at length satisfactorily proven beyond a doubt there are these two sorts of opinion? THEAETETUS: Undoubtedly. SOCRATES: Alas, Theaetetus, what a tiresome creature is a man who is fond of talking! THEAETETUS: What makes you say so? SOCRATES: Because I am disheartened at my own stupidity and tiresome garrulity; for what other term will describe the habit of a man who is always arguing on all sides of a question; whose dulness cannot be convinced, and who will never leave off? THEAETETUS: But what puts you out of heart? SOCRATES: I am not only out of heart, but in positive despair; for I do not know what to answer if any one were to ask me: - O Socrates, have you indeed discovered that false opinion arises neither in the comparison of perceptions with one another nor yet in thought, but in union of thought and perception? Yes, I shall say, with the complacence of one who thinks that he has made a noble discovery. THEAETETUS: I see no reason why we should be ashamed of our demonstration, Socrates.

SOCRATES: He will say: You mean to argue that the man whom we only think of and do not see, cannot be confused with the horse which we do not see or touch, but only think of and do not perceive? That I believe to be my meaning, I shall reply. THEAETETUS: Quite right. SOCRATES: Well, then, he will say, according to that argument, the number eleven, which is only thought, can never be mistaken for twelve, which is only thought: How would you answer him? THEAETETUS: I should say that a mistake may very likely arise between the eleven or twelve which are seen or handled, but that no similar mistake can arise between the eleven and twelve which are in the mind. SOCRATES: Well, but do you think that no one ever put before his own mind five and seven, - I do not mean five or seven men or horses, but five or seven in the abstract, which, as we say, are recorded on the waxen block, and in which false opinion is held to be impossible; did no man ever ask himself how many these numbers make when added together, and answer that they are eleven, while another thinks that they are twelve, or would all agree in thinking and saying that they are twelve?

THEAETETUS: Certainly not; many would think that they are eleven, and in the higher numbers the chance of error is greater still; for I assume you to be speaking of numbers in general. SOCRATES: Exactly; and I want you to consider whether this does not imply that the twelve in the waxen block are supposed to be eleven? THEAETETUS: Yes, that seems to be the case. SOCRATES: Then do we not come back to the old difficulty? For he who makes such a mistake does think one thing which he knows to be another thing which he knows; but this, as we said, was impossible, and afforded an irresistible proof of the non-existence of false opinion, because otherwise the same person would inevitably know and not know the same thing at the same time. THEAETETUS: Most true. SOCRATES: Then false opinion cannot be explained as a confusion of thought and sense, for in that case we could not have been mistaken about pure conceptions of thought; and thus we are obliged to say, either that false opinion does not exist, or that a man may not know that which he knows; - which alternative do you prefer? THEAETETUS: It is hard to determine, Socrates.

SOCRATES: And yet the argument will scarcely admit of both. But, as we are at our wits' end, suppose that we do a shameless thing? THEAETETUS: What is it? SOCRATES: Let us attempt to explain the verb 'to know.' THEAETETUS: And why should that be shameless? SOCRATES: You seem not to be aware that the whole of our discussion from the very beginning has been a search after knowledge, of which we are assumed not to know the nature. THEAETETUS: Nay, but I am well aware. SOCRATES: And is it not shameless when we do not know what knowledge is, to be explaining the verb 'to know'? The truth is, Theaetetus, that we have long been infected with logical impurity. Thousands of times have we repeated the words 'we know,' and 'do not know,' and 'we have or have not science or knowledge,' as if we could understand what we are saying to one another, so long as we remain ignorant about knowledge; and at this moment we are using the words 'we understand,' 'we are ignorant,' as though we could still employ them when deprived of knowledge or science. THEAETETUS: But if you avoid these expressions, Socrates, how will you ever argue at all?

SOCRATES: I could not, being the man I am. The case would be different if I were a true hero of dialectic: and O that such an one were present! for he would have told us to avoid the use of these terms; at the same time he would not have spared in you and me the faults which I have noted. But, seeing that we are no great wits, shall I venture to say what knowing is? for I think that the attempt may be worth making. THEAETETUS: Then by all means venture, and no one shall find fault with you for using the forbidden terms. SOCRATES: You have heard the common explanation of the verb 'to know'? THEAETETUS: I think so, but I do not remember it at the moment. SOCRATES: They explain the word 'to know' as meaning 'to have knowledge.' THEAETETUS: True. SOCRATES: I should like to make a slight change, and say 'to possess' knowledge. THEAETETUS: How do the two expressions differ? SOCRATES: Perhaps there may be no difference; but still I should like you to hear my view, that you may help me to test it. THEAETETUS: I will, if I can.

SOCRATES: I should distinguish 'having' from 'possessing': for example, a man may buy and keep under his control a garment which he does not wear; and then we should say, not that he has, but that he possesses the garment. THEAETETUS: It would be the correct expression. SOCRATES: Well, may not a man 'possess' and yet not 'have' knowledge in the sense of which I am speaking? As you may suppose a man to have caught wild birds - doves or any other birds - and to be keeping them in an aviary which he has constructed at home; we might say of him in one sense, that he always has them because he possesses them, might we not? THEAETETUS: Yes. SOCRATES: And yet, in another sense, he has none of them; but they are in his power, and he has got them under his hand in an enclosure of his own, and can take and have them whenever he likes; - he can catch any which he likes, and let the bird go again, and he may do so as often as he pleases. THEAETETUS: True.

SOCRATES: Once more, then, as in what preceded we made a sort of waxen figment in the mind, so let us now suppose that in the mind of each man there is an aviary of all sorts of birds - some flocking together apart from the rest, others in small groups, others solitary, flying anywhere and everywhere. THEAETETUS: Let us imagine such an aviary - and what is to follow? SOCRATES: We may suppose that the birds are kinds of knowledge, and that when we were children, this receptacle was empty; whenever a man has gotten and detained in the enclosure a kind of knowledge, he may be said to have learned or discovered the thing which is the subject of the knowledge: and this is to know. THEAETETUS: Granted. SOCRATES: And further, when any one wishes to catch any of these knowledges or sciences, and having taken, to hold it, and again to let them go, how will he express himself? - will he describe the 'catching' of them and the original 'possession' in the same words? I will make my meaning clearer by an example: - You admit that there is an art of arithmetic? THEAETETUS: To be sure. SOCRATES: Conceive this under the form of a hunt after the science of odd and even in general. THEAETETUS: I follow.

SOCRATES: Having the use of the art, the arithmetician, if I am not mistaken, has the conceptions of number under his hand, and can transmit them to another. THEAETETUS: Yes. SOCRATES: And when transmitting them he may be said to teach them, and when receiving to learn them, and when receiving to learn them, and when having them in possession in the aforesaid aviary he may be said to know them. THEAETETUS: Exactly. SOCRATES: Attend to what follows: must not the perfect arithmetician know all numbers, for he has the science of all numbers in his mind? THEAETETUS: True. SOCRATES: And he can reckon abstract numbers in his head, or things about him which are numerable? THEAETETUS: Of course he can. SOCRATES: And to reckon is simply to consider how much such and such a number amounts to? THEAETETUS: Very true. SOCRATES: And so he appears to be searching into something which he knows, as if he did not know it, for we have already admitted that he knows all numbers; - you have heard these perplexing questions raised? THEAETETUS: I have.

SOCRATES: May we not pursue the image of the doves, and say that the chase after knowledge is of two kinds? one kind is prior to possession and for the sake of possession, and the other for the sake of taking and holding in the hands that which is possessed already. And thus, when a man has learned and known something long ago, he may resume and get hold of the knowledge which he has long possessed, but has not at hand in his mind. THEAETETUS: True. SOCRATES: That was my reason for asking how we ought to speak when an arithmetician sets about numbering, or a grammarian about reading? Shall we say, that although he knows, he comes back to himself to learn what he already knows? THEAETETUS: It would be too absurd, Socrates. SOCRATES: Shall we say then that he is going to read or number what he does not know, although we have admitted that he knows all letters and all numbers? THEAETETUS: That, again, would be an absurdity.

SOCRATES: Then shall we say that about names we care nothing? - any one may twist and turn the words 'knowing' and 'learning' in any way which he likes, but since we have determined that the possession of knowledge is not the having or using it, we do assert that a man cannot not possess that which he possesses; and, therefore, in no case can a man not know that which he knows, but he may get a false opinion about it; for he may have the knowledge, not of this particular thing, but of some other; - when the various numbers and forms of knowledge are flying about in the aviary, and wishing to capture a certain sort of knowledge out of the general store, he takes the wrong one by mistake, that is to say, when he thought eleven to be twelve, he got hold of the ring-dove which he had in his mind, when he wanted the pigeon. THEAETETUS: A very rational explanation. SOCRATES: But when he catches the one which he wants, then he is not deceived, and has an opinion of what is, and thus false and true opinion may exist, and the difficulties which were previously raised disappear. I dare say that you agree with me, do you not? THEAETETUS: Yes.

SOCRATES: And so we are rid of the difficulty of a man's not knowing what he knows, for we are not driven to the inference that he does not possess what he possesses, whether he be or be not deceived. And yet I fear that a greater difficulty is looking in at the window. THEAETETUS: What is it? SOCRATES: How can the exchange of one knowledge for another ever become false opinion? THEAETETUS: What do you mean? SOCRATES: In the first place, how can a man who has the knowledge of anything be ignorant of that which he knows, not by reason of ignorance, but by reason of his own knowledge? And, again, is it not an extreme absurdity that he should suppose another thing to be this, and this to be another thing; - that, having knowledge present with him in his mind, he should still know nothing and be ignorant of all things? - you might as well argue that ignorance may make a man know, and blindness make him see, as that knowledge can make him ignorant.

THEAETETUS: Perhaps, Socrates, we may have been wrong in making only forms of knowledge our birds: whereas there ought to have been forms of ignorance as well, flying about together in the mind, and then he who sought to take one of them might sometimes catch a form of knowledge, and sometimes a form of ignorance; and thus he would have a false opinion from ignorance, but a true one from knowledge, about the same thing. SOCRATES: I cannot help praising you, Theaetetus, and yet I must beg you to reconsider your words. Let us grant what you say - then, according to you, he who takes ignorance will have a false opinion - am I right? THEAETETUS: Yes. SOCRATES: He will certainly not think that he has a false opinion? THEAETETUS: Of course not. SOCRATES: He will think that his opinion is true, and he will fancy that he knows the things about which he has been deceived? THEAETETUS: Certainly. SOCRATES: Then he will think that he has captured knowledge and not ignorance? THEAETETUS: Clearly.

SOCRATES: And thus, after going a long way round, we are once more face to face with our original difficulty. The hero of dialectic will retort upon us: - 'O my excellent friends, he will say, laughing, if a man knows the form of ignorance and the form of knowledge, can he think that one of them which he knows is the other which he knows? or, if he knows neither of them, can he think that the one which he knows not is another which he knows not? or, if he knows one and not the other, can he think the one which he knows to be the one which he does not know? or the one which he does not know to be the one which he knows? or will you tell me that there are other forms of knowledge which distinguish the right and wrong birds, and which the owner keeps in some other aviaries or graven on waxen blocks according to your foolish images, and which he may be said to know while he possesses them, even though he have them not at hand in his mind? And thus, in a perpetual circle, you will be compelled to go round and round, and you will make no progress.' What are we to say in reply, Theaetetus?

THEAETETUS: Indeed, Socrates, I do not know what we are to say. SOCRATES: Are not his reproaches just, and does not the argument truly show that we are wrong in seeking for false opinion until we know what knowledge is; that must be first ascertained; then, the nature of false opinion? THEAETETUS: I cannot but agree with you, Socrates, so far as we have yet gone. SOCRATES: Then, once more, what shall we say that knowledge is? - for we are not going to lose heart as yet. THEAETETUS: Certainly, I shall not lose heart, if you do not. SOCRATES: What definition will be most consistent with our former views? THEAETETUS: I cannot think of any but our old one, Socrates. SOCRATES: What was it? THEAETETUS: Knowledge was said by us to be true opinion; and true opinion is surely unerring, and the results which follow from it are all noble and good. SOCRATES: He who led the way into the river, Theaetetus, said 'The experiment will show;' and perhaps if we go forward in the search, we may stumble upon the thing which we are looking for; but if we stay where we are, nothing will come to light. THEAETETUS: Very true; let us go forward and try.

SOCRATES: The trail soon comes to an end, for a whole profession is against us. THEAETETUS: How is that, and what profession do you mean? SOCRATES: The profession of the great wise ones who are called orators and lawyers; for these persuade men by their art and make them think whatever they like, but they do not teach them. Do you imagine that there are any teachers in the world so clever as to be able to convince others of the truth about acts of robbery or violence, of which they were not eye-witnesses, while a little water is flowing in the clepsydra? THEAETETUS: Certainly not, they can only persuade them. SOCRATES: And would you not say that persuading them is making them have an opinion? THEAETETUS: To be sure. SOCRATES: When, therefore, judges are justly persuaded about matters which you can know only by seeing them, and not in any other way, and when thus judging of them from report they attain a true opinion about them, they judge without knowledge, and yet are rightly persuaded, if they have judged well. THEAETETUS: Certainly.

SOCRATES: And yet, O my friend, if true opinion in law courts and knowledge are the same, the perfect judge could not have judged rightly without knowledge; and therefore I must infer that they are not the same. THEAETETUS: That is a distinction, Socrates, which I have heard made by some one else, but I had forgotten it. He said that true opinion, combined with reason, was knowledge, but that the opinion which had no reason was out of the sphere of knowledge; and that things of which there is no rational account are not knowable - such was the singular expression which he used - and that things which have a reason or explanation are knowable. SOCRATES: Excellent; but then, how did he distinguish between things which are and are not 'knowable'? I wish that you would repeat to me what he said, and then I shall know whether you and I have heard the same tale. THEAETETUS: I do not know whether I can recall it; but if another person would tell me, I think that I could follow him.

SOCRATES: Let me give you, then, a dream in return for a dream: - Methought that I too had a dream, and I heard in my dream that the primeval letters or elements out of which you and I and all other things are compounded, have no reason or explanation; you can only name them, but no predicate can be either affirmed or denied of them, for in the one case existence, in the other non-existence is already implied, neither of which must be added, if you mean to speak of this or that thing by itself alone. It should not be called itself, or that, or each, or alone, or this, or the like; for these go about everywhere and are applied to all things, but are distinct from them; whereas, if the first elements could be described, and had a definition of their own, they would be spoken of apart from all else. But none of these primeval elements can be defined; they can only be named, for they have nothing but a name, and the things which are compounded of them, as they are complex, are expressed by a combination of names, for the combination of names is the essence of a definition. Thus, then, the elements or letters are only objects of perception, and cannot be defined or known; but the syllables or combinations of them are known and expressed, and are apprehended by true opinion. When, therefore, any one forms the true opinion of anything without rational explanation, you may say that his mind is truly exercised, but has no knowledge; for he who cannot give and receive a reason for a thing, has no knowledge of that thing; but when he adds rational explanation, then, he is perfected in knowledge and may be all that I have been denying of him. Was that the form in which the dream appeared to you?

THEAETETUS: Precisely. SOCRATES: And you allow and maintain that true opinion, combined with definition or rational explanation, is knowledge? THEAETETUS: Exactly. SOCRATES: Then may we assume, Theaetetus, that to-day, and in this casual manner, we have found a truth which in former times many wise men have grown old and have not found? THEAETETUS: At any rate, Socrates, I am satisfied with the present statement. SOCRATES: Which is probably correct - for how can there be knowledge apart from definition and true opinion? And yet there is one point in what has been said which does not quite satisfy me. THEAETETUS: What was it? SOCRATES: What might seem to be the most ingenious notion of all: - That the elements or letters are unknown, but the combination or syllables known. THEAETETUS: And was that wrong? SOCRATES: We shall soon know; for we have as hostages the instances which the author of the argument himself used. THEAETETUS: What hostages? SOCRATES: The letters, which are the clements; and the syllables, which are the combinations; - he reasoned, did he not, from the letters of the alphabet? THEAETETUS: Yes; he did.

SOCRATES: Let us take them and put them to the test, or rather, test ourselves: - What was the way in which we learned letters? and, first of all, are we right in saying that syllables have a definition, but that letters have no definition? THEAETETUS: I think so. SOCRATES: I think so too; for, suppose that some one asks you to spell the first syllable of my name: - Theaetetus, he says, what is SO? THEAETETUS: I should reply S and O. SOCRATES: That is the definition which you would give of the syllable? THEAETETUS: I should. SOCRATES: I wish that you would give me a similar definition of the S. THEAETETUS: But how can any one, Socrates, tell the elements of an element? I can only reply, that S is a consonant, a mere noise, as of the tongue hissing; B, and most other letters, again, are neither vowel-sounds nor noises. Thus letters may be most truly said to be undefined; for even the most distinct of them, which are the seven vowels, have a sound only, but no definition at all. SOCRATES: Then, I suppose, my friend, that we have been so far right in our idea about knowledge? THEAETETUS: Yes; I think that we have.

SOCRATES: Well, but have we been right in maintaining that the syllables can be known, but not the letters? THEAETETUS: I think so. SOCRATES: And do we mean by a syllable two letters, or if there are more, all of them, or a single idea which arises out of the combination of them? THEAETETUS: I should say that we mean all the letters. SOCRATES: Take the case of the two letters S and O, which form the first syllable of my own name; must not he who knows the syllable, know both of them? THEAETETUS: Certainly. SOCRATES: He knows, that is, the S and O? THEAETETUS: Yes. SOCRATES: But can he be ignorant of either singly and yet know both together? THEAETETUS: Such a supposition, Socrates, is monstrous and unmeaning. SOCRATES: But if he cannot know both without knowing each, then if he is ever to know the syllable, he must know the letters first; and thus the fine theory has again taken wings and departed. THEAETETUS: Yes, with wonderful celerity. SOCRATES: Yes, we did not keep watch properly. Perhaps we ought to have maintained that a syllable is not the letters, but rather one single idea framed out of them, having a separate form distinct from them. THEAETETUS: Very true; and a more likely notion than the other.

SOCRATES: Take care; let us not be cowards and betray a great and imposing theory. THEAETETUS: No, indeed. SOCRATES: Let us assume then, as we now say, that the syllable is a simple form arising out of the several combinations of harmonious elements - of letters or of any other elements. THEAETETUS: Very good. SOCRATES: And it must have no parts. THEAETETUS: Why? SOCRATES: Because that which has parts must be a whole of all the parts. Or would you say that a whole, although formed out of the parts, is a single notion different from all the parts? THEAETETUS: I should. SOCRATES: And would you say that all and the whole are the same, or different? THEAETETUS: I am not certain; but, as you like me to answer at once, I shall hazard the reply, that they are different. SOCRATES: I approve of your readiness, Theaetetus, but I must take time to think whether I equally approve of your answer. THEAETETUS: Yes; the answer is the point. SOCRATES: According to this new view, the whole is supposed to differ from all? THEAETETUS: Yes.

SOCRATES: Well, but is there any difference between all (in the plural) and the all (in the singular)? Take the case of number: - When we say one, two, three, four, five, six; or when we say twice three, or three times two, or four and two, or three and two and one, are we speaking of the same or of different numbers? THEAETETUS: Of the same. SOCRATES: That is of six? THEAETETUS: Yes. SOCRATES: And in each form of expression we spoke of all the six? THEAETETUS: True. SOCRATES: Again, in speaking of all (in the plural) is there not one thing which we express? THEAETETUS: Of course there is. SOCRATES: And that is six? THEAETETUS: Yes. SOCRATES: Then in predicating the word 'all' of things measured by number, we predicate at the same time a singular and a plural? THEAETETUS: Clearly we do. SOCRATES: Again, the number of the acre and the acre are the same; are they not? THEAETETUS: Yes. SOCRATES: And the number of the stadium in like manner is the stadium? THEAETETUS: Yes. SOCRATES: And the army is the number of the army; and in all similar cases, the entire number of anything is the entire thing? THEAETETUS: True. SOCRATES: And the number of each is the parts of each? THEAETETUS: Exactly.

SOCRATES: Then as many things as have parts are made up of parts? THEAETETUS: Clearly. SOCRATES: But all the parts are admitted to be the all, if the entire number is the all? THEAETETUS: True. SOCRATES: Then the whole is not made up of parts, for it would be the all, if consisting of all the parts? THEAETETUS: That is the inference. SOCRATES: But is a part a part of anything but the whole? THEAETETUS: Yes, of the all. SOCRATES: You make a valiant defence, Theaetetus. And yet is not the all that of which nothing is wanting? THEAETETUS: Certainly. SOCRATES: And is not a whole likewise that from which nothing is absent? but that from which anything is absent is neither a whole nor all; - if wanting in anything, both equally lose their entirety of nature. THEAETETUS: I now think that there is no difference between a whole and all. SOCRATES: But were we not saying that when a thing has parts, all the parts will be a whole and all? THEAETETUS: Certainly.

SOCRATES: Then, as I was saying before, must not the alternative be that either the syllable is not the letters, and then the letters are not parts of the syllable, or that the syllable will be the same with the letters, and will therefore be equally known with them? THEAETETUS: You are right. SOCRATES: And, in order to avoid this, we suppose it to be different from them? THEAETETUS: Yes. SOCRATES: But if letters are not parts of syllables, can you tell me of any other parts of syllables, which are not letters? THEAETETUS: No, indeed, Socrates; for if I admit the existence of parts in a syllable, it would be ridiculous in me to give up letters and seek for other parts. SOCRATES: Quite true, Theaetetus, and therefore, according to our present view, a syllable must surely be some indivisible form? THEAETETUS: True.

SOCRATES: But do you remember, my friend, that only a little while ago we admitted and approved the statement, that of the first elements out of which all other things are compounded there could be no definition, because each of them when taken by itself is uncompounded; nor can one rightly attribute to them the words 'being' or 'this,' because they are alien and inappropriate words, and for this reason the letters or elements were indefinable and unknown? THEAETETUS: I remember. SOCRATES: And is not this also the reason why they are simple and indivisible? I can see no other. THEAETETUS: No other reason can be given. SOCRATES: Then is not the syllable in the same case as the elements or letters, if it has no parts and is one form? THEAETETUS: To be sure. SOCRATES: If, then, a syllable is a whole, and has many parts or letters, the letters as well as the syllable must be intelligible and expressible, since all the parts are acknowledged to be the same as the whole? THEAETETUS: True. SOCRATES: But if it be one and indivisible, then the syllables and the letters are alike undefined and unknown, and for the same reason? THEAETETUS: I cannot deny that.

SOCRATES: We cannot, therefore, agree in the opinion of him who says that the syllable can be known and expressed, but not the letters. THEAETETUS: Certainly not; if we may trust the argument. SOCRATES: Well, but will you not be equally inclined to disagree with him, when you remember your own experience in learning to read? THEAETETUS: What experience? SOCRATES: Why, that in learning you were kept trying to distinguish the separate letters both by the eye and by the ear, in order that, when you heard them spoken or saw them written, you might not be confused by their position. THEAETETUS: Very true. SOCRATES: And is the education of the harp-player complete unless he can tell what string answers to a particular note; the notes, as every one would allow, are the elements or letters of music? THEAETETUS: Exactly. SOCRATES: Then, if we argue from the letters and syllables which we know to other simples and compounds, we shall say that the letters or simple elements as a class are much more certainly known than the syllables, and much more indispensable to a perfect knowledge of any subject; and if some one says that the syllable is known and the letter unknown, we shall consider that either intentionally or unintentionally he is talking nonsense? THEAETETUS: Exactly.

SOCRATES: And there might be given other proofs of this belief, if I am not mistaken. But do not let us in looking for them lose sight of the question before us, which is the meaning of the statement, that right opinion with rational definition or explanation is the most perfect form of knowledge. THEAETETUS: We must not. SOCRATES: Well, and what is the meaning of the term 'explanation'? I think that we have a choice of three meanings. THEAETETUS: What are they? SOCRATES: In the first place, the meaning may be, manifesting one's thought by the voice with verbs and nouns, imaging an opinion in the stream which flows from the lips, as in a mirror or water. Does not explanation appear to be of this nature? THEAETETUS: Certainly; he who so manifests his thought, is said to explain himself. SOCRATES: And every one who is not born deaf or dumb is able sooner or later to manifest what he thinks of anything; and if so, all those who have a right opinion about anything will also have right explanation; nor will right opinion be anywhere found to exist apart from knowledge. THEAETETUS: True.

SOCRATES: Let us not, therefore, hastily charge him who gave this account of knowledge with uttering an unmeaning word; for perhaps he only intended to say, that when a person was asked what was the nature of anything, he should be able to answer his questioner by giving the elements of the thing. THEAETETUS: As for example, Socrates...? SOCRATES: As, for example, when Hesiod says that a waggon is made up of a hundred planks. Now, neither you nor I could describe all of them individually; but if any one asked what is a waggon, we should be content to answer, that a waggon consists of wheels, axle, body, rims, yoke. THEAETETUS: Certainly. SOCRATES: And our opponent will probably laugh at us, just as he would if we professed to be grammarians and to give a grammatical account of the name of Theaetetus, and yet could only tell the syllables and not the letters of your name - that would be true opinion, and not knowledge; for knowledge, as has been already remarked, is not attained until, combined with true opinion, there is an enumeration of the elements out of which anything is composed. THEAETETUS: Yes.

SOCRATES: In the same general way, we might also have true opinion about a waggon; but he who can describe its essence by an enumeration of the hundred planks, adds rational explanation to true opinion, and instead of opinion has art and knowledge of the nature of a waggon, in that he attains to the whole through the elements. THEAETETUS: And do you not agree in that view, Socrates? SOCRATES: If you do, my friend; but I want to know first, whether you admit the resolution of all things into their elements to be a rational explanation of them, and the consideration of them in syllables or larger combinations of them to be irrational - is this your view? THEAETETUS: Precisely. SOCRATES: Well, and do you conceive that a man has knowledge of any element who at one time affirms and at another time denies that element of something, or thinks that the same thing is composed of different elements at different times? THEAETETUS: Assuredly not. SOCRATES: And do you not remember that in your case and in that of others this often occurred in the process of learning to read? THEAETETUS: You mean that I mistook the letters and misspelt the syllables? SOCRATES: Yes.

THEAETETUS: To be sure; I perfectly remember, and I am very far from supposing that they who are in this condition have knowledge. SOCRATES: When a person at the time of learning writes the name of Theaetetus, and thinks that he ought to write and does write Th and e; but, again, meaning to write the name of Theododorus, thinks that he ought to write and does write T and e - can we suppose that he knows the first syllables of your two names? THEAETETUS: We have already admitted that such a one has not yet attained knowledge. SOCRATES: And in like manner be may enumerate without knowing them the second and third and fourth syllables of your name? THEAETETUS: He may. SOCRATES: And in that case, when he knows the order of the letters and can write them out correctly, he has right opinion? THEAETETUS: Clearly. SOCRATES: But although we admit that he has right opinion, he will still be without knowledge? THEAETETUS: Yes. SOCRATES: And yet he will have explanation, as well as right opinion, for he knew the order of the letters when he wrote; and this we admit to be explanation. THEAETETUS: True.

SOCRATES: Then, my friend, there is such a thing as right opinion united with definition or explanation, which does not as yet attain to the exactness of knowledge. THEAETETUS: It would seem so. SOCRATES: And what we fancied to be a perfect definition of knowledge is a dream only. But perhaps we had better not say so as yet, for were there not three explanations of knowledge, one of which must, as we said, be adopted by him who maintains knowledge to be true opinion combined with rational explanation? And very likely there may be found some one who will not prefer this but the third. THEAETETUS: You are quite right; there is still one remaining. The first was the image or expression of the mind in speech; the second, which has just been mentioned, is a way of reaching the whole by an enumeration of the elements. But what is the third definition? SOCRATES: There is, further, the popular notion of telling the mark or sign of difference which distinguishes the thing in question from all others. THEAETETUS: Can you give me any example of such a definition?

SOCRATES: As, for example, in the case of the sun, I think that you would be contented with the statement that the sun is the brightest of the heavenly bodies which revolve about the earth. THEAETETUS: Certainly. SOCRATES: Understand why: - the reason is, as I was just now saying, that if you get at the difference and distinguishing characteristic of each thing, then, as many persons affirm, you will get at the definition or explanation of it; but while you lay hold only of the common and not of the characteristic notion, you will only have the definition of those things to which this common quality belongs. THEAETETUS: I understand you, and your account of definition is in my judgment correct. SOCRATES: But he, who having right opinion about anything, can find out the difference which distinguishes it from other things will know that of which before he had only an opinion. THEAETETUS: Yes; that is what we are maintaining. SOCRATES: Nevertheless, Theaetetus, on a nearer view, I find myself quite disappointed; the picture, which at a distance was not so bad, has now become altogether unintelligible. THEAETETUS: What do you mean?

SOCRATES: I will endeavour to explain: I will suppose myself to have true opinion of you, and if to this I add your definition, then I have knowledge, but if not, opinion only. THEAETETUS: Yes. SOCRATES: The definition was assumed to be the interpretation of your difference. THEAETETUS: True. SOCRATES: But when I had only opinion, I had no conception of your distinguishing characteristics. THEAETETUS: I suppose not. SOCRATES: Then I must have conceived of some general or common nature which no more belonged to you than to another. THEAETETUS: True. SOCRATES: Tell me, now - How in that case could I have formed a judgment of you any more than of any one else? Suppose that I imagine Theaetetus to be a man who has nose, eyes, and mouth, and every other member complete; how would that enable me to distinguish Theaetetus from Theodorus, or from some outer barbarian? THEAETETUS: How could it? SOCRATES: Or if I had further conceived of you, not only as having nose and eyes, but as having a snub nose and prominent eyes, should I have any more notion of you than of myself and others who resemble me? THEAETETUS: Certainly not.