Theaetetus

PERSONS OF THE DIALOGUE: Socrates, Theodorus, Theaetetus. Euclid and Terpsion meet in front of Euclid's house in Megara; they enter the house, and the dialogue is read to them by a servant. EUCLID: Have you only just arrived from the country, Terpsion? TERPSION: No, I came some time ago: and I have been in the Agora looking for you, and wondering that I could not find you. EUCLID: But I was not in the city. TERPSION: Where then? EUCLID: As I was going down to the harbour, I met Theaetetus - he was being carried up to Athens from the army at Corinth. TERPSION: Was he alive or dead? EUCLID: He was scarcely alive, for he has been badly wounded; but he was suffering even more from the sickness which has broken out in the army. TERPSION: The dysentery, you mean? EUCLID: Yes. TERPSION: Alas! what a loss he will be! EUCLID: Yes, Terpsion, he is a noble fellow; only to-day I heard some people highly praising his behaviour in this very battle. TERPSION: No wonder; I should rather be surprised at hearing anything else of him. But why did he go on, instead of stopping at Megara?

EUCLID: He wanted to get home: although I entreated and advised him to remain, he would not listen to me; so I set him on his way, and turned back, and then I remembered what Socrates had said of him, and thought how remarkably this, like all his predictions, had been fulfilled. I believe that he had seen him a little before his own death, when Theaetetus was a youth, and he had a memorable conversation with him, which he repeated to me when I came to Athens; he was full of admiration of his genius, and said that he would most certainly be a great man, if he lived. TERPSION: The prophecy has certainly been fulfilled; but what was the conversation? can you tell me? EUCLID: No, indeed, not offhand; but I took notes of it as soon as I got home; these I filled up from memory, writing them out at leisure; and whenever I went to Athens, I asked Socrates about any point which I had forgotten, and on my return I made corrections; thus I have nearly the whole conversation written down.

TERPSION: I remember - you told me; and I have always been intending to ask you to show me the writing, but have put off doing so; and now, why should we not read it through? - having just come from the country, I should greatly like to rest. EUCLID: I too shall be very glad of a rest, for I went with Theaetetus as far as Erineum. Let us go in, then, and, while we are reposing, the servant shall read to us. TERPSION: Very good. EUCLID: Here is the roll, Terpsion; I may observe that I have introduced Socrates, not as narrating to me, but as actually conversing with the persons whom he mentioned - these were, Theodorus the geometrician (of Cyrene), and Theaetetus. I have omitted, for the sake of convenience, the interlocutory words 'I said,' 'I remarked,' which he used when he spoke of himself, and again, 'he agreed,' or 'disagreed,' in the answer, lest the repetition of them should be troublesome. TERPSION: Quite right, Euclid. EUCLID: And now, boy, you may take the roll and read. EUCLID'S SERVANT READS.

SOCRATES: If I cared enough about the Cyrenians, Theodorus, I would ask you whether there are any rising geometricians or philosophers in that part of the world. But I am more interested in our own Athenian youth, and I would rather know who among them are likely to do well. I observe them as far as I can myself, and I enquire of any one whom they follow, and I see that a great many of them follow you, in which they are quite right, considering your eminence in geometry and in other ways. Tell me then, if you have met with any one who is good for anything.

THEODORUS: Yes, Socrates, I have become acquainted with one very remarkable Athenian youth, whom I commend to you as well worthy of your attention. If he had been a beauty I should have been afraid to praise him, lest you should suppose that I was in love with him; but he is no beauty, and you must not be offended if I say that he is very like you; for he has a snub nose and projecting eyes, although these features are less marked in him than in you. Seeing, then, that he has no personal attractions, I may freely say, that in all my acquaintance, which is very large, I never knew any one who was his equal in natural gifts: for he has a quickness of apprehension which is almost unrivalled, and he is exceedingly gentle, and also the most courageous of men; there is a union of qualities in him such as I have never seen in any other, and should scarcely have thought possible; for those who, like him, have quick and ready and retentive wits, have generally also quick tempers; they are ships without ballast, and go darting about, and are mad rather than courageous; and the steadier sort, when they have to face study, prove stupid and cannot remember. Whereas he moves surely and smoothly and successfully in the path of knowledge and enquiry; and he is full of gentleness, flowing on silently like a river of oil; at his age, it is wonderful.

SOCRATES: That is good news; whose son is he? THEODORUS: The name of his father I have forgotten, but the youth himself is the middle one of those who are approaching us; he and his companions have been anointing themselves in the outer court, and now they seem to have finished, and are coming towards us. Look and see whether you know him. SOCRATES: I know the youth, but I do not know his name; he is the son of Euphronius the Sunian, who was himself an eminent man, and such another as his son is, according to your account of him; I believe that he left a considerable fortune. THEODORUS: Theaetetus, Socrates, is his name; but I rather think that the property disappeared in the hands of trustees; notwithstanding which he is wonderfully liberal. SOCRATES: He must be a fine fellow; tell him to come and sit by me. THEODORUS: I will. Come hither, Theaetetus, and sit by Socrates.

SOCRATES: By all means, Theaetetus, in order that I may see the reflection of myself in your face, for Theodorus says that we are alike; and yet if each of us held in his hands a lyre, and he said that they were tuned alike, should we at once take his word, or should we ask whether he who said so was or was not a musician? THEAETETUS: We should ask. SOCRATES: And if we found that he was, we should take his word; and if not, not? THEAETETUS: True. SOCRATES: And if this supposed likeness of our faces is a matter of any interest to us, we should enquire whether he who says that we are alike is a painter or not? THEAETETUS: Certainly we should. SOCRATES: And is Theodorus a painter? THEAETETUS: I never heard that he was. SOCRATES: Is he a geometrician? THEAETETUS: Of course he is, Socrates. SOCRATES: And is he an astronomer and calculator and musician, and in general an educated man? THEAETETUS: I think so. SOCRATES: If, then, he remarks on a similarity in our persons, either by way of praise or blame, there is no particular reason why we should attend to him. THEAETETUS: I should say not.

SOCRATES: But if he praises the virtue or wisdom which are the mental endowments of either of us, then he who hears the praises will naturally desire to examine him who is praised: and he again should be willing to exhibit himself. THEAETETUS: Very true, Socrates. SOCRATES: Then now is the time, my dear Theaetetus, for me to examine, and for you to exhibit; since although Theodorus has praised many a citizen and stranger in my hearing, never did I hear him praise any one as he has been praising you. THEAETETUS: I am glad to hear it, Socrates; but what if he was only in jest? SOCRATES: Nay, Theodorus is not given to jesting; and I cannot allow you to retract your consent on any such pretence as that. If you do, he will have to swear to his words; and we are perfectly sure that no one will be found to impugn him. Do not be shy then, but stand to your word. THEAETETUS: I suppose I must, if you wish it. SOCRATES: In the first place, I should like to ask what you learn of Theodorus: something of geometry, perhaps? THEAETETUS: Yes. SOCRATES: And astronomy and harmony and calculation? THEAETETUS: I do my best.

SOCRATES: Yes, my boy, and so do I; and my desire is to learn of him, or of anybody who seems to understand these things. And I get on pretty well in general; but there is a little difficulty which I want you and the company to aid me in investigating. Will you answer me a question: 'Is not learning growing wiser about that which you learn?' THEAETETUS: Of course. SOCRATES: And by wisdom the wise are wise? THEAETETUS: Yes. SOCRATES: And is that different in any way from knowledge? THEAETETUS: What? SOCRATES: Wisdom; are not men wise in that which they know? THEAETETUS: Certainly they are. SOCRATES: Then wisdom and knowledge are the same? THEAETETUS: Yes.

SOCRATES: Herein lies the difficulty which I can never solve to my satisfaction - What is knowledge? Can we answer that question? What say you? which of us will speak first? whoever misses shall sit down, as at a game of ball, and shall be donkey, as the boys say; he who lasts out his competitors in the game without missing, shall be our king, and shall have the right of putting to us any questions which he pleases...Why is there no reply? I hope, Theodorus, that I am not betrayed into rudeness by my love of conversation? I only want to make us talk and be friendly and sociable. THEODORUS: The reverse of rudeness, Socrates: but I would rather that you would ask one of the young fellows; for the truth is, that I am unused to your game of question and answer, and I am too old to learn; the young will be more suitable, and they will improve more than I shall, for youth is always able to improve. And so having made a beginning with Theaetetus, I would advise you to go on with him and not let him off.

SOCRATES: Do you hear, Theaetetus, what Theodorus says? The philosopher, whom you would not like to disobey, and whose word ought to be a command to a young man, bids me interrogate you. Take courage, then, and nobly say what you think that knowledge is. THEAETETUS: Well, Socrates, I will answer as you and he bid me; and if I make a mistake, you will doubtless correct me. SOCRATES: We will, if we can. THEAETETUS: Then, I think that the sciences which I learn from Theodorus - geometry, and those which you just now mentioned - are knowledge; and I would include the art of the cobbler and other craftsmen; these, each and all of, them, are knowledge. SOCRATES: Too much, Theaetetus, too much; the nobility and liberality of your nature make you give many and diverse things, when I am asking for one simple thing. THEAETETUS: What do you mean, Socrates? SOCRATES: Perhaps nothing. I will endeavour, however, to explain what I believe to be my meaning: When you speak of cobbling, you mean the art or science of making shoes? THEAETETUS: Just so. SOCRATES: And when you speak of carpentering, you mean the art of making wooden implements? THEAETETUS: I do. SOCRATES: In both cases you define the subject matter of each of the two arts? THEAETETUS: True.

SOCRATES: And when a man is asked what science or knowledge is, to give in answer the name of some art or science is ridiculous; for the question is, 'What is knowledge?' and he replies, 'A knowledge of this or that.' THEAETETUS: True. SOCRATES: Moreover, he might answer shortly and simply, but he makes an enormous circuit. For example, when asked about the clay, he might have said simply, that clay is moistened earth - what sort of clay is not to the point. THEAETETUS: Yes, Socrates, there is no difficulty as you put the question. You mean, if I am not mistaken, something like what occurred to me and to my friend here, your namesake Socrates, in a recent discussion. SOCRATES: What was that, Theaetetus? THEAETETUS: Theodorus was writing out for us something about roots, such as the roots of three or five, showing that they are incommensurable by the unit: he selected other examples up to seventeen - there he stopped. Now as there are innumerable roots, the notion occurred to us of attempting to include them all under one name or class. SOCRATES: And did you find such a class? THEAETETUS: I think that we did; but I should like to have your opinion. SOCRATES: Let me hear.

THEAETETUS: We divided all numbers into two classes: those which are made up of equal factors multiplying into one another, which we compared to square figures and called square or equilateral numbers; - that was one class. SOCRATES: Very good. THEAETETUS: The intermediate numbers, such as three and five, and every other number which is made up of unequal factors, either of a greater multiplied by a less, or of a less multiplied by a greater, and when regarded as a figure, is contained in unequal sides; - all these we compared to oblong figures, and called them oblong numbers. SOCRATES: Capital; and what followed? THEAETETUS: The lines, or sides, which have for their squares the equilateral plane numbers, were called by us lengths or magnitudes; and the lines which are the roots of (or whose squares are equal to) the oblong numbers, were called powers or roots; the reason of this latter name being, that they are commensurable with the former [i.e., with the so-called lengths or magnitudes] not in linear measurement, but in the value of the superficial content of their squares; and the same about solids. SOCRATES: Excellent, my boys; I think that you fully justify the praises of Theodorus, and that he will not be found guilty of false witness.

THEAETETUS: But I am unable, Socrates, to give you a similar answer about knowledge, which is what you appear to want; and therefore Theodorus is a deceiver after all. SOCRATES: Well, but if some one were to praise you for running, and to say that he never met your equal among boys, and afterwards you were beaten in a race by a grown-up man, who was a great runner - would the praise be any the less true? THEAETETUS: Certainly not. SOCRATES: And is the discovery of the nature of knowledge so small a matter, as just now said? Is it not one which would task the powers of men perfect in every way? THEAETETUS: By heaven, they should be the top of all perfection! SOCRATES: Well, then, be of good cheer; do not say that Theodorus was mistaken about you, but do your best to ascertain the true nature of knowledge, as well as of other things. THEAETETUS: I am eager enough, Socrates, if that would bring to light the truth. SOCRATES: Come, you made a good beginning just now; let your own answer about roots be your model, and as you comprehended them all in one class, try and bring the many sorts of knowledge under one definition.

THEAETETUS: I can assure you, Socrates, that I have tried very often, when the report of questions asked by you was brought to me; but I can neither persuade myself that I have a satisfactory answer to give, nor hear of any one who answers as you would have him; and I cannot shake off a feeling of anxiety. SOCRATES: These are the pangs of labour, my dear Theaetetus; you have something within you which you are bringing to the birth. THEAETETUS: I do not know, Socrates; I only say what I feel. SOCRATES: And have you never heard, simpleton, that I am the son of a midwife, brave and burly, whose name was Phaenarete? THEAETETUS: Yes, I have. SOCRATES: And that I myself practise midwifery? THEAETETUS: No, never. SOCRATES: Let me tell you that I do though, my friend: but you must not reveal the secret, as the world in general have not found me out; and therefore they only say of me, that I am the strangest of mortals and drive men to their wits' end. Did you ever hear that too? THEAETETUS: Yes. SOCRATES: Shall I tell you the reason? THEAETETUS: By all means.

SOCRATES: Bear in mind the whole business of the midwives, and then you will see my meaning better: - No woman, as you are probably aware, who is still able to conceive and bear, attends other women, but only those who are past bearing. THEAETETUS: Yes, I know. SOCRATES: The reason of this is said to be that Artemis - the goddess of childbirth - is not a mother, and she honours those who are like herself; but she could not allow the barren to be midwives, because human nature cannot know the mystery of an art without experience; and therefore she assigned this office to those who are too old to bear. THEAETETUS: I dare say. SOCRATES: And I dare say too, or rather I am absolutely certain, that the midwives know better than others who is pregnant and who is not? THEAETETUS: Very true. SOCRATES: And by the use of potions and incantations they are able to arouse the pangs and to soothe them at will; they can make those bear who have a difficulty in bearing, and if they think fit they can smother the embryo in the womb. THEAETETUS: They can. SOCRATES: Did you ever remark that they are also most cunning matchmakers, and have a thorough knowledge of what unions are likely to produce a brave brood? THEAETETUS: No, never.

SOCRATES: Then let me tell you that this is their greatest pride, more than cutting the umbilical cord. And if you reflect, you will see that the same art which cultivates and gathers in the fruits of the earth, will be most likely to know in what soils the several plants or seeds should be deposited. THEAETETUS: Yes, the same art. SOCRATES: And do you suppose that with women the case is otherwise? THEAETETUS: I should think not. SOCRATES: Certainly not; but midwives are respectable women who have a character to lose, and they avoid this department of their profession, because they are afraid of being called procuresses, which is a name given to those who join together man and woman in an unlawful and unscientific way; and yet the true midwife is also the true and only matchmaker. THEAETETUS: Clearly. SOCRATES: Such are the midwives, whose task is a very important one, but not so important as mine; for women do not bring into the world at one time real children, and at another time counterfeits which are with difficulty distinguished from them; if they did, then the discernment of the true and false birth would be the crowning achievement of the art of midwifery - you would think so? THEAETETUS: Indeed I should.

SOCRATES: Well, my art of midwifery is in most respects like theirs; but differs, in that I attend men and not women; and look after their souls when they are in labour, and not after their bodies: and the triumph of my art is in thoroughly examining whether the thought which the mind of the young man brings forth is a false idol or a noble and true birth. And like the midwives, I am barren, and the reproach which is often made against me, that I ask questions of others and have not the wit to answer them myself, is very just - the reason is, that the god compels me to be a midwife, but does not allow me to bring forth. And therefore I am not myself at all wise, nor have I anything to show which is the invention or birth of my own soul, but those who converse with me profit. Some of them appear dull enough at first, but afterwards, as our acquaintance ripens, if the god is gracious to them, they all make astonishing progress; and this in the opinion of others as well as in their own. It is quite clear that they never learned anything from me; the many fine discoveries to which they cling are of their own making. But to me

and the god they owe their delivery. And the proof of my words is, that many of them in their ignorance, either in their self-conceit despising me, or falling under the influence of others, have gone away too soon; and have not only lost the children of whom I had previously delivered them by an ill bringing up, but have stifled whatever else they had in them by evil communications, being fonder of lies and shams than of the truth; and they have at last ended by seeing themselves, as others see them, to be great fools. Aristeides, the son of Lysimachus, is one of them, and there are many others. The truants often return to me, and beg that I would consort with them again - they are ready to go to me on their knees - and then, if my familiar allows, which is not always the case, I receive them, and they begin to grow again. Dire are the pangs which my art is able to arouse and to allay in those who consort with me, just like the pangs of women in childbirth; night and day they are full of perplexity and travail which is even worse than that of the women. So much for them. And there are others, Theaetetus, who come to me apparently having nothing in them;

and as I know that they have no need of my art, I coax them into marrying some one, and by the grace of God I can generally tell who is likely to do them good. Many of them I have given away to Prodicus, and many to other inspired sages. I tell you this long story, friend Theaetetus, because I suspect, as indeed you seem to think yourself, that you are in labour - great with some conception. Come then to me, who am a midwife's son and myself a midwife, and do your best to answer the questions which I will ask you. And if I abstract and expose your first-born, because I discover upon inspection that the conception which you have formed is a vain shadow, do not quarrel with me on that account, as the manner of women is when their first children are taken from them. For I have actually known some who were ready to bite me when I deprived them of a darling folly; they did not perceive that I acted from goodwill, not knowing that no god is the enemy of man - that was not within the range of their ideas; neither am I their enemy in all this, but it would be wrong for me to admit falsehood, or to stifle the truth. Once

more, then, Theaetetus, I repeat my old question, 'What is knowledge?' - and do not say that you cannot tell; but quit yourself like a man, and by the help of God you will be able to tell.

THEAETETUS: At any rate, Socrates, after such an exhortation I should be ashamed of not trying to do my best. Now he who knows perceives what he knows, and, as far as I can see at present, knowledge is perception. SOCRATES: Bravely said, boy; that is the way in which you should express your opinion. And now, let us examine together this conception of yours, and see whether it is a true birth or a mere wind-egg: - You say that knowledge is perception? THEAETETUS: Yes. SOCRATES: Well, you have delivered yourself of a very important doctrine about knowledge; it is indeed the opinion of Protagoras, who has another way of expressing it. Man, he says, is the measure of all things, of the existence of things that are, and of the non-existence of things that are not: - You have read him? THEAETETUS: O yes, again and again. SOCRATES: Does he not say that things are to you such as they appear to you, and to me such as they appear to me, and that you and I are men? THEAETETUS: Yes, he says so.

SOCRATES: A wise man is not likely to talk nonsense. Let us try to understand him: the same wind is blowing, and yet one of us may be cold and the other not, or one may be slightly and the other very cold? THEAETETUS: Quite true. SOCRATES: Now is the wind, regarded not in relation to us but absolutely, cold or not; or are we to say, with Protagoras, that the wind is cold to him who is cold, and not to him who is not? THEAETETUS: I suppose the last. SOCRATES: Then it must appear so to each of them? THEAETETUS: Yes. SOCRATES: And 'appears to him' means the same as 'he perceives.' THEAETETUS: True. SOCRATES: Then appearing and perceiving coincide in the case of hot and cold, and in similar instances; for things appear, or may be supposed to be, to each one such as he perceives them? THEAETETUS: Yes. SOCRATES: Then perception is always of existence, and being the same as knowledge is unerring? THEAETETUS: Clearly.

SOCRATES: In the name of the Graces, what an almighty wise man Protagoras must have been! He spoke these things in a parable to the common herd, like you and me, but told the truth, 'his Truth,' (In allusion to a book of Protagoras' which bore this title.) in secret to his own disciples. THEAETETUS: What do you mean, Socrates? SOCRATES: I am about to speak of a high argument, in which all things are said to be relative; you cannot rightly call anything by any name, such as great or small, heavy or light, for the great will be small and the heavy light - there is no single thing or quality, but out of motion and change and admixture all things are becoming relatively to one another, which 'becoming' is by us incorrectly called being, but is really becoming, for nothing ever is, but all things are becoming. Summon all philosophers - Protagoras, Heracleitus, Empedocles, and the rest of them, one after another, and with the exception of Parmenides they will agree with you in this. Summon the great masters of either kind of poetry - Epicharmus, the prince of Comedy, and Homer of Tragedy; when the latter sings of 'Ocean whence sprang the gods, and mother Tethys,' does he not mean that all things are the offspring, of flux and motion?

THEAETETUS: I think so. SOCRATES: And who could take up arms against such a great army having Homer for its general, and not appear ridiculous? (Compare Cratylus.) THEAETETUS: Who indeed, Socrates? SOCRATES: Yes, Theaetetus; and there are plenty of other proofs which will show that motion is the source of what is called being and becoming, and inactivity of not-being and destruction; for fire and warmth, which are supposed to be the parent and guardian of all other things, are born of movement and of friction, which is a kind of motion; - is not this the origin of fire? THEAETETUS: It is. SOCRATES: And the race of animals is generated in the same way? THEAETETUS: Certainly. SOCRATES: And is not the bodily habit spoiled by rest and idleness, but preserved for a long time by motion and exercise? THEAETETUS: True. SOCRATES: And what of the mental habit? Is not the soul informed, and improved, and preserved by study and attention, which are motions; but when at rest, which in the soul only means want of attention and study, is uninformed, and speedily forgets whatever she has learned? THEAETETUS: True. SOCRATES: Then motion is a good, and rest an evil, to the soul as well as to the body? THEAETETUS: Clearly.

SOCRATES: I may add, that breathless calm, stillness and the like waste and impair, while wind and storm preserve; and the palmary argument of all, which I strongly urge, is the golden chain in Homer, by which he means the sun, thereby indicating that so long as the sun and the heavens go round in their orbits, all things human and divine are and are preserved, but if they were chained up and their motions ceased, then all things would be destroyed, and, as the saying is, turned upside down. THEAETETUS: I believe, Socrates, that you have truly explained his meaning. SOCRATES: Then now apply his doctrine to perception, my good friend, and first of all to vision; that which you call white colour is not in your eyes, and is not a distinct thing which exists out of them. And you must not assign any place to it: for if it had position it would be, and be at rest, and there would be no process of becoming. THEAETETUS: Then what is colour?

SOCRATES: Let us carry the principle which has just been affirmed, that nothing is self-existent, and then we shall see that white, black, and every other colour, arises out of the eye meeting the appropriate motion, and that what we call a colour is in each case neither the active nor the passive element, but something which passes between them, and is peculiar to each percipient; are you quite certain that the several colours appear to a dog or to any animal whatever as they appear to you? THEAETETUS: Far from it. SOCRATES: Or that anything appears the same to you as to another man? Are you so profoundly convinced of this? Rather would it not be true that it never appears exactly the same to you, because you are never exactly the same? THEAETETUS: The latter.

SOCRATES: And if that with which I compare myself in size, or which I apprehend by touch, were great or white or hot, it could not become different by mere contact with another unless it actually changed; nor again, if the comparing or apprehending subject were great or white or hot, could this, when unchanged from within, become changed by any approximation or affection of any other thing. The fact is that in our ordinary way of speaking we allow ourselves to be driven into most ridiculous and wonderful contradictions, as Protagoras and all who take his line of argument would remark. THEAETETUS: How? and of what sort do you mean? SOCRATES: A little instance will sufficiently explain my meaning: Here are six dice, which are more by a half when compared with four, and fewer by a half than twelve - they are more and also fewer. How can you or any one maintain the contrary? THEAETETUS: Very true. SOCRATES: Well, then, suppose that Protagoras or some one asks whether anything can become greater or more if not by increasing, how would you answer him, Theaetetus? THEAETETUS: I should say 'No,' Socrates, if I were to speak my mind in reference to this last question, and if I were not afraid of contradicting my former answer.

SOCRATES: Capital! excellent! spoken like an oracle, my boy! And if you reply 'Yes,' there will be a case for Euripides; for our tongue will be unconvinced, but not our mind. (In allusion to the well-known line of Euripides, Hippol.: e gloss omomoch e de thren anomotos.) THEAETETUS: Very true. SOCRATES: The thoroughbred Sophists, who know all that can be known about the mind, and argue only out of the superfluity of their wits, would have had a regular sparring-match over this, and would have knocked their arguments together finely. But you and I, who have no professional aims, only desire to see what is the mutual relation of these principles, - whether they are consistent with each or not. THEAETETUS: Yes, that would be my desire. SOCRATES: And mine too. But since this is our feeling, and there is plenty of time, why should we not calmly and patiently review our own thoughts, and thoroughly examine and see what these appearances in us really are? If I am not mistaken, they will be described by us as follows: - first, that nothing can become greater or less, either in number or magnitude, while remaining equal to itself - you would agree? THEAETETUS: Yes. SOCRATES: Secondly, that without addition or subtraction there is no increase or diminution of anything, but only equality. THEAETETUS: Quite true.

SOCRATES: Thirdly, that what was not before cannot be afterwards, without becoming and having become. THEAETETUS: Yes, truly. SOCRATES: These three axioms, if I am not mistaken, are fighting with one another in our minds in the case of the dice, or, again, in such a case as this - if I were to say that I, who am of a certain height and taller than you, may within a year, without gaining or losing in height, be not so tall - not that I should have lost, but that you would have increased. In such a case, I am afterwards what I once was not, and yet I have not become; for I could not have become without becoming, neither could I have become less without losing somewhat of my height; and I could give you ten thousand examples of similar contradictions, if we admit them at all. I believe that you follow me, Theaetetus; for I suspect that you have thought of these questions before now. THEAETETUS: Yes, Socrates, and I am amazed when I think of them; by the Gods I am! and I want to know what on earth they mean; and there are times when my head quite swims with the contemplation of them.

SOCRATES: I see, my dear Theaetetus, that Theodorus had a true insight into your nature when he said that you were a philosopher, for wonder is the feeling of a philosopher, and philosophy begins in wonder. He was not a bad genealogist who said that Iris (the messenger of heaven) is the child of Thaumas (wonder). But do you begin to see what is the explanation of this perplexity on the hypothesis which we attribute to Protagoras? THEAETETUS: Not as yet. SOCRATES: Then you will be obliged to me if I help you to unearth the hidden 'truth' of a famous man or school. THEAETETUS: To be sure, I shall be very much obliged. SOCRATES: Take a look round, then, and see that none of the uninitiated are listening. Now by the uninitiated I mean the people who believe in nothing but what they can grasp in their hands, and who will not allow that action or generation or anything invisible can have real existence. THEAETETUS: Yes, indeed, Socrates, they are very hard and impenetrable mortals.

SOCRATES: Yes, my boy, outer barbarians. Far more ingenious are the brethren whose mysteries I am about to reveal to you. Their first principle is, that all is motion, and upon this all the affections of which we were just now speaking are supposed to depend: there is nothing but motion, which has two forms, one active and the other passive, both in endless number; and out of the union and friction of them there is generated a progeny endless in number, having two forms, sense and the object of sense, which are ever breaking forth and coming to the birth at the same moment. The senses are variously named hearing, seeing, smelling; there is the sense of heat, cold, pleasure, pain, desire, fear, and many more which have names, as well as innumerable others which are without them; each has its kindred object, - each variety of colour has a corresponding variety of sight, and so with sound and hearing, and with the rest of the senses and the objects akin to them. Do you see, Theaetetus, the bearings of this tale on the preceding argument? THEAETETUS: Indeed I do not.

SOCRATES: Then attend, and I will try to finish the story. The purport is that all these things are in motion, as I was saying, and that this motion is of two kinds, a slower and a quicker; and the slower elements have their motions in the same place and with reference to things near them, and so they beget; but what is begotten is swifter, for it is carried to fro, and moves from place to place. Apply this to sense: - When the eye and the appropriate object meet together and give birth to whiteness and the sensation connatural with it, which could not have been given by either of them going elsewhere, then, while the sight is flowing from the eye, whiteness proceeds from the object which combines in producing the colour; and so the eye is fulfilled with sight, and really sees, and becomes, not sight, but a seeing eye; and the object which combined to form the colour is fulfilled with whiteness, and becomes not whiteness but a white thing, whether wood or stone or whatever the object may be which happens to be coloured white. And this is true of all sensible objects, hard, warm, and the like, which are similarly to be regarded, as I was saying before, not as having any absolute existence, but

as being all of them of whatever kind generated by motion in their intercourse with one another; for of the agent and patient, as existing in separation, no trustworthy conception, as they say, can be formed, for the agent has no existence until united with the patient, and the patient has no existence until united with the agent; and that which by uniting with something becomes an agent, by meeting with some other thing is converted into a patient. And from all these considerations, as I said at first, there arises a general reflection, that there is no one self-existent thing, but everything is becoming and in relation; and being must be altogether abolished, although from habit and ignorance we are compelled even in this discussion to retain the use of the term. But great philosophers tell us that we are not to allow either the word 'something,' or 'belonging to something,' or 'to me,' or 'this,' or 'that,' or any other detaining name to be used, in the language of nature all things are being created and destroyed, coming into being and passing into new forms; nor can any name fix or detain them; he who attempts to fix them is easily refuted. And this should be the way of speaking, not only of particulars but of aggregates; such

THEAETETUS: I do not know what to say, Socrates; for, indeed, I cannot make out whether you are giving your own opinion or only wanting to draw me out. SOCRATES: You forget, my friend, that I neither know, nor profess to know, anything of these matters; you are the person who is in labour, I am the barren midwife; and this is why I soothe you, and offer you one good thing after another, that you may taste them. And I hope that I may at last help to bring your own opinion into the light of day: when this has been accomplished, then we will determine whether what you have brought forth is only a wind-egg or a real and genuine birth. Therefore, keep up your spirits, and answer like a man what you think. THEAETETUS: Ask me. SOCRATES: Then once more: Is it your opinion that nothing is but what becomes? - the good and the noble, as well as all the other things which we were just now mentioning? THEAETETUS: When I hear you discoursing in this style, I think that there is a great deal in what you say, and I am very ready to assent.

SOCRATES: Let us not leave the argument unfinished, then; for there still remains to be considered an objection which may be raised about dreams and diseases, in particular about madness, and the various illusions of hearing and sight, or of other senses. For you know that in all these cases the esse-percipi theory appears to be unmistakably refuted, since in dreams and illusions we certainly have false perceptions; and far from saying that everything is which appears, we should rather say that nothing is which appears. THEAETETUS: Very true, Socrates. SOCRATES: But then, my boy, how can any one contend that knowledge is perception, or that to every man what appears is? THEAETETUS: I am afraid to say, Socrates, that I have nothing to answer, because you rebuked me just now for making this excuse; but I certainly cannot undertake to argue that madmen or dreamers think truly, when they imagine, some of them that they are gods, and others that they can fly, and are flying in their sleep. SOCRATES: Do you see another question which can be raised about these phenomena, notably about dreaming and waking? THEAETETUS: What question?

SOCRATES: A question which I think that you must often have heard persons ask: - How can you determine whether at this moment we are sleeping, and all our thoughts are a dream; or whether we are awake, and talking to one another in the waking state? THEAETETUS: Indeed, Socrates, I do not know how to prove the one any more than the other, for in both cases the facts precisely correspond; - and there is no difficulty in supposing that during all this discussion we have been talking to one another in a dream; and when in a dream we seem to be narrating dreams, the resemblance of the two states is quite astonishing. SOCRATES: You see, then, that a doubt about the reality of sense is easily raised, since there may even be a doubt whether we are awake or in a dream. And as our time is equally divided between sleeping and waking, in either sphere of existence the soul contends that the thoughts which are present to our minds at the time are true; and during one half of our lives we affirm the truth of the one, and, during the other half, of the other; and are equally confident of both. THEAETETUS: Most true.

SOCRATES: And may not the same be said of madness and other disorders? the difference is only that the times are not equal. THEAETETUS: Certainly. SOCRATES: And is truth or falsehood to be determined by duration of time? THEAETETUS: That would be in many ways ridiculous. SOCRATES: But can you certainly determine by any other means which of these opinions is true? THEAETETUS: I do not think that I can. SOCRATES: Listen, then, to a statement of the other side of the argument, which is made by the champions of appearance. They would say, as I imagine - Can that which is wholly other than something, have the same quality as that from which it differs? and observe, Theaetetus, that the word 'other' means not 'partially,' but 'wholly other.' THEAETETUS: Certainly, putting the question as you do, that which is wholly other cannot either potentially or in any other way be the same. SOCRATES: And must therefore be admitted to be unlike? THEAETETUS: True. SOCRATES: If, then, anything happens to become like or unlike itself or another, when it becomes like we call it the same - when unlike, other? THEAETETUS: Certainly. SOCRATES: Were we not saying that there are agents many and infinite, and patients many and infinite? THEAETETUS: Yes.

SOCRATES: And also that different combinations will produce results which are not the same, but different? THEAETETUS: Certainly. SOCRATES: Let us take you and me, or anything as an example: - There is Socrates in health, and Socrates sick - Are they like or unlike? THEAETETUS: You mean to compare Socrates in health as a whole, and Socrates in sickness as a whole? SOCRATES: Exactly; that is my meaning. THEAETETUS: I answer, they are unlike. SOCRATES: And if unlike, they are other? THEAETETUS: Certainly. SOCRATES: And would you not say the same of Socrates sleeping and waking, or in any of the states which we were mentioning? THEAETETUS: I should. SOCRATES: All agents have a different patient in Socrates, accordingly as he is well or ill. THEAETETUS: Of course. SOCRATES: And I who am the patient, and that which is the agent, will produce something different in each of the two cases? THEAETETUS: Certainly. SOCRATES: The wine which I drink when I am in health, appears sweet and pleasant to me? THEAETETUS: True.

SOCRATES: For, as has been already acknowledged, the patient and agent meet together and produce sweetness and a perception of sweetness, which are in simultaneous motion, and the perception which comes from the patient makes the tongue percipient, and the quality of sweetness which arises out of and is moving about the wine, makes the wine both to be and to appear sweet to the healthy tongue. THEAETETUS: Certainly; that has been already acknowledged. SOCRATES: But when I am sick, the wine really acts upon another and a different person? THEAETETUS: Yes. SOCRATES: The combination of the draught of wine, and the Socrates who is sick, produces quite another result; which is the sensation of bitterness in the tongue, and the motion and creation of bitterness in and about the wine, which becomes not bitterness but something bitter; as I myself become not perception but percipient? THEAETETUS: True. SOCRATES: There is no other object of which I shall ever have the same perception, for another object would give another perception, and would make the percipient other and different; nor can that object which affects me, meeting another subject, produce the same, or become similar, for that too would produce another result from another subject, and become different. THEAETETUS: True.

SOCRATES: Neither can I by myself, have this sensation, nor the object by itself, this quality. THEAETETUS: Certainly not. SOCRATES: When I perceive I must become percipient of something - there can be no such thing as perceiving and perceiving nothing; the object, whether it become sweet, bitter, or of any other quality, must have relation to a percipient; nothing can become sweet which is sweet to no one. THEAETETUS: Certainly not. SOCRATES: Then the inference is, that we (the agent and patient) are or become in relation to one another; there is a law which binds us one to the other, but not to any other existence, nor each of us to himself; and therefore we can only be bound to one another; so that whether a person says that a thing is or becomes, he must say that it is or becomes to or of or in relation to something else; but he must not say or allow any one else to say that anything is or becomes absolutely: - such is our conclusion. THEAETETUS: Very true, Socrates. SOCRATES: Then, if that which acts upon me has relation to me and to no other, I and no other am the percipient of it? THEAETETUS: Of course.

SOCRATES: Then my perception is true to me, being inseparable from my own being; and, as Protagoras says, to myself I am judge of what is and what is not to me. THEAETETUS: I suppose so. SOCRATES: How then, if I never err, and if my mind never trips in the conception of being or becoming, can I fail of knowing that which I perceive? THEAETETUS: You cannot. SOCRATES: Then you were quite right in affirming that knowledge is only perception; and the meaning turns out to be the same, whether with Homer and Heracleitus, and all that company, you say that all is motion and flux, or with the great sage Protagoras, that man is the measure of all things; or with Theaetetus, that, given these premises, perception is knowledge. Am I not right, Theaetetus, and is not this your new-born child, of which I have delivered you? What say you? THEAETETUS: I cannot but agree, Socrates.

SOCRATES: Then this is the child, however he may turn out, which you and I have with difficulty brought into the world. And now that he is born, we must run round the hearth with him, and see whether he is worth rearing, or is only a wind-egg and a sham. Is he to be reared in any case, and not exposed? or will you bear to see him rejected, and not get into a passion if I take away your first-born? THEODORUS: Theaetetus will not be angry, for he is very good-natured. But tell me, Socrates, in heaven's name, is this, after all, not the truth? SOCRATES: You, Theodorus, are a lover of theories, and now you innocently fancy that I am a bag full of them, and can easily pull one out which will overthrow its predecessor. But you do not see that in reality none of these theories come from me; they all come from him who talks with me. I only know just enough to extract them from the wisdom of another, and to receive them in a spirit of fairness. And now I shall say nothing myself, but shall endeavour to elicit something from our young friend. THEODORUS: Do as you say, Socrates; you are quite right.

SOCRATES: I am charmed with his doctrine, that what appears is to each one, but I wonder that he did not begin his book on Truth with a declaration that a pig or a dog-faced baboon, or some other yet stranger monster which has sensation, is the measure of all things; then he might have shown a magnificent contempt for our opinion of him by informing us at the outset that while we were reverencing him like a God for his wisdom he was no better than a tadpole, not to speak of his fellow-men - would not this have produced an overpowering effect? For if truth is only sensation, and no man can discern another's feelings better than he, or has any superior right to determine whether his opinion is true or false, but each, as we have several times repeated, is to himself the sole judge, and everything that he judges is true and right, why, my friend, should Protagoras be preferred to the place of wisdom and instruction, and deserve to be well paid, and we poor ignoramuses have to go to him, if each one is the measure of his own wisdom? Must he not be talking 'ad captandum' in all this? I say nothing of the ridiculous predicament in which my own midwifery and the whole art of dialectic is placed; for the attempt to supervise or refute the notions or opinions of others would be a tedious and enormous piece of folly, if to each man his own are right; and this must be the case if Protagoras' Truth is the real truth, and the philosopher is not merely amusing himself by giving oracles out of the shrine of his book.

THEODORUS: He was a friend of mine, Socrates, as you were saying, and therefore I cannot have him refuted by my lips, nor can I oppose you when I agree with you; please, then, to take Theaetetus again; he seemed to answer very nicely. SOCRATES: If you were to go into a Lacedaemonian palestra, Theodorus, would you have a right to look on at the naked wrestlers, some of them making a poor figure, if you did not strip and give them an opportunity of judging of your own person? THEODORUS: Why not, Socrates, if they would allow me, as I think you will, in consideration of my age and stiffness; let some more supple youth try a fall with you, and do not drag me into the gymnasium. SOCRATES: Your will is my will, Theodorus, as the proverbial philosophers say, and therefore I will return to the sage Theaetetus: Tell me, Theaetetus, in reference to what I was saying, are you not lost in wonder, like myself, when you find that all of a sudden you are raised to the level of the wisest of men, or indeed of the gods? - for you would assume the measure of Protagoras to apply to the gods as well as men?

THEAETETUS: Certainly I should, and I confess to you that I am lost in wonder. At first hearing, I was quite satisfied with the doctrine, that whatever appears is to each one, but now the face of things has changed. SOCRATES: Why, my dear boy, you are young, and therefore your ear is quickly caught and your mind influenced by popular arguments. Protagoras, or some one speaking on his behalf, will doubtless say in reply, - Good people, young and old, you meet and harangue, and bring in the gods, whose existence or non-existence I banish from writing and speech, or you talk about the reason of man being degraded to the level of the brutes, which is a telling argument with the multitude, but not one word of proof or demonstration do you offer. All is probability with you, and yet surely you and Theodorus had better reflect whether you are disposed to admit of probability and figures of speech in matters of such importance. He or any other mathematician who argued from probabilities and likelihoods in geometry, would not be worth an ace. THEAETETUS: But neither you nor we, Socrates, would be satisfied with such arguments. SOCRATES: Then you and Theodorus mean to say that we must look at the matter in some other way?

THEAETETUS: Yes, in quite another way. SOCRATES: And the way will be to ask whether perception is or is not the same as knowledge; for this was the real point of our argument, and with a view to this we raised (did we not?) those many strange questions. THEAETETUS: Certainly. SOCRATES: Shall we say that we know every thing which we see and hear? for example, shall we say that not having learned, we do not hear the language of foreigners when they speak to us? or shall we say that we not only hear, but know what they are saying? Or again, if we see letters which we do not understand, shall we say that we do not see them? or shall we aver that, seeing them, we must know them? THEAETETUS: We shall say, Socrates, that we know what we actually see and hear of them - that is to say, we see and know the figure and colour of the letters, and we hear and know the elevation or depression of the sound of them; but we do not perceive by sight and hearing, or know, that which grammarians and interpreters teach about them.

SOCRATES: But we must say so, if the previous argument is to be maintained. THEAETETUS: What do you mean? I am not quite sure that I understand you, though I have a strong suspicion that you are right. SOCRATES: As thus: he who sees knows, as we say, that which he sees; for perception and sight and knowledge are admitted to be the same. THEAETETUS: Certainly. SOCRATES: But he who saw, and has knowledge of that which he saw, remembers, when he closes his eyes, that which he no longer sees. THEAETETUS: True. SOCRATES: And seeing is knowing, and therefore not-seeing is not-knowing? THEAETETUS: Very true. SOCRATES: Then the inference is, that a man may have attained the knowledge of something, which he may remember and yet not know, because he does not see; and this has been affirmed by us to be a monstrous supposition. THEAETETUS: Most true. SOCRATES: Thus, then, the assertion that knowledge and perception are one, involves a manifest impossibility? THEAETETUS: Yes. SOCRATES: Then they must be distinguished? THEAETETUS: I suppose that they must. SOCRATES: Once more we shall have to begin, and ask 'What is knowledge?' and yet, Theaetetus, what are we going to do? THEAETETUS: About what?

SOCRATES: Like a good-for-nothing cock, without having won the victory, we walk away from the argument and crow. THEAETETUS: How do you mean? SOCRATES: After the manner of disputers (Lys.; Phaedo; Republic), we were satisfied with mere verbal consistency, and were well pleased if in this way we could gain an advantage. Although professing not to be mere Eristics, but philosophers, I suspect that we have unconsciously fallen into the error of that ingenious class of persons. THEAETETUS: I do not as yet understand you. SOCRATES: Then I will try to explain myself: just now we asked the question, whether a man who had learned and remembered could fail to know, and we showed that a person who had seen might remember when he had his eyes shut and could not see, and then he would at the same time remember and not know. But this was an impossibility. And so the Protagorean fable came to nought, and yours also, who maintained that knowledge is the same as perception. THEAETETUS: True.