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By Plato

Translated by Benjamin Jowett

Persons of the Dialogue

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. 

Euc. But I was not in the city. 

Terp. Where then? 

Euc. As I was going down to the harbour, I met Theaetetus-he was being
carried up to Athens from the army at Corinth. 

Terp. Was he alive or dead? 

Euc. 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. 

Terp. The dysentery, you mean? 

Euc. Yes. 

Terp. Alas! what a loss he will be! 

Euc. Yes, Terpsion, he is a noble fellow; only to-day I heard some
people highly praising his behaviour in this very battle.

Terp. No wonder; I should rather be surprised at hearing anything
else of him. But why did he go on, instead of stopping at Megara?

Euc. 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. 

Terp. The prophecy has certainly been fulfilled; but what was the
conversation? can you tell me? 

Euc. 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. 

Terp. 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. 

Euc. 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. 

Terp. Very good. 

Euc. 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.

Terp. Quite right, Euclid. 

Euc. 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 anyone 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. 

Soc. That is good news; whose son is he? 

Theod. 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 towards us. Look and see whether you know

Soc. 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. 

Theod. Theaetetus, Socrates, is his name; but I rather think that
the property disappeared in the hands of trustees; notwithstanding
which he is wonderfully liberal. 

Soc. He must be a fine fellow; tell him to come and sit by me.

Theod. I will. Come hither, Theaetetus, and sit by Socrates.

Soc. 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. 

Soc. And if we found that he was, we should take his word; and if
not, not? 

Theaet. True. 

Soc. 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? 

Theaet. Certainly we should. 

Soc. And is Theodorus a painter? 

Theaet. I never heard that he was. 

Soc. Is he a geometrician? 

Theaet. Of course he is, Socrates. 

Soc. And is he an astronomer and calculator and musician, and in general
an educated man? 

Theaet. I think so. 

Soc. 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. 

Theaet. I should say not. 

Soc. 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

Theaet. Very true, Socrates. 

Soc. 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. 

Theaet. I am glad to hear it, Socrates; but what if he was only in

Soc. 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. 

Theaet. I suppose I must, if you wish it. 

Soc. In the first place, I should like to ask what you learn of Theodorus:
something of geometry, perhaps? 

Theaet. Yes. 

Soc. And astronomy and harmony and calculation? 

Theaet. I do my best. 

Soc. 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?"

Theaet. Of course. 

Soc. And by wisdom the wise are wise? 

Theaet. Yes. 

Soc. And is that different in any way from knowledge? 

Theaet. What? 

Soc. Wisdom; are not men wise in that which they know? 

Theaet. Certainly they are. 

Soc. Then wisdom and knowledge are the same? 

Theaet. Yes. 

Soc. 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. 

Theod. 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. 

Soc. 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. 

Theaet. Well, Socrates, I will answer as you and he bid me; and if
make a mistake, you will doubtless correct me. 

Soc. We will, if we can. 

Theaet. 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. 

Soc. 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. 

Theaet. What do you mean, Socrates? 

Soc. 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? 

Theaet. Just so. 

Soc. And when you speak of carpentering, you mean the art of making
wooden implements? 

Theaet. I do. 

Soc. In both cases you define the subject matter of each of the two

Theaet. True. 

Soc. But that, Theaetetus, was not the point of my question: we wanted
to know not the subjects, nor yet the number of the arts or sciences,
for we were not going to count them, but we wanted to know the nature
of knowledge in the abstract. Am I not right? 

Theaet. Perfectly right. 

Soc. Let me offer an illustration: Suppose that a person were to ask
about some very trivial and obvious thing-for example, What is clay?
and we were to reply, that there is a clay of potters, there is a
clay of oven-makers, there is a clay of brick-makers; would not the
answer be ridiculous? 

Theaet. Truly. 

Soc. In the first place, there would be an absurdity in assuming that
he who asked the question would understand from our answer the nature
of "clay," merely because we added "of the image-makers," or of any
other workers. How can a man understand the name of anything, when
he does not know the nature of it? 

Theaet. He cannot. 

Soc. Then he who does not know what science or knowledge is, has no
knowledge of the art or science of making shoes? 

Theaet. None. 

Soc. Nor of any other science? 

Theaet. No. 

Soc. 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."

Theaet. True. 

Soc. Moreover, he might answer shortly and simply, but he makes an
enormous circuit. For example, when asked about the day, he might
have said simply, that clay is moistened earth-what sort of clay is
not to the point. 

Theaet. 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.

Soc. What was that, Theaetetus? 

Theaet. 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. 

Soc. And did you find such a class? 

Theaet. I think that we did; but I should like to have your opinion.

Soc. Let me hear. 

Theaet. 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. 

Soc. Very good. 

Theaet. 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.

Soc. Capital; and what followed? 

Theaet. 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 linearmeasurement,
but in the value of the superficial content of their squares; and
the same about solids. 

Soc. Excellent, my boys; I think that you fully justify the praises
of Theodorus, and that he will not be found guilty of false witness.

Theaet. 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. 

Soc. 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? 

Theaet. Certainly not. 

Soc. 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? 

Theaet. By heaven, they should be the top of all perfection!

Soc. 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. 

Theaet. I am eager enough, Socrates, if that would bring to light
the truth. 

Soc. 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.

Theaet. 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. 

Soc. These are the pangs of labour, my dear Theaetetus; you have something
within you which you are bringing to the birth. 

Theaet. I do not know, Socrates; I only say what I feel.

Soc. And have you never heard, simpleton, that I am the son of a midwife,
brave and burly, whose name was Phaenarete? 

Theaet. Yes, I have. 

Soc. And that I myself practise midwifery? 

Theaet. No, never. 

Soc. 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?

Theaet. Yes. 

Soc. Shall I tell you the reason? 

Theaet. By all means. 

Soc. Bear in mind the whole business of the mid-wives, 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. 

Theaet. Yes; I know. 

Soc. 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 mid-wives, 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.

Theaet. I dare say. 

Soc. And I dare say too, or rather I am absolutely certain, that the
mid-wives know better than others who is pregnant and who is not?

Theaet. Very true. 

Soc. 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. 

Theaet. They can. 

Soc. 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? 

Theaet. No, never. 

Soc. 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. 

Theaet. Yes, the same art. 

Soc. And do you suppose that with women the case is otherwise?

Theaet. I should think not. 

Soc. Certainly not; but mid-wives 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

Theaet. Clearly. 

Soc. Such are the mid-wives, 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? 

Theaet. Indeed I should. 

Soc. 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 mid-wives, 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 dear 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 good will, 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. 

Theaet. 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.

Soc. 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? 

Theaet. Yes. 

Soc. 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? 

Theaet. O yes, again and again. 

Soc. 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?

Theaet. Yes, he says so. 

Soc. 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?

Theaet. Quite true. 

Soc. 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? 

Theaet. I suppose the last. 

Soc. Then it must appear so to each of them? 

Theaet. Yes. 

Soc. And "appears to him" means the same as "he perceives."

Theaet. True. 

Soc. 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? 

Theaet. Yes. 

Soc. Then perception is always of existence, and being the same as
knowledge is unerring? 

Theaet. Clearly. 

Soc. 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 secret to his own

Theaet. What do you mean, Socrates? 

Soc. 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? 

Theaet. I think so. 

Soc. And who could take up arms against such a great army having Homer
for its general, and not appear ridiculous? 

Theaet. Who indeed, Socrates? 

Soc. 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 friction, which is a kind of motion;-is not
this the origin of fire? 

Theaet. It is. 

Soc. And the race of animals is generated in the same way?

Theaet. Certainly. 

Soc. And is not the bodily habit spoiled by rest and idleness, but
preserved for a long time by motion and exercise? 

Theaet. True. 

Soc. 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?

Theaet. True. 

Soc. Then motion is a good, and rest an evil, to the soul as well
as to the body? 

Theaet. Clearly. 

Soc. 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. 

Theaet. I believe, Socrates, that you have truly explained his meaning.

Soc. 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.

Theaet. Then what is colour? 

Soc. 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? 

Theaet. Far from it. 

Soc. 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? 

Theaet. The latter. 

Soc. 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. 

Theaet. How? and of what sort do you mean? 

Soc. 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? 

Theaet. Very true. 

Soc. 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? 

Theaet. 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. 

Soc. 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. 

Theaet. Very true. 

Soc. 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. 

Theaet. Yes, that would be my desire. 

Soc. 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? 

Theaet. Yes. 

Soc. Secondly, that without addition or subtraction there is no increase
or diminution of anything, but only equality. 

Theaet. Quite true. 

Soc. Thirdly, that what was not before cannot be afterwards, without
becoming and having become. 

Theaet. Yes, truly. 

Soc. 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.

Theaet. 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.

Soc. 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? 

Theaet. Not as yet. 

Soc. Then you will be obliged to me if I help you to unearth the hidden
"truth" of a famous man or school. 

Theaet. To be sure, I shall be very much obliged. 

Soc. 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

Theaet. Yes, indeed, Socrates, they are very hard and impenetrable

Soc. 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? 

Theaet. Indeed I do not. 

Soc. 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 colour,ed 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 aggregates as are expressed in the word "man," or "stone," or
any name of animal or of a class. O Theaetetus, are not these speculations
sweet as honey? And do you not like the taste of them in the mouth?

Theaet. 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. 

Soc. 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. 

Theaet. Ask me. 

Soc. 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? 

Theaet. 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. Soc.
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. 

Theaet. Very true, Socrates. 

Soc. But then, my boy, how can any one contend that knowledge is perception,
or that to every man what appears is? 

Theaet. 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. 

Soc. Do you see another question which can be raised about these phenomena,
notably about dreaming and waking? 

Theaet. What question? 

Soc. 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? 

Theaet. 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. 

Soc. 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.

Theaet. Most true. 

Soc. And may not the same be said of madness and other disorders?
the difference is only that the times are not equal. 

Theaet. Certainly. 

Soc. And is truth or falsehood to be determined by duration of time?

Theaet. That would be in many ways ridiculous. 

Soc. But can you certainly determine: by any other means which of
these opinions is true? 

Theaet. I do not think that I can. 

Soc. 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."

Theaet. Certainly, putting the question as you do, that which is wholly
other cannot either potentially or in any other way be the same.

Soc. And must therefore be admitted to be unlike? 

Theaet. True. 

Soc. If, then, anything happens to become like or unlike itself or
another, when it becomes like we call it the same-when unlike, other?

Theaet. Certainly. 

Soc. Were we not saying that there. are agents many and infinite,
and patients many and infinite? 

Theaet. Yes. 

Soc. And also that different combinations will produce results which
are not the same, but different? 

Theaet. Certainly. 

Soc. Let us take you and me, or anything as an example:-There is Socrates
in health, and Socrates sick-Are they like or unlike? 

Theaet. You mean to, compare Socrates in health as a whole, and Socrates
in sickness as a whole? 

Soc. Exactly; that is my meaning. 

Theaet. I answer, they are unlike. 

Soc. And if unlike, they are other? 

Theaet. Certainly. 

Soc. And would you not say the same of Socrates sleeping and waking,
or in any of the states which we were mentioning? 

Theaet. I should. 

Soc. All agents have a different patient in Socrates, accordingly
as he is well or ill. 

Theaet. Of course. 

Soc. And I who am the patient, and that which is the agent, will produce
something different in each of the two cases? 

Theaet. Certainly. 

Soc. The wine which I drink when I am in health, appears sweet and
pleasant to me? 

Theaet. True. 

Soc. 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. 

Theaet. Certainly; that has been already acknowledged. 

Soc. But when I am sick, the wine really acts upon another and a different

Theaet. Yes. 

Soc. 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 but percipient? 

Theaet. True. 

Soc. 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 perception 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. 

Theaet. True. 

Soc. Neither can by myself, have this sensation, nor the object by
itself, this quality. 

Theaet. Certainly not. 

Soc. 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. 

Theaet. Certainly not. 

Soc. 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. 

Theaet. Very true, Socrates. 

Soc. Then, if that which acts upon me has relation to me and to no
other, I and no other am the percipient of it? 

Theaet. Of course. 

Soc. 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. 

Theaet. I suppose so. 

Soc. 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?

Theaet. You cannot. 

Soc. 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 newborn
child, of which I have delivered you? What say you? 

Theaet. I cannot but agree, Socrates. 

Soc. 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?

Theod. 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

Soc. 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. 

Theod. Do as you say, Socrates; you are quite right. 

Soc. Shall I tell you, Theodorus, what amazes me in your acquaintance

Theod. What is it? 

Soc. 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 over-powering 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. 

Theod. 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. 

Soc. 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? 

Theod. 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.

Soc. 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? 

Theaet. 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

Soc. 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 of 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. 

Theaet. But neither you nor we, Socrates, would be satisfied with
such arguments. 

Soc. Then you and Theodorus mean to say that we must look at the matter
in some other way? 

Theaet. Yes, in quite another way. 

Soc. 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.

Theaet. Certainly. 

Soc. 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?

Theaet. 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.

Soc. Capital, Theaetetus; and about this there shall be no dispute,
because I want you to grow; but there is another difficulty coming,
which you will also have to repulse. 

Theaet. What is it? 

Soc. Some one will say, Can a man who has ever known anything, and
still has and preserves a memory of that which he knows, not know
that which he remembers at the time when he remembers? I have, I fear,
a tedious way of putting a simple question, which is only, whether
a man who has learned, and remembers, can fail to know? 

Theaet. Impossible, Socrates; the supposition is monstrous.

Soc. Am I talking nonsense, then? Think: is not seeing perceiving,
and is not sight perception? 

Theaet. True. 

Soc. And if our recent definition holds, every man knows that which
he has seen? 

Theaet. Yes. 

Soc. And you would admit that there is such a thing as memory?

Theaet. Yes. 

Soc. And is memory of something or of nothing? 

Theaet. Of something, surely. 

Soc. Of things learned and perceived, that is? 

Theaet. Certainly. 

Soc. Often a man remembers that which he has seen? 

Theaet. True. 

Soc. And if he closed his eyes, would he forget? 

Theaet. Who, Socrates, would dare to say so? 

Soc. But we must say so, if the previous argument is to be maintained.

Theaet. What do you mean? I am not quite sure that I understand you,
though I have a strong suspicion that you are right. 

Soc. 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.

Theaet. Certainly. 

Soc. But he who saw, and has knowledge of that which he saw, remembers,
when he closes his eyes, that which he no longer sees. 

Theaet. True. 

Soc. And seeing is knowing, and therefore not-seeing is not-knowing?

Theaet. Very true. 

Soc. 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.

Theaet. Most true. 

Soc. Thus, then, the assertion that knowledge and perception are one,
involves a manifest impossibility? 

Theaet. Yes. 

Soc. Then they must be distinguished? 

Theaet. I suppose that they must. 

Soc. Once more we shall have to begin, and ask "What is knowledge?"
and yet, Theaetetus, what are we going to do? 

Theaet. About what? 

Soc. Like a good-for-nothing cock, without having won the victory,
we walk away from the argument and crow. 

Theaet. How do you mean? 

Soc. After the manner of disputers, 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. 

Theaet. I do not as yet understand you. 

Soc. 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. 

Theaet. True. 

Soc. And yet, my friend, I rather suspect that the result would have
been different if Protagoras, who was the father of the first of the
two-brats, had been alive; he would have had a great deal to say on
their behalf. But he is dead, and we insult over his orphan child;
and even the guardians whom he left, and of whom our friend Theodorus
is one, are unwilling to give any help, and therefore I suppose that
must take up his cause myself, and see justice done? 

Theod. Not I, Socrates, but rather Callias, the son of Hipponicus,
is guardian of his orphans. I was too soon diverted from the abstractions
of dialectic to geometry. Nevertheless, I shall be grateful to you
if you assist him. 

Soc. Very good, Theodorus; you shall see how I will come to the rescue.
If a person does not attend to the meaning of terms as they are commonly
used in argument, he may be involved even in greater paradoxes than
these. Shall I explain this matter to you or to Theaetetus?

Theod. To both of us, and let the younger answer; he will incur less
disgrace if he is discomfited. 

Soc. Then now let me ask the awful question, which is this:-Can a
man know and also not know that which he knows? 

Theod. How shall we answer, Theaetetus? 

Theaet. He cannot, I should say. 

Soc. He can, if you maintain that seeing is knowing. When you are
imprisoned in a well, as the saying is, and the self-assured adversary
closes one of your eyes with his hand, and asks whether you can see
his cloak with the eye which he has closed, how will you answer the
inevitable man? 

Theaet. I should answer, "Not with that eye but with the other."

Soc. Then you see and do not see the same thing at the same time.

Theaet. Yes, in a certain sense. 

Soc. None of that, he will reply; I do not ask or bid you answer in
what sense you know, but only whether you know that which you do not
know. You have been proved to see that which you do not see; and you
have already admitted that seeing is knowing, and that not-seeing
is not-knowing: I leave you to draw the inference. 

Theaet. Yes, the inference is the contradictory of my assertion.

Soc. Yes, my marvel, and there might have been yet worse things in
store for you, if an opponent had gone on to ask whether you can have
a sharp and also a dull knowledge, and whether you can know near,
but not at a distance, or know the same thing with more or less intensity,
and so on without end. Such questions might have been put to you by
a light-armed mercenary, who argued for pay. He would have lain in
wait for you, and when you took up the position, that sense is knowledge,
he would have made an assault upon hearing, smelling, and the other
senses;-he would have shown you no mercy; and while you were lost
in envy and admiration of his wisdom, he would have got you into his
net, out of which you would not have escaped until you had come to
an understanding about the sum to be paid for your release. Well,
you ask, and how will Protagoras reinforce his position? Shall I answer
for him? 

Theaet. By all means. 

Soc. He will repeat all those things which we have been urging on
his behalf, and then he will close with us in disdain, and say:-The
worthy Socrates asked a little boy, whether the same man could remember
and not know the same thing, and the boy said No, because he was frightened,
and could not see what was coming, and then Socrates made fun of poor
me. The truth is, O slatternly Socrates, that when you ask questions
about any assertion of mine, and the person asked is found tripping,
if he has answered as I should have answered, then I am refuted, but
if he answers something else, then he is refuted and not I. For do
you really suppose that any one would admit the memory which a man
has of an impression which has passed away to be the same with that
which he experienced at the time? Assuredly not. Or would he hesitate
to acknowledge that the same man may know and not know the same thing?
Or, if he is afraid of making this admission, would he ever grant
that one who has become unlike is the same as before he became unlike?
Or would he admit that a man is one at all, and not rather many and
infinite as the changes which take place in him? I speak by the card
in order to avoid entanglements of words. But, O my good sir, he would
say, come to the argument in a more generous spirit; and either show,
if you can, that our sensations are not relative and individual, or,
if you admit them to be so, prove that this does not involve the consequence
that the appearance becomes, or, if you will have the word, is, to
the individual only. As to your talk about pigs and baboons, you are
yourself behaving like a pig, and you teach your hearers to make sport
of my writings in the same ignorant manner; but this is not to your
credit. For I declare that the truth is as I have written, and that
each of us is a measure of existence and of non-existence. Yet one
man may be a thousand times better than another in proportion as different
things are and appear to him. 

And I am far from saying that wisdom and the wise man have no existence;
but I say that the wise man is he who makes the evils which appear
and are to a man, into goods which are and appear to him. And I would
beg you not to my words in the letter, but to take the meaning of
them as I will explain them. Remember what has been already said,-that
to the sick man his food appears to be and is bitter, and to the man
in health the opposite of bitter. Now I cannot conceive that one of
these men can be or ought to be made wiser than the other: nor can
you assert that the sick man because he has one impression is foolish,
and the healthy man because he has another is wise; but the one state
requires to be changed into the other, the worse into the better.
As in education, a change of state has to be effected, and the sophist
accomplishes by words the change which the physician works by the
aid of drugs. Not that any one ever made another think truly, who
previously thought falsely. For no one can think what is not, or think
anything different from that which he feels; and this is always true.
But as the inferior habit of mind has thoughts of kindred nature,
so I conceive that a good mind causes men to have good thoughts; and
these which the inexperienced call true, I maintain to be only better,
and not truer than others. And, O my dear Socrates, I do not call
wise men tadpoles: far from it; I say that they are the physicians
of the human body, and the husbandmen of plants-for the husbandmen
also take away the evil and disordered sensations of plants, and infuse
into them good and healthy sensations-aye and true ones; and the wise
and good rhetoricians make the good instead of the evil to seem just
to states; for whatever appears to a state to be just and fair, so
long as it is regarded as such, is just and fair to it; but the teacher
of wisdom causes the good to take the place of the evil, both in appearance
and in reality. And in like manner the Sophist who is able to train
his pupils in this spirit is a wise man, and deserves to be well paid
by them. And so one man is wiser than another; and no one thinks falsely,
and you, whether you will or not, must endure to be a measure. On
these foundations the argument stands firm, which you, Socrates, may,
if you please, overthrow by an opposite argument, or if you like you
may put questions to me-a method to which no intelligent person will
object, quite the reverse. But I must beg you to put fair questions:
for there is great inconsistency in saying that you have a zeal for
virtue, and then always behaving unfairly in argument. The unfairness
of which I complain is that you do not distinguish between mere disputation
and dialectic: the disputer may trip up his opponent as often as he
likes, and make fun; but the dialectician will be in earnest, and
only correct his adversary when necessary, telling him the errors
into which he has fallen through his own fault, or that of the company
which he has previously kept. If you do so, your adversary will lay
the blame of his own confusion and perplexity on himself, and not
on you; will follow and love you, and will hate himself, and escape
from himself into philosophy, in order that he may become different
from what he was. But the other mode of arguing, which is practised
by the many, will have just the opposite effect upon him; and as he
grows older, instead of turning philosopher, he will come to hate
philosophy. I would recommend you, therefore, as I said before, not
to encourage yourself in this polemical and controversial temper,
but to find out, in a friendly and congenial spirit, what we really
mean when we say that all things are in motion, and that to every
individual and state what appears, is. In this manner you will consider
whether knowledge and sensation are the same or different, but you
will not argue, as you were just now doing, from the customary use
of names and words, which the vulgar pervert in all sorts of ways,
causing infinite perplexity to one another. Such, Theodorus, is the
very slight help which I am able to offer to your old friend; had
he been living, he would have helped himself in a far more gloriose

Theod. You are jesting, Socrates; indeed, your defence of him has
been most valorous. 

Soc. Thank you, friend; and I hope that you observed Protagoras bidding
us be serious, as the text, "Man is the measure of all things," was
a solemn one; and he reproached us with making a boy the medium of
discourse, and said that the boy's timidity was made to tell against
his argument; he also declared that we made a joke of him.

Theod. How could I fail to observe all that, Socrates? 

Soc. Well, and shall we do as he says? 

Theod. By all means. 

Soc. But if his wishes are to be regarded, you and I must take up
the argument, and in all seriousness, and ask and answer one another,
for you see that the rest of us are nothing but boys. In no other
way can we escape the imputation, that in our fresh analysis of his
thesis we are making fun with boys. 

Theod. Well, but is not Theaetetus better able to follow a philosophical
enquiry than a great many men who have long beards? 

Soc. Yes, Theodorus, but not better than you; and therefore please
not to imagine that I am to defend by every means in my power your
departed friend; and that you are to defend nothing and nobody. At
any rate, my good man, do not sheer off until we know whether you
are a true measure of diagrams, or whether all men are equally measures
and sufficient for themselves in astronomy and geometry, and the other
branches of knowledge in which you are supposed to excel them.

Theod. He who is sitting by you, Socrates, will not easily avoid being
drawn into an argument; and when I said just now that you would excuse
me, and not, like the Lacedaemonians, compel me to strip and fight,
I was talking nonsense-I should rather compare you to Scirrhon, who
threw travellers from the rocks; for the Lacedaemonian rule is "strip
or depart," but you seem to go about your work more after the fashion
of Antaeus: you will not allow any one who approaches you to depart
until you have stripped him, and he has been compelled to try a fall
with you in argument. 

Soc. There, Theodorus, you have hit off precisely the nature of my
complaint; but I am even more pugnacious than the giants of old, for
I have met with no end of heroes; many a Heracles, many a Theseus,
mighty in words, has broken my head; nevertheless I am always at this
rough exercise, which inspires me like a passion. Please, then, to
try a fall with me, whereby you will do yourself good as well as me.

Theod. I consent; lead me whither you will, for I know that you are
like destiny; no man can escape from any argument which you may weave
for him. But I am not disposed to go further than you suggest.

Soc. Once will be enough; and now take particular care that we do
not again unwittingly expose ourselves to the reproach of talking

Theod. I will do my best to avoid that error. 

Soc. In the first place, let us return to our old objection, and see
whether we were right in blaming and taking offence at Protagoras
on the ground that he assumed all to be equal and sufficient in wisdom;
although he admitted that there was a better and worse, and that in
respect of this, some who as he said were the wise excelled others.

Theod. Very true. 

Soc. Had Protagoras been living and answered for himself, instead
of our answering for him, there would have been no need of our reviewing
or reinforcing the argument. But as he is not here, and some one may
accuse us of speaking without authority on his behalf, had we not
better come to a clearer agreement about his meaning, for a great
deal may be at stake? 

Theod. True. 

Soc. Then let us obtain, not through any third person, but from his
own statement and in the fewest words possible, the basis of agreement.

Theod. In what way? 

Soc. In this way:-His words are, "What seems to a man, is to him."

Theod. Yes, so he says. 

Soc. And are not we, Protagoras, uttering the opinion of man, or rather
of all mankind, when we say that every one thinks himself wiser than
other men in some things, and their inferior in others? In the hour
of danger, when they are in perils of war, or of the sea, or of sickness,
do they not look up to their commanders as if they were gods, and
expect salvation from them, only because they excel them in knowledge?
Is not the world full of men in their several employments, who are
looking for teachers and rulers of themselves and of the animals?
and there are plenty who think that they are able to teach and able
to rule. Now, in all this is implied that ignorance and wisdom exist
among them, least in their own opinion. 

Theod. Certainly. 

Soc. And wisdom is assumed by them to be true thought, and ignorance
to be false opinion. 

Theod. Exactly. 

Soc. How then, Protagoras, would you have us treat the argument? Shall
we say that the opinions of men are always true, or sometimes true
and sometimes false? In either case, the result is the same, and their
opinions are not always true, but sometimes true and sometimes false.
For tell me, Theodorus, do you suppose that you yourself, or any other
follower of Protagoras, would contend that no one deems another ignorant
or mistaken in his opinion? 

Theod. The thing is incredible, Socrates. 

Soc. And yet that absurdity is necessarily involved in the thesis
which declares man to be the measure of all things. 

Theod. How so? 

Soc. Why, suppose that you determine in your own mind something to
be true, and declare your opinion to me; let us assume, as he argues,
that this is true to you. Now, if so, you must either say that the
rest of us are not the judges of this opinion or judgment of yours,
or that we judge you always to have a true opinion: But are there
not thousands upon thousands who, whenever you form a judgment, take
up arms against you and are of an opposite judgment and opinion, deeming
that you judge falsely? 

Theod. Yes, indeed, Socrates, thousands and tens of thousands, as
Homer says, who give me a world of trouble. 

Soc. Well, but are we to assert that what you think is true to you
and false to the ten thousand others? 

Theod. No other inference seems to be possible. 

Soc. And how about Protagoras himself? If neither he nor the multitude
thought, as indeed they do not think, that man is the measure of all
things, must it not follow that the truth of which Protagoras wrote
would be true to no one? But if you suppose that he himself thought
this, and that the multitude does not agree with him, you must begin
by allowing that in whatever proportion the many are more than one,
in that proportion his truth is more untrue than true. 

Theod. That would follow if the truth is supposed to vary with individual

Soc. And the best of the joke is, that he acknowledges the truth of
their opinion who believe his own opinion to be false; for he admits
that the opinions of all men are true. 

Theod. Certainly. 

Soc. And does he not allow that his own opinion is false, if he admits
that the opinion of those who think him false is true? 

Theod. Of course. 

Soc. Whereas the other side do not admit that they speak falsely?

Theod. They do not. 

Soc. And he, as may be inferred from his writings, agrees that this
opinion is also true. 

Theod. Clearly. 

Soc. Then all mankind, beginning with Protagoras, will contend, or
rather, I should say that he will allow, when he concedes that his
adversary has a true opinion-Protagoras, I say, will himself allow
that neither a dog nor any ordinary man is the measure of anything
which he has not learned-am I not right? 

Theod. Yes. 

Soc. And the truth of Protagoras being doubted by all, will be true
neither to himself to any one else? 

Theod. I think, Socrates, that we are running my old friend too hard.

Soc. But do not know that we are going beyond the truth. Doubtless,
as he is older, he may be expected to be wiser than we are. And if
he could only just get his head out of the world below, he would have
overthrown both of us again and again, me for talking nonsense and
you for assenting to me, and have been off and underground in a trice.
But as he is not within call, we must make the best use of our own
faculties, such as they are, and speak out what appears to us to be
true. And one thing which no one will deny is, that there are great
differences in the understandings of men. 

Theod. In that opinion I quite agree. 

Soc. And is there not most likely to be firm ground in the distinction
which we were indicating on behalf of Protagoras, viz., that most
things, and all immediate sensations, such as hot, dry, sweet, are
only such as they appear; if however difference of opinion is to be
allowed at all, surely we must allow it in respect of health or disease?
for every woman, child, or living creature has not such a knowledge
of what conduces to health as to enable them to cure themselves.

Theod. I quite agree. 

Soc. Or again, in politics, while affirming that just and unjust,
honourable and disgraceful, holy and unholy, are in reality to each
state such as the state thinks and makes lawful, and that in determining
these matters no individual or state is wiser than another, still
the followers of Protagoras will not deny that in determining what
is or is not expedient for the community one state is wiser and one
counsellor better that another-they will scarcely venture to maintain,
that what a city enacts in the belief that it is expedient will always
be really expedient. But in the other case, I mean when they speak
of justice and injustice, piety and impiety, they are confident that
in nature these have no existence or essence of their own-the truth
is that which is agreed on at the time of the agreement, and as long
as the agreement lasts; and this is the philosophy of many who do
not altogether go along with Protagoras. Here arises a new question,
Theodorus, which threatens to be more serious than the last.

Theod. Well, Socrates, we have plenty of leisure. 

Soc. That is true, and your remark recalls to my mind an observation
which I have often made, that those who have passed their days in
the pursuit of philosophy are ridiculously at fault when they have
to appear and speak in court. How natural is this! 

Theod. What do you mean? 

Soc. I mean to say, that those who have been trained in philosophy
and liberal pursuits are as unlike those who from their youth upwards
have been knocking about in the courts and such places, as a freeman
is in breeding unlike a slave. 

Theod. In what is the difference seen? 

Soc. In the leisure spoken of by you, which a freeman can always command:
he has his talk, out in peace, and, like ourselves, he wanders at
will from one subject to another, and from a second to a third,-if
the fancy takes him he begins again, as we are doing now, caring not
whether his words are many or few; his only aim is to attain the truth.
But the lawyer is always in a hurry; there is the water of the clepsydra
driving him on, and not allowing him to expatiate at will: and there
is his adversary standing over him, enforcing his rights; the indictment,
which in their phraseology is termed the affidavit, is recited at
the time: and from this he must not deviate. He is a servant, and
is continually disputing about a fellow servant before his master,
who is seated, and has the cause in his hands; the trial is never
about some indifferent matter, but always concerns himself; and often
the race is for his life. The consequence has been, that he has become
keen and shrewd; he has learned how to flatter his master in word
and indulge him in deed; but his soul is small and unrighteous. His
condition, which has been that of a slave from his youth upwards,
has deprived him of growth and uprightness and independence; dangers
and fears, which were too much for his truth and honesty, came upon
him in early years, when the tenderness of youth was unequal to them,
and he has been driven into crooked ways; from the first he has practised
deception and retaliation, and has become stunted and warped. And
so he has passed out of youth into manhood, having no soundness in
him; and is now, as he thinks, a master in wisdom. Such is the lawyer,
Theodorus. Will you have the companion picture of the philosopher,
who is of our brotherhood; or shall we return to the argument? Do
not let us abuse the freedom of digression which we claim.

Theod. Nay, Socrates, not until we have finished what we are about;
for you truly said that we belong to a brotherhood which is free,
and are not the servants of the argument; but the argument is our
servant, and must wait our leisure. Who is our judge? Or where is
the spectator having any right to censure or control us, as he might
the poets? 

Soc. Then, as this is your wish, I will describe the leaders; for
there is no use in talking about the inferior sort. In the first place,
the lords of philosophy have never, from their youth upwards, known
their way to the Agora, or the dicastery, or the council, or any other
political assembly; they neither see nor hear the laws or decrees,
as they are called, of the state written or recited; the eagerness
of political societies in the attainment of office-clubs, and banquets,
and revels, and singing-maidens,-do not enter even into their dreams.
Whether any event has turned out well or ill in the city, what disgrace
may have descended to any one from his ancestors, male or female,
are matters of which the philosopher no more knows than he can tell,
as they say, how many pints are contained in the ocean. Neither is
he conscious of his ignorance. For he does not hold aloof in order;
that he may gain a reputation; but the truth is, that the outer form
of him only is in the city: his mind, disdaining the littlenesses
and nothingnesses of human things, is "flying all abroad" as Pindar
says, measuring earth and heaven and the things which are under and
on the earth and above the heaven, interrogating the whole nature
of each and all in their entirety, but not condescending to anything
which is within reach. 

Theod. What do you mean, Socrates? 

Soc. I will illustrate my meaning, Theodorus, by the jest which the
clever witty Thracian handmaid is said to have made about Thales,
when he fell into a well as he was looking up at the stars. She said,
that he was so eager to know what was going on in heaven, that he
could not see what was before his feet. This is a jest which is equally
applicable to all philosophers. For the philosopher is wholly unacquainted
with his next-door neighbour; he is ignorant, not only of what he
is doing, but he hardly knows whether he is a man or an animal; he
is searching into the essence of man, and busy in enquiring what belongs
to such a nature to do or suffer different from any other;-I think
that you understand me, Theodorus? 

Theod. I do, and what you say is true. 

Soc. And thus, my friend, on every occasion, private as well as public,
as I said at first, when he appears in a law-court, or in any place
in which he has to speak of things which are at his feet and before
his eyes, he is the jest, not only of Thracian handmaids but of the
general herd, tumbling into wells and every sort of disaster through
his inexperience. His awkwardness is fearful, and gives the impression
of imbecility. When he is reviled, he has nothing personal to say
in answer to the civilities of his adversaries, for he knows no scandals
of any one, and they do not interest him; and therefore he is laughed
at for his sheepishness; and when others are being praised and glorified,
in the simplicity of his heart he cannot help going into fits of laughter,
so that he seems to be a downright idiot. When he hears a tyrant or
king eulogized, he fancies that he is listening to the praises of
some keeper of cattle-a swineherd, or shepherd, or perhaps a cowherd,
who is congratulated on the quantity of milk which he squeezes from
them; and he remarks that the creature whom they tend, and out of
whom they squeeze the wealth, is of a less traitable and more insidious
nature. Then, again, he observes that the great man is of necessity
as ill-mannered and uneducated as any shepherd-for he has no leisure,
and he is surrounded by a wall, which is his mountain-pen. Hearing
of enormous landed proprietors of ten thousand acres and more, our
philosopher deems this to be a trifle, because he has been accustomed
to think of the whole earth; and when they sing the, praises of family,
and say that someone is a gentleman because he can show seven generations
of wealthy ancestors, he thinks that their sentiments only betray
a dull and narrow vision in those who utter them, and who are not
educated enough to look at the whole, nor to consider that every man
has had thousands and ten thousands of progenitors, and among them
have been rich and poor, kings and slaves, Hellenes and barbarians,
innumerable. And when people pride themselves on having a pedigree
of twenty-five ancestors, which goes back to Heracles, the son of
Amphitryon, he cannot understand their poverty of ideas. Why are they
unable to calculate that Amphitryon had a twenty-fifth ancestor, who
might have been anybody, and was such as fortune made him and he had
a fiftieth, and so on? He amuses himself with the notion that they
cannot count, and thinks that a little arithmetic would have got rid
of their senseless vanity. Now, in all these cases our philosopher
is derided by the vulgar, partly because he is thought to despise
them, and also because he is ignorant of what is before him, and always
at a loss. 

Theod. That is very true, Socrates. 

Soc. But, O my friend, when he draws the other into upper air, and
gets him out of his pleas and rejoinders into the contemplation of
justice and injustice in their own nature and in their difference
from one another and from all other things; or from the commonplaces
about the happiness of a king or of a rich man to the consideration
of government, and of human happiness and misery in general-what they
are, and how a man is to attain the one and avoid the other-when that
narrow, keen, little legal mind is called to account about all this,
he gives the philosopher his revenge; for dizzied by the height at
which he is hanging, whence he looks down into space, which is a strange
experience to him, he being dismayed, and lost, and stammering broken
words, is laughed at, not by Thracian handmaidens or any other uneducated
persons, for they have no eye for the situation, but by every man
who has not been brought up a slave. Such are the two characters,
Theodorus: the one of the freeman, who has becomes trained in liberty
and leisure, whom you call the philosopher-him we cannot blame because
he appears simple and of no account when he has to perform some menial
task, such as packing up bed-clothes, or flavouring a sauce or fawning
speech; the other character is that of the man who is able to do all
this kind of service smartly and neatly, but knows not how to wear
his cloak like a gentleman; still less with the music of discourse
can he hymn the true life aright which is lived by immortals or men
blessed of heaven. 

Theod. If you could only persuade everybody, Socrates, as you do me,
of the truth of your words, there would be more peace and fewer evils
among men. 

Soc. Evils, Theodorus, can never pass away; for there must always
remain something which is antagonistic to good. Having no place among
the gods in heaven, of necessity they hover around the mortal nature,
and this earthly sphere. Wherefore we ought to fly away from earth
to heaven as quickly as we can; and to fly away is to become like
God, as far as this is possible; and to become like him, is to become
holy, just, and wise. But, O my friend, you cannot easily convince
mankind that they should pursue virtue or avoid vice, not merely in
order that a man may seem to be good, which is the reason given by
the world, and in my judgment is only a repetition of an old wives
fable. Whereas, the truth is that God is never in any way unrighteous-he
is perfect righteousness; and he of us who is the most righteous is
most like him. Herein is seen the true cleverness of a man, and also
his nothingness and want of manhood. For to know this is true wisdom
and virtue, and ignorance of this is manifest folly and vice. All
other kinds of wisdom or cleverness, which seem only, such as the
wisdom of politicians, or the wisdom of the arts, are coarse and vulgar.
The unrighteous man, or the sayer and doer of unholy things, had far
better not be encouraged in the illusion that his roguery is clever;
for men glory in their shame -they fancy that they hear others saying
of them, "These are not mere good-for nothing persons, mere burdens
of the earth, but such as men should be who mean to dwell safely in
a state." Let us tell them that they are all the more truly what they
do not think they are because they do not know it; for they do not
know the penalty of injustice, which above all things they ought to
know-not stripes and death, as they suppose, which evil-doers often
escape, but a penalty which cannot be escaped. 

Theod. What is that? 

Soc. There are two patterns eternally set before them; the one blessed
and divine, the other godless and wretched: but they do not see them,
or perceive that in their utter folly and infatuation they are growing
like the one and unlike the other, by reason of their evil deeds;
and the penalty is, that they lead a life answering to the pattern
which they are growing like. And if we tell them, that unless they
depart from their cunning, the place of innocence will not receive
them after death; and that here on earth, they will live ever in the
likeness of their own evil selves, and with evil friends-when they
hear this they in their superior cunning will seem to be listening
to the talk of idiots. 

Theod. Very true, Socrates. 

Soc. Too true, my friend, as I well know; there is, however, one peculiarity
in their case: when they begin to reason in private about their dislike
of philosophy, if they have the courage to hear the argument out and
do not run away, they grow at last strangely discontented with themselves;
their rhetoric fades away, and they become helpless as children. These
however are digressions from which we must now desist, or they will
overflow, and drown the original argument; to which, if you please,
we will now return. 

Theod. For my part, Socrates, I would rather have the digressions,
for at my age I find them easier to follow; but if you wish, let us
go back to the argument. 

Soc. Had we not reached the point at which the partisans of the perpetual
flux, who say that things are as they seem to each one, were confidently
maintaining that the ordinances which the state commanded 2nd thought
just, were just to the state which imposed them, while they were in
force; this was especially asserted of justice; but as to the good,
no one had any longer the hardihood to contend of any ordinances which
the state thought and enacted to be good that these, while they were
in force, were really good;-he who said so would be playing with the
name "good," and would, not touch the real question-it would be a
mockery, would it not? 

Theod. Certainly it would. 

Soc. He ought not to speak of the name, but of the thing which is
contemplated under the name. 

Theod. Right. 

Soc. Whatever be the term used, the good or expedient is the aim of
legislation, and as far as she has an opinion, the state imposes all
laws with a view to the greatest expediency; can legislation have
any other aim? 

Theod. Certainly not. 

Soc. But is the aim attained always? do not mistakes often happen?

Theod. Yes, I think that there are mistakes. 

Soc. The possibility of error will be more distinctly recognized,
if we put the question in reference to the whole class under which
the good or expedient fall That whole class has to do with the future,
and laws are passed under the idea that they will be useful in after-time;
which, in other words, is the future. 

Theod. Very true. 

Soc. Suppose now, that we ask Protagoras, or one of his disciples,
a question:-O, Protagoras, we will say to him, Man is, as you declare,
the measure of all things-white, heavy, light: of all such things
he is the judge; for he has the criterion of them in himself, and
when he thinks that things are such as he experiences them to be,
he thinks what is and is true to himself. Is it not so? 

Theod. Yes. 

Soc. And do you extend your doctrine, Protagoras (as we shall further
say), to the future as well as to the present; and has he the criterion
not only of what in his opinion is but of what will be, and do things
always happen to him as he expected? For example, take the case of
heat:-When an ordinary man thinks that he is going to have a fever,
and that this kind of heat is coming on, and another person, who is
a physician, thinks the contrary, whose opinion is likely to prove
right? Or are they both right?-he will have a heat and fever in his
own judgment, and not have a fever in the physician's judgment?

Theod. How ludicrous! 

Soc. And the vinegrower, if I am not mistaken, is a better judge of
the sweetness or dryness of the vintage which is not yet gathered
than the harp-player? 

Theod. Certainly. 

Soc. And in musical composition-the musician will know better than
the training master what the training master himself will hereafter
think harmonious or the reverse? 

Theod. Of course. 

Soc. And the cook will be a better judge than the guest, who is not
a cook, of the pleasure to be derived from the dinner which is in
preparation; for of present or past pleasure we are not as yet arguing;
but can we say that every one will be to himself the best judge of
the pleasure which will seem to be and will be to him in the future?-nay,
would not you, Protagoras, better guess which arguments in a court
would convince any one of us than the ordinary man? 

Theod. Certainly, Socrates, he used to profess in the strongest manner
that he was the superior of all men in this respect. 

Soc. To be sure, friend: who would have paid a large sum for the privilege
of talking to him, if he had really persuaded his visitors that neither
a prophet nor any other man was better able to judge what will be
and seem to be in the future than every one could for himself?

Theod. Who indeed? 

Soc. And legislation and expediency are all concerned with the future;
and every one will admit that states, in passing laws, must often
fail of their highest interests? 

Theod. Quite true. 

Soc. Then we may fairly argue against your master, that he must admit
one man to be wiser than another, and that the wiser is a measure:
but I, who know nothing, am not at all obliged to accept the honour
which the advocate of Protagoras was just now forcing upon me, whether
I would or not, of being a measure of anything. 

Theod. That is the best refutation of him, Socrates; although he is
also caught when he ascribes truth to the opinions of others, who
give the lie direct to his own opinion. 

Soc. There are many ways, Theodorus, in which the doctrine that every
opinion of: every man is true may be refuted; but there is more difficulty,
in proving that states of feeling, which are present to a man, and
out of which arise sensations and opinions in accordance with them,
are also untrue. And very likely I have been talking nonsense about
them; for they may be unassailable, and those who say that there is
clear evidence of them, and that they are matters of knowledge, may
probably be right; in which case our friend Theaetetus was not so
far from the mark when he identified perception and knowledge. And
therefore let us draw nearer, as the advocate of Protagoras desires;
and the truth of the universal flux a ring: is the theory sound or
not? at any rate, no small war is raging about it, and there are combination
not a few. 

Theod. No small, war, indeed, for in most the sect makes rapid strides,
the disciples of Heracleitus are most energetic. upholders of the

Soc. Then we are the more bound, my dear Theodorus, to examine the
question from the foundation as it is set forth by themselves.

Theod. Certainly we are. About these speculations of Heracleitus,
which, as you say, are as old as Homer, or even older still, the Ephesians
themselves, who profess to know them, are downright mad, and you cannot
talk with them on the subject. For, in accordance with their text-books,
they are always in motion; but as for dwelling upon an argument or
a question, and quietly asking and answering in turn, they can no
more do so than they can fly; or rather, the determination of these
fellows not to have a particle of rest in them is more than the utmost
powers of negation can express. If you ask any of them a question,
he will produce, as from a quiver, sayings brief and dark, and shoot
them at you; and if you inquire the reason of what he has said, you
will be hit by some other newfangled word, and will make no way with
any of them, nor they with one another; their great care is, not to
allow of any settled principle either in their arguments or in their
minds, conceiving, as I imagine, that any such principle would be
stationary; for they are at war with the stationary, and do what they
can to drive it out everywhere. 

Soc. I suppose, Theodorus, that you have only seen them when they
were fighting, and have never stayed with them in time of peace, for
they are no friends of yours; and their peace doctrines are only communicated
by them at leisure, as I imagine, to those disciples of theirs whom
they want to make like themselves. 

Theod. Disciples! my good sir, they have none; men of their sort are
not one another's disciples, but they grow up at their own sweet will,
and get their inspiration anywhere, each of them saying of his neighbour
that he knows nothing. Fro these men, then, as I was going to remark,
you will never get a reason, whether with their will or without their
will; we must take the question out of their hands, and make the analysis
ourselves, as if we were doing geometrical problem. 

Soc. Quite right too; but as touching the aforesaid problem, have
we not heard from the ancients, who concealed their wisdom from the
many in poetical figures, that Oceanus and Tethys, the origin of all
things, are streams, and that nothing is at rest? And now the moderns,
in their superior wisdom, have declared the same openly, that the
cobbler too may hear and learn of them, and no longer foolishly imagine
that some things are at rest and others in motion-having learned that
all is motion, he will duly honour his teachers. I had almost forgotten
the opposite doctrine, Theodorus, 

Alone Being remains unmoved, which is the name for the all. This is
the language of Parmenides, Melissus, and their followers, who stoutly
maintain that all being is one and self-contained, and has no place
which to move. What shall we do, friend, with all these people; for,
advancing step by step, we have imperceptibly got between the combatants,
and, unless we can protect our retreat, we shall pay the penalty of
our rashness-like the players in the palaestra who are caught upon
the line, and are dragged different ways by the two parties. Therefore
I think that we had better begin by considering those whom we first
accosted, "the river-gods," and, if we find any truth in them, we
will help them to pull us over, and try to get away from the others.
But if the partisans of "the whole" appear to speak more truly, we
will fly off from the party which would move the immovable, to them.
And if I find that neither of them have anything reasonable to say,
we shall be in a ridiculous position, having so great a conceit of
our own poor opinion and rejecting that of ancient and famous men.
O Theodorus, do you think that there is any use in proceeding when
the danger is so great? 

Theod. Nay, Socrates, not to examine thoroughly what the two parties
have to say would be quite intolerable. 

Soc. Then examine we must, since you, who were so reluctant. to begin,
are so eager to proceed. The nature of motion appears to be the question
with which we begin. What do they mean when they say that all things
are in motion? Is there only one kind of motion, or, as I rather incline
to think, two? should like to have your opinion upon this point in
addition to my own, that I may err, if I must err, in your company;
tell me, then, when a thing changes from one place to another, or
goes round in the same place, is not that what is called motion?

Theod. Yes. 

Soc. Here then we have one kind of motion. But when a thing, remaining
on the same spot, grows old, or becomes black from being white, or
hard from being soft, or undergoes any other change, may not this
be properly called motion of another kind? 

Theod. I think so. 

Soc. Say rather that it must be so. Of motion then there are these
two kinds, "change," and "motion in place." 

Theod. You are right. 

Soc. And now, having made this distinction, let us address ourselves
to those who say that all is motion, and ask them whether all things
according to them have the two kinds of motion, and are changed as
well as move in place, or is one thing moved in both ways, and another
in one only? 

Theod. Indeed, I do not know what to answer; but I think they would
say that all things are moved in both ways. 

Soc. Yes, comrade; for, if not, they would have to say that the same
things are in motion and at rest, and there would be no more truth
in saying that all things are in motion, than that all things are
at rest. 

Theod. To be sure. 

Soc. And if they are to be in motion, and nothing is to be devoid
of motion, all things must always have every sort of motion?

Theod. Most true. 

Soc. Consider a further point: did we not understand them to explain
the generation of heat, whiteness, or anything else, in some such
manner as the following:-were they not saying that each of them is
moving between the agent and the patient, together with a perception,
and that the patient ceases to be a perceiving power and becomes a
percipient, and the agent a quale instead of a quality? I suspect
that quality may appear a strange and uncouth term to you, and that
you do not understand the abstract expression. Then I will take concrete
instances: I mean to say that the producing power or agent becomes
neither heat nor whiteness but hot and white, and the like of other
things. For I must repeat what I said before, that neither the agent
nor patient have any absolute existence, but when they come together
and generate sensations and their objects, the one becomes a thing
a certain quality, and the other a percipient. You remember?

Theod. Of course. 

Soc. We may leave the details of their theory unexamined, but we must
not forget to ask them the only question with which we are concerned:
Are all things in motion and flux? 

Theod. Yes, they will reply. 

Soc. And they are moved in both those ways which we distinguished,
that is to Way, they move in place and are also changed?

Theod. Of course, if the motion is to be perfect. 

Soc. If they only moved in place and were not changed, we should be
able to say what is the nature of the things which are in motion and

Theod. Exactly. 

Soc. But now, since not even white continues to flow white, and whiteness
itself is a flux or change which is passing into another colour, and
is never to be caught standing still, can the name of any colour be
rightly used at all? 

Theod. How is that possible, Socrates, either in the case of this
or of any other quality-if while we are using the word the object
is escaping in the flux? 

Soc. And what would you say of perceptions, such as sight and hearing,
or any other kind of perception? Is there any stopping in the act
of seeing and hearing? 

Theod. Certainly not, if all things are in motion. 

Soc. Then we must not speak of seeing any more than of not-seeing,
nor of any other perception more than of any non-perception, if all
things partake of every kind of motion? 

Theod. Certainly not. 

Soc. Yet perception is knowledge: so at least Theaetetus and I were

Theod. Very true. 

Soc. Then when we were asked what is knowledge, we no more answered
what is knowledge than what is not knowledge? 

Theod. I suppose not. 

Soc. Here, then, is a fine result: we corrected our first answer in
our eagerness to prove that nothing is at rest. But if nothing is
at rest, every answer upon whatever subject is equally right: you
may say that a thing is or is not thus; or, if you prefer, "becomes"
thus; and if we say "becomes," we shall not then hamper them with
words expressive of rest. 

Theod. Quite true. 

Soc. Yes, Theodorus, except in saying "thus" and "not thus." But you
ought not to use the word "thus," for there is no motion in "thus"
or in "not thus." The maintainers of the doctrine have as yet no words
in which to express themselves, and must get a new language. I know
of no word that will suit them, except perhaps "no how," which is
perfectly indefinite. 

Theod. Yes, that is a manner of speaking in which they will be quite
at home. 

Soc. And so, Theodorus, we have got rid of your friend without assenting
to his doctrine, that every man is the measure of all things-a wise
man only is a measure; neither can we allow that knowledge is perception,
certainly not on the hypothesis of a perpetual flux, unless perchance
our friend Theaetetus is able to convince us that it is.

Theod. Very good, Socrates; and now that the argument about the doctrine
of Protagoras has been completed, I am absolved from answering; for
this was the agreement. 

Theaet. Not, Theodorus, until you and Socrates have discussed the
doctrine of those who say that all things are at rest, as you were

Theod. You, Theaetetus, who are a young rogue, must not instigate
your elders to a breach of faith, but should prepare to answer Socrates
in the remainder of the argument. 

Theaet. Yes, if he wishes; but I would rather have heard about the
doctrine of rest. 

Theod. Invite Socrates to an argument-invite horsemen to the open
plain; do but ask him, and he will answer. 

Soc. Nevertheless, Theodorus, I am afraid that I shall not