Theaetetus - Platonic Foundation

Theaetetus

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persons in the dialogue: EUCLIDES founder of Megarian school

TERPSION of Megara, friend of Euclides

MALE SLAVE of Euclides, oral reader

THEODORUS of Cyrene, geometer

THEAETETUS of Sounion, mathematician, geometer

SOCRATES of Alopece, son of Sophroniscus

also present: YOUNG SOCRATES a young Athenian

PROTAGORAS of Abdera, renowned sophist

OTHER YOUTHS

scenes: at the house of Euclides in Megara

in a gymnasium in Athens

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EUCLIDES: Ah, Terpsion, have you arrived from the country just now, or was it some time ago?

TERPSION: Quite some time ago. Indeed, I was looking for you around the marketplace and was

surprised that I could not find you.

EUCLIDES: Actually, I wasn’t in the city.

TERPSION: Where were you then?

EUCLIDES: As I was going down to the harbour, I came across Theaetetus being carried back to

Athens from the army camp at Corinth.

TERPSION: Was he alive or dead?

EUCLIDES: Alive, but just barely so. He is in a bad way on account of his wounds, but worse still,

he has caught the disease that broke out in the army.

TERPSION: Oh, the dysentery?

EUCLIDES: Yes.

TERPSION: What a man he is! And you say he is in peril of his life?

EUCLIDES: A noble and good man, Terpsion. In fact, I also heard some people just now, full of

praise for his role in the battle.

TERPSION: That is nothing particularly unusual. Indeed, it would have been much more surprising

if he hadn’t played such a role. More to the point, why did the man not stay here in

Megara?

EUCLIDES: He was in a hurry to get home. Indeed, I asked him myself and advised him to stay, but

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THEAETETUS – 142a–142c | 155

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The dialogue’s first two speakers, Euclides and Terpsion of Megara, were both followers of Socrates. Euclides is cred-

ited with having founded the Megarian school of philosophy.

Theaetetus was mortally wounded in the war between Athens and Sparta.

Theaetetus, David Horan translation, 6 Nov 25

he did not want to. So, I saw him on his way, and as I was coming back I was reminded of

Socrates, and how prophetically he spoke in general, and about Theaetetus in particular.

Socrates met him as a young man, I believe, shortly before his own death, and from the

company and the discussions he was very pleased with his character. He recounted their

discussions to me when I arrived in Athens, and they are well worth hearing, and he said

that Theaetetus really must become famous, if he actually lived long enough.

TERPSION: Well, it seems he was right about that anyway. But what were these discussions? Can

you recount them?

EUCLIDES: No, by Zeus, not from memory at any rate. But I made notes at the time as soon as I

arrived home, and later on I recollected them at my leisure and wrote them out. And when-

ever I went to Athens, I would ask Socrates again about whatever I did not remember, and

once I got back here I would make corrections, so that I have now written out almost the

entire discussion.

TERPSION: Yes, I have heard you say that before, and in fact I had always intended to ask you to

present it, but I have put it off until now. But why don’t we go through it now? Having just

come in from the country, I really need to rest.

EUCLIDES: Actually, rest is not an unpleasant prospect for me either, as I accompanied Theaetetus

as far as Erineos. So let’s go inside, and this servant can read to us while we rest.

TERPSION: Well said.

EUCLIDES: Now, this is the book, Terpsion. See the way I wrote the account not as Socrates

recounted it to me, but as a dialogue with the men he was talking to, and he said these were

the geometers Theodorus and Theaetetus. I wished to avoid inserting phrases between the

words that were spoken, such as ‘and I declared’ or ‘said’, whenever Socrates spoke, or

again ‘he concurred’ or ‘he disagreed’, whenever the respondent spoke. For this reason I

wrote it as direct discourse, omitting all such phrases.

TERPSION: There is no problem with that, Euclides.

EUCLIDES: Well then, take the book and read it, boy.

SOCRATES: Theodorus, if I cared more about people in Cyrene,

I would ask you about its affairs

and its populace, and whether any of the young folk there are showing any interest in geom-

etry or any other branch of wisdom. But, in fact, my love for them is less than for the

Athenians, so I am more eager to know which of our young people are likely to turn out

well. I watch out for such young men myself as best I can, and I also ask others, once I see

that the young want to associate with them. Of course, they come to you in no small num-

bers, and rightly so, as you deserve it in general, and also because of your knowledge of

geometry. So, if you have come across anyone worthy of report, I would be glad to hear

about them.

THEODORUS: Well, Socrates, I have come across one such young man among your citizenry, and

it is well worth hearing what I have to say about him. Now, if he were handsome, I would

be afraid to speak enthusiastically lest I might seem to have feelings for him. Now, and I

hope I don’t upset you when I say, he is not handsome and he is quite like you, with the

snub nose and bulging eyes, though they are less pronounced in his case. So I am speaking

without fear.

You may rest assured that of all the youths I met previously – and there have been

many – I have seen none with such wonderful natural endowments. I never imagined that

a man who learns so keenly what others find difficult could still be extremely modest and

also as manly as anyone else, and I do not see this happening elsewhere. But those who are

sharp-witted and intelligent and have good memories, like this fellow, are often quick to

anger and are borne hither and thither like ships without ballast, being more mad than manly,

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156 | THEAETETUS – 142d–144a

while the slower sort approach study with some reluctance and are full of forgetfulness.

But this youth takes to learning and enquiry so smoothly, steadily and productively, with

great modesty, like a stream of silently flowing oil, that you are amazed that one so young

could achieve so much.

SOCRATES: That is good news. But which of our citizens is his father?

THEODORUS: I have heard his name, but do not remember it. But look, he is the one in the middle

of the group coming towards us. The young man and these companions of his were oiling

themselves a moment ago on the running track outside, and they seem to have finished that

now, so they are coming in here. See if you recognise him.

SOCRATES: I do recognise him. It is the son of Euphronios of Sounion,

a man who was very like

the boy you described and generally well regarded; and, indeed, he also left quite a sub-

stantial inheritance. But I do not know the young man’s name.

THEODORUS: Socrates, his name is Theaetetus. However, I believe that the inheritance has been

squandered by the trustees. But, nevertheless, he is wonderfully generous with his money,

Socrates.

SOCRATES: You are describing an excellent man. Ask him to come here and sit beside me.

THEODORUS: I shall. Theaetetus, sit here beside Socrates.

SOCRATES: Yes, indeed, Theaetetus, so that I can scrutinise for myself the sort of face I have, for

Theodorus says that I have a face like yours. However, if we both had lyres, and he said

that they were tuned in like manner, would we just believe him or would we find out whether

he was speaking as a musician?

THEAETETUS: We would find that out.

SOCRATES: We would believe him, would we not, if we discovered he was a musician, but we

would be unconvinced if he were not?

THEAETETUS: True.

SOCRATES: Now, I presume that if the similarity of our faces is of any concern to us, we would ask

if the speaker was a portrait artist or not.

THEAETETUS: I think so.

SOCRATES: And does Theodorus know portraiture?

THEAETETUS: Not as far as I know anyway.

SOCRATES: Nor geometry either?

THEAETETUS: He certainly does know geometry, Socrates.

SOCRATES: What about astronomy, calculation, music and the various branches of education?

THEAETETUS: Well, I think so.

SOCRATES: Well then, if he says that there is some physical resemblance between us, which he

either praises or criticises, it is not worth paying much attention to him.

THEAETETUS: Perhaps not.

SOCRATES: However, what if he were to praise either of our souls for wisdom or excellence?

Wouldn’t it be good for the recipient of the praise to exhibit his quality eagerly, while the

other watches him closely?

THEAETETUS: Yes certainly, Socrates.

SOCRATES: Now, the time has come, dear Theaetetus, for you to give your demonstration whilst I

watch closely, since, mark my words, Theodorus has praised many strangers and citizens

to me, but never in the way that he praised you just now.

THEAETETUS: That’s all very well, Socrates, but take care that he was not speaking in jest.

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THEAETETUS – 144b–145c | 157

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Cyrene, Theodorus’ home town, was a Greek city in north Africa.

The Cape of Sounion marks the southernmost part of Attica, the territory belonging to Athens.

Theaetetus, David Horan translation, 6 Nov 25

SOCRATES: No, that is not Theodorus’ way. But do not be hesitant about our agreement by pretend-

ing that this man is jesting, in case we have to call him as a witness. No one will doubt his

words, so just stand bravely by our agreement.

THEAETETUS: Well, if it seems right to you, that is what I must do.

SOCRATES: Now, tell me this. I presume you are learning some geometry from Theodorus?

THEAETETUS: I am indeed.

SOCRATES: And astronomy, harmony and calculation?

THEAETETUS: Well, I am trying to, anyway.

SOCRATES: Yes. And so am I, my boy, from Theodorus and others who, I believe, have some

knowledge of these topics. And although I fare quite well with them in most respects, I am

perplexed over a minor issue that I must consider with you, and our friends here. Now, tell

me. Does learning not consist in becoming wiser about whatever one is learning?

THEAETETUS: How could it be otherwise?

SOCRATES: And it is on account of wisdom, I imagine, that the wise are wise.

THEAETETUS: Yes.

SOCRATES: And does this differ in any way from knowledge?

THEAETETUS: Does what differ?

SOCRATES: Wisdom! Aren’t people wise in the matters in which they are knowledgeable?

THEAETETUS: Of course.

SOCRATES: So are knowledge and wisdom the same?

THEAETETUS: Yes.

SOCRATES: Well now, this is what perplexes me, and I cannot grasp adequately for myself what

knowledge actually is. So now can we speak of this? What do you say? Which of us will

speak first? If he goes wrong he will sit down, and whoever goes wrong after him will

also sit down and be ‘donkey’, as the children say in the ball game. But whoever comes

through without error will be our king, and may order us to answer any question he likes.

Why are you silent? Hopefully I am not being ill-mannered, Theodorus, due to my love of

discourse, and eagerness to make us engage in discourse, and become friendly and familiar

with one another.

THEODORUS: Oh there is nothing ill-mannered about that, Socrates. But direct one of the young

men to respond to you, since I am unaccustomed to such discussions as these, and I am too

old to get used to them now. It would be suitable for these chaps, and they would make

much more progress, since in truth the young make more progress in everything. So go on,

just as you began. Don’t give up on Theaetetus. Question him.

SOCRATES: Now, Theaetetus, you hear what Theodorus is saying, and I doubt if you would wish to

disbelieve him, nor is it proper for a younger man to disobey the directions of a wise man

in such matters. Come on, declare clearly and nobly what you think knowledge is.

THEAETETUS: Well, Socrates, I must, since you are both telling me to do so. In any event, if I make

any error you will correct it.

SOCRATES: Yes, certainly, if we are able to.

THEAETETUS: I think that whatever one learns from Theodorus is knowledge – geometry and those

subjects you listed just now – and so also is cobbling and the other manufacturing skills.

Each of these and all of these are knowledge, and not something else.

SOCRATES: How noble and generous, my friend. You are asked for one thing and you provide many,

favouring variety over simplicity.

THEAETETUS: Why do you say that, Socrates?

SOCRATES: Well, perhaps it is nothing, but I shall tell you what I think anyway. Whenever you refer

to cobbling, are you talking about anything other than the knowledge of making shoes?

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158 | THEAETETUS – 145d–146d

THEAETETUS: Nothing else.

SOCRATES: And what about carpentry? Do you mean anything other than the knowledge of making

wooden objects?

THEAETETUS: No, that’s it.

SOCRATES: In both cases, aren’t you defining what each is knowledge of?

THEAETETUS: Yes.

SOCRATES: But, Theaetetus, you were not asked what knowledge is of, or how many kinds there

are. That was not the point. Indeed, we did not ask the question from a desire to count them,

but we wanted to know what knowledge itself actually is. Or am I making no sense?

THEAETETUS: No, you are absolutely correct.

SOCRATES: Well, consider this also. If someone were to ask us about one of the ordinary things

around us – for example, what clay is – would we not be silly to answer potters’ clay, oven-

makers’ clay, brick-makers’ clay?

THEAETETUS: Surely.

SOCRATES: Firstly, we would be silly to imagine that the questioner understands anything from

our answers whenever we say ‘clay’, whether we add ‘of modellers’ or of any other crafts-

men. Or do you think anyone understands any name of anything without knowing what

that thing is?

THEAETETUS: Not at all.

SOCRATES: Then neither does anyone understand knowledge of shoe-making who does not know

knowledge.

THEAETETUS: He does not.

SOCRATES: So, whoever is ignorant of knowledge does not understand cobbling or any other skill.

THEAETETUS: That’s it.

SOCRATES: So, when we respond with the name of some skill when we are asked what knowledge

is, that is a ridiculous answer. Indeed the answer says ‘knowledge of something’, and that

does not answer the question.

THEAETETUS: So it seems.

SOCRATES: Well then, we seem to be going the long way around instead of answering plainly and

briefly. Thus, on the question about clay, we could say, plainly and simply, that it is earth

mixed with water, regardless of whose clay it is.

THEAETETUS: Oh it seems easy when you put it like that, Socrates. However, it is very likely that

what you are asking about is like what came up recently in conversation between myself

and your namesake here, Socrates.

SOCRATES: Like what, Theaetetus?

THEAETETUS: Theodorus here was illustrating something about powers to us, showing that a three-

foot square and a five-foot square do not have a common measure with respect to a single

foot. He dealt with each in this way until he reached seventeen, and then he stopped for

some reason. Now, since the number of powers appeared unlimited, it occurred to us to try

to comprehend them into a unity by which we could refer to all these powers.

SOCRATES: And did you find something like this?

THEAETETUS: I think that we did. But see if you agree.

SOCRATES: Tell me.

THEAETETUS: We divided all number into two. Those that arise by multiplying equal numbers we

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THEAETETUS – 146e–147e | 159

–––––

Socrates the Younger was a companion of Theaetetus, later a member of Plato’s Academy. He is also mentioned in the

two dramatic successor dialogues to the Theaetetus – the Sophist, in which he is mentioned briefly, and the Statesman,

in which, together with the Eleatic Stranger, he is one of the main interlocutors.

Theaetetus, David Horan translation, 6 Nov 25

likened to a square shape, and called them both square and equilateral numbers.

SOCRATES: Yes, that’s good.

THEAETETUS: However, between these numbers are all those, such as three and five, which cannot

be generated by multiplying equal numbers. These are produced by multiplying greater by

lesser, or lesser by greater, and the sides that enclose them are of different lengths, so we

likened them to an oblong shape, and called them oblong numbers.

SOCRATES: Excellent. But what did you do next?

THEAETETUS: Whatever lines form an equilateral flat number

when they are made into squares,

we defined as magnitudes, while the lines whose squares form an oblong flat number, we

defined as powers, as they do not have a measure, common in magnitude, with the other

magnitudes, though the flat numbers they can form do have such a measure. Similar con-

siderations apply to solid structures.

SOCRATES: Well that is excellent, my boys, and I don’t think that Theodorus will be open to a charge

of perjury.

THEAETETUS: Very well, Socrates, but I would not be able to answer what you are asking about

knowledge in the very way I spoke about magnitudes and powers. However, I think that’s

the sort of wording you are looking for, so Theodorus may prove false after all.

SOCRATES: Well, suppose he had praised you as a runner, saying that he had never come across a

young man who could run like this, and you were then beaten in a race by the champion in

his prime. Do you think that his praise would be any less true?

THEAETETUS: I do not.

SOCRATES: And do you think that the search for knowledge, in the manner I have just described, is

something trivial, or a task for those at the pinnacle in every respect?

THEAETETUS: Oh, by Zeus, I really believe it is for those at the absolute pinnacle.

SOCRATES: Well then, be confident about yourself. Believe that Theodorus is right, and exert

yourself in every way, both in general and to arrive at an account of what knowledge

actually is.

THEAETETUS: If exertion is all we need, Socrates, it will come to light.

SOCRATES: Go on then. Indeed, you showed the approach very nicely just now, so try imitating

your answer about powers. Just as you encompassed the many powers in a single form, so

also describe the many types of knowledge in a single account.

THEAETETUS: Be assured, Socrates, that I have embarked upon this enquiry many times on hearing

reports of the questions you ask. However, I am never able to persuade myself that I have

anything useful to say, nor have I heard anyone else speaking in the way you are exhorting

me. Then again, I can’t give up the preoccupation either.

SOCRATES: For you are in labour, dear Theaetetus, because you have conceived and are not barren.

THEAETETUS: I don’t know about that, Socrates. I am only describing what I experience.

SOCRATES: How comical! Have you not heard that I am the son of a fine, burly midwife named

Phaenarete?

THEAETETUS: Yes, I heard that before.

SOCRATES: Now, have you also heard that I practise the same skill?

THEAETETUS: Not at all.

SOCRATES: Well it is true, believe me! But you must not tell everyone else about me, my friend, as

they are unaware that I have this skill. And since they do not know this about me, they never

say it. But they do say that I am very strange, and that I make men perplexed. Surely you

have also heard that?

THEAETETUS: I have, indeed.

SOCRATES: Well, shall I tell you the reason?

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160 | THEAETETUS – 148a–149b

THEAETETUS: Yes, certainly.

SOCRATES: Well, if you consider the status of all midwives overall, you will understand what I

mean more easily. Indeed, I presume you know that no women, who are themselves still

conceiving and bearing children, act as midwives to others, but only those who can no

longer bear children.

THEAETETUS: Yes, certainly.

SOCRATES: Artemis is responsible for this, so they say, because she has been allotted responsibility

for child-bearing, though she is childless.

So she did not give the midwife’s role to those

who are barren, since human nature is too weak to understand a skill of which it has no

experience. Instead, she assigned it to those who are past child-bearing age, in honour of

their likeness to herself.

THEAETETUS: Quite likely.

SOCRATES: And isn’t it both likely, and necessarily the case, that the midwives recognise, better

than anyone, which women are with child and which are not?

THEAETETUS: Yes, indeed.

SOCRATES: And, indeed, the midwives are able to arouse the pangs or allay them as they so wish

by administering potions or incantations. They can deliver difficult births, and if they believe

the embryo should miscarry, they bring on miscarriage.

THEAETETUS: This is so.

SOCRATES: Well, have you noticed something else about them? That they are the most ingenious

matchmakers since they are omniscient when it comes to knowing the types of men with

whom various women should consort to produce the most excellent children?

THEAETETUS: No, I didn’t know that at all.

SOCRATES: Then rest assured that they value this skill more than the cutting of the umbilical cord.

Yes, think about it. Do you believe that tending and harvesting the fruits of the earth is the

same skill as knowing the types of plants that should be sown in various types of soil?

THEAETETUS: It is the same skill.

SOCRATES: And with a woman, my friend, do you think there is one skill dealing with types and

another dealing with offspring?

THEAETETUS: That is not very likely.

SOCRATES: No, it is not. However, because men and women are brought together in an improper

and unskilled manner, which is called procuring, the midwives shun matchmaking, as they

are respectable women who fear that through involvement in matchmaking they may be

accused of procuring. Yet proper matchmaking is somehow a role only for the true mid-

wives.

THEAETETUS: So it appears.

SOCRATES: Such is the role of the midwives, but it is a lesser role than mine. Indeed, it is not the

custom of women to bring forth images on some occasions, and at other times true offspring,

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THEAETETUS – 149c–150b | 161

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A flat number is a square whose area is equal to the number, and so the side of the square, here called the line, is equal

to the square root of the number. So, in the examples given, 3 as a flat number has a common measure with 4, but the

side of the flat number 3 is √3, while the side of the flat number 4 is 2, and they have no common measure since √3

cannot be expressed as a fraction so as to yield a simple numerical ratio of 2. The term irrational is used to describe

√3, but the entire process here is being described geometrically rather than arithmetically, and the lack of a common

measure, called incommensurability, captures the essence of the problem. Contrast 4 and 9 where the sides (of the

square) or magnitudes are 2 and 3, and so they have a common measure, and relate as 2/3, as also do 16 and 36: √16

= 4, √36 = 6, 4:6 −> 2:3. However, this process will not work with, for example, 15 and 36.

Socrates’ mother’s name means ‘she who brings excellence to light’.

Artemis, goddess of the hunt and sister of Apollo, was the protectress of young animals and of women, particularly at

the time of childbirth.

Theaetetus, David Horan translation, 6 Nov 25

which are not easy to distinguish. If women did this, the greatest and noblest task of mid-

wives would be to decide which was true and which was not. Do you not agree?

THEAETETUS: I do, indeed.

SOCRATES: Now, my skill of midwifery is, in general, similar in character to theirs, but it differs by

delivering men and not women, and by looking after their souls rather than their bodies

when in labour. But the greatest thing about my skill is that it is able to test, in every respect,

whether the mind of the young man is bringing forth an image and a lie, or something gen-

uine and true.

Now, I do have this in common with the female midwives: I bring to birth no wis-

dom. And many people reproach me for this, since I ask questions of others while I myself

proclaim nothing about anything, because I have no wisdom. Their reproach is true, but the

reason is that the god compels me to act as a midwife and has prevented me from giving

birth. So, of course, I myself am not at all wise, nor have I any invention that is born of my

own soul. However, it is different for those who associate with me. Some of them also

appear quite ignorant at first, but as our relationship proceeds, all whom the god allows,

progress to a wonderful degree. Such is their own belief and that of others, and it is obvious

that they have never learned anything from me. Rather, they have discovered from them-

selves much that is beautiful, and have brought it to birth. However, both I and the god are

responsible for the delivery. The proof is that over the years, many who were ignorant of

this regarded themselves as responsible, despised me, and went away sooner than they

should, persuaded either by themselves or by others. But once they had left me, they mis-

carried whatever remained within them through bad company, and destroyed through

improper care whatever fruits I had delivered from them. Placing more value on images

and lies than upon the truth, they ended up being regarded as ignorant both by themselves

and by everyone else.

One such person was Aristides, the son of Lysimachus,

and there have been many

others. If these men ever come back again, imploring my company with extraordinary

imprecations, the familiar daimon

forbids me from associating with some of them, while

it allows me to associate with others, and these men make progress once more.

Now, my associates have another experience in common with women in childbirth.

They are pained and full of distress both night and day, even more than the women, but my

skills can arouse or relieve this pain, and that is the plight they are in. But, Theaetetus, some

who seem to me to have nothing within them to bring forth, I matchmake favourably with

someone else, and with God’s help I guess quite competently whose company will benefit

them, knowing that they have no need for me. I have handed many over to Prodicus,

and

many to other wise and inspired men.

Now, excellent friend, the reason I am speaking to you at such length is that I suspect,

as you yourself believe, that you are pained by something you are carrying within. So come

to me, the son of a midwife, who is skilled in the midwife’s art, and strive to answer my

questions as best you can. And if I consider something you have been saying to be an image

and untrue, and I take it out and discard it, do not be angry with me like new mothers over

their children. Indeed, many before you, dear friend, had such an attitude towards me as to

actually bite me whenever I take something nonsensical away from them. They do not

believe that I do this with good intentions, and they are far from realising that no god ever

intends harm towards humanity, nor do I act in this way from ill intentions. But I am not

allowed to accept falsehood or to conceal the truth. So start again, Theaetetus, and try to

state what knowledge actually is. And do not say that you are not able, for if God wills it

and you summon up your manhood, you will be able.

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162 | THEAETETUS – 150c–151d

THEAETETUS: Well now, Socrates, with such encouragement from you, it would be a disgrace if a

man did not strive to the utmost to say what he can. So then, it seems to me that whoever

knows something perceives that which he knows. So, for now anyway, it appears that

knowledge is nothing other than perception.

SOCRATES: Spoken nobly and courageously, my boy. That is how you should speak when proclaim-

ing your views. Come on, let us examine it together and whether it happens to be genuine

or a wind-egg. Are you saying that knowledge is perception?

THEAETETUS: Yes.

SOCRATES: Now, it really seems that you have made no ordinary statement about knowledge, but

one that Protagoras

also made, though he said the same things in a somewhat different

way. He says, as you know, that man is the measure of all things: of those that are, that they

are, and of those that are not, that they are not. Indeed, I presume you have read this?

THEAETETUS: Yes, I have read it many times.

SOCRATES: Does this not somehow mean that, in each case, as something appears to me, so it is for

me, and again, as it appears to you, so it is for you – you and I being ‘man’.

THEAETETUS: Yes, this is what it means.

SOCRATES: Now, a wise man is not likely to talk nonsense, so let us follow his argument. Is it true

that sometimes when the same wind is blowing, one of us may be cold while the other is

not, or one of us a little cold while the other is very cold?

THEAETETUS: Of course.

SOCRATES: Now, at that time, can we say whether this wind, in itself, is cold or not? Or should we

accept from Protagoras that it is cold for the person who feels cold, but not for the person

who doesn’t?

THEAETETUS: It seems we should.

SOCRATES: And is that how it appears to each person?

THEAETETUS: Yes.

SOCRATES: But does ‘it appears’ mean ‘it is perceived’?

THEAETETUS: It does.

SOCRATES: Then appearance and perception are the same in the case of warmth, and all such mat-

ters. Indeed, how things are perceived is how things are likely to be for each person.

THEAETETUS: So it seems.

SOCRATES: So, perception is always of what is, and it is not false since it is knowledge.

THEAETETUS: So it appears.

SOCRATES: Well then, by the Graces, was Protagoras an utterly wise person who spoke this riddle

to us common crowd while he divulged the truth

to his disciples in secret?

THEAETETUS: Whatever do you mean by that, Socrates?

SOCRATES: I shall tell you, and this is surely no ordinary account. It states that nothing just by itself

is one, nor may you correctly refer to it as some thing, nor as any kind of thing. But if you

say it is large, it will also appear to be small; and if you say it is heavy, it will also appear

light; and so it is for everything, because nothing is one, or some thing, or of a particular

151 e

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THEAETETUS – 151e–152d | 163

–––––

Aristides II was the grandson of a famous Athenian military and political leader of the same name. His education by

Socrates is part of the subject matter of Plato’s Laches.

Socrates describes his daimon as the usual sign that comes to him and always holds him back from something he is

about to do. Plato, Apology 31c-e, 40a-c, 41d.

Prodicus, a contemporary of Socrates, was a distinguished sophist from Ceos who taught semantics and rhetoric. He

is portrayed in Plato’s Protagoras, and is mentioned in quite a few of Plato’s other dialogues.

Protagoras of Abdera was a renowned sophist who taught rhetoric and virtue, and wrote several books. He is depicted

extensively in Plato’s Protagoras.

This seems to have been the title of one of Protagoras’ books.

Theaetetus, David Horan translation, 6 Nov 25

kind. In fact, everything arises from movement and change and intermingling, and we actu-

ally say that these things are, but we are not referring to them correctly, for nothing ever is,

but is always becoming.

The entire tradition of the wise, except Parmenides, also agrees about this, including

both Protagoras and Heraclitus, and Empedocles and the supreme poets from each branch

of poetry – Epicharmus of the comic, and Homer of the tragic.

And when Homer said,

“Ocean is the source of the gods, and Tethys is their mother”,

he meant that everything is

born from flux and change. Or don’t you think this is what he meant?

THEAETETUS: I do, indeed.

SOCRATES: Is there anyone who could do battle against such a vast army, with Homer as their gen-

eral, and not become a laughing stock?

THEAETETUS: That would not be easy, Socrates.

SOCRATES: It would not, Theaetetus, as there are also the following cogent indications that the

account is correct, since movement produces becoming and what seems to be, while inac-

tivity produces non-being and destruction. Indeed, heat and fire, which actually generate

and regulate everything else, are themselves generated from movement and friction, and

these are both activities. Aren’t these the origins of fire?

THEAETETUS: They certainly are.

SOCRATES: And, indeed, the race of living creatures is sprung from the same processes.

THEAETETUS: It must be.

SOCRATES: And isn’t the condition of our bodies corrupted by inactivity and idleness, but preserved

for the most part by exercise and movement?

THEAETETUS: Yes.

SOCRATES: And what of the condition of the soul? Isn’t it through instruction and attention, which

are activities, that it acquires learning and is preserved and becomes better, while through

inactivity, which is both lack of attention and ignorance, it does not understand anything

and forgets whatever it does understand?

THEAETETUS: It certainly does.

SOCRATES: So, activity is good for both body and soul, while inactivity is the opposite.

THEAETETUS: So it seems.

SOCRATES: I can tell you more about such matters as absence of wind and calm seas, where the

stillness decays and corrupts things, while different conditions will preserve them. But in

addition to this, the ultimate evidence I bring forward is the golden cord that Homer declares

to be the very sun itself, and he explains that as long as the heavens and the sun are in

motion, all things are, and are preserved among both gods and men. However, should this

cease and be tied down, everything would be destroyed, and as they say the world would

be turned upside down.

THEAETETUS: Yes, Socrates, it seems to me that that is exactly what he is explaining.

SOCRATES: Therefore, my friend, you must appreciate to begin with that in the case of the eyes,

what you refer to as white colour is not something separate outside of your eyes, nor is it

in your eyes, nor should you assign any location to it, for it would then be abiding in that

place and would not be in the process of becoming.

THEAETETUS: But how does it work?

SOCRATES: Let us pursue the current argument by proposing that nothing just by itself is one. And

thus it will be evident that black or white or any other colour has arisen from the eyes hitting

upon the relevant motion. Indeed, each so-called colour will be neither that which strikes

nor that which is struck, but something that has arisen in between, private to each. Or would

you maintain that each colour appears to you just as it does to a dog, or any other animal?

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164 | THEAETETUS – 152e–154a

THEAETETUS: By Zeus, I would not!

SOCRATES: What about this? Does anything at all appear similar to you and to another person? Are

you certain of this? Or are you even more certain that it does not appear the same even to

yourself, because you are never in the same state as yourself?

THEAETETUS: That’s even truer than your first example.

SOCRATES: Now, if whatever we measured ourselves by, or touched, was large or white or hot, it

would never become different through encountering something else, unless it itself actually

changed. But on the other hand, if whatever is measuring or touching was large or white or

hot, it would not have become different when another thing drew near or underwent some

process, while nothing happened to itself. As things stand now, my friend, we are forced so

easily into extraordinary and comical utterances, as Protagoras, and anyone who tries to

make the same point as he does, would maintain.

THEAETETUS: What sort of utterances do you mean?

SOCRATES: Take a simple example, and you will know all that I have in mind. Presume there are

six dice and you introduce four dice beside them. We say that they are more than the four,

indeed one-and-a-half times the four. However, if you introduce twelve dice, the six will

be fewer, in fact half of twelve, and that is the only acceptable description. Or would you

accept any other?

THEAETETUS: I would not.

SOCRATES: Well then, what if Protagoras or someone else were to ask you, ‘Theaetetus, is there

any way for something to become bigger or more numerous, other than by being increased?’

What would be your response?

THEAETETUS: Socrates, if I were to give my immediate opinion on this question, I would answer

that it is not possible. But based on your previous question, being wary of contradicting

myself, I would say that it is possible.

SOCRATES: By Hera, my friend, a good and divine response. However, it seems that if you do say

that this is possible, the consequences of Euripides’ words will befall you, for your tongue

will be beyond refutation, but your heart will not.

THEAETETUS: True.

SOCRATES: Now, if you and I were clever and wise, and had searched all the contents of our hearts,

we would now spend the remaining time probing the abundant resources at our disposal, as

we joined in some sort of sophistical contest, banging our arguments against one another.

But now, seeing that we are common men, we shall first prefer to review, in their own terms,

the exact thoughts that we ourselves are thinking, and whether they seem to us to be con-

cordant with one another or entirely discordant.

THEAETETUS: Yes, certainly, I would prefer that.

SOCRATES: And so would I. Now since that is so, shall we examine ourselves faithfully and

patiently, considering once more what these appearances within us actually are? On con-

sidering the first of them, I believe we shall say that nothing would ever become greater or

lesser, either in bulk or numerically, as long as it is equal to itself. Isn’t this the case?

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THEAETETUS – 154b–155a | 165

–––––

Parmenides from Elea in Italy, Heraclitus from Ephesus in Ionia, and Empedocles from Sicily were all influential

preSocratic philosophers. Epicharmus was a comic poet from Syracuse in Sicily. Homer was a bard and epic poet,

composer of the Iliad and the Odyssey.

Iliad xiv.201, 302.

Iliad viii.17-27. Zeus says he could bind everything in a golden cord and tether it to Mount Olympus, leaving it to

hang in mid-air.

The reference is to Euripides, Hippolytus, line 612. Hippolytus says of an oath he has made but not kept, “my tongue

has sworn, but my mind is unsworn”.

Theaetetus, David Horan translation, 6 Nov 25

THEAETETUS: Yes.

SOCRATES: And the second of them will have us say that if nothing is either added to or removed

from something, it will neither increase nor diminish, but it will remain equal.

THEAETETUS: Yes, certainly.

SOCRATES: And won’t the third have us say that nothing can be what it was not before, without

becoming and a process of becoming?

THEAETETUS: It certainly seems so.

SOCRATES: Now, I believe that these admissions are battling with one another in our soul, whenever

we discuss the matter of the dice, or whenever we say that I, who at my age am neither get-

ting bigger nor going in the opposite direction, am now taller than a youth like you, but

later on that I am shorter, over the course of one year. This happens without my frame being

reduced, but through yours becoming bigger. But note that I am, at a later time, what I was

not before, though I have not undergone a process of becoming. But without such a process

it is impossible to become smaller, and without losing any of my bulk I would not have

become shorter. And there are, of course, thousands upon thousands of such instances once

we accept all this. I presume you are following, Theaetetus. You actually seem to have some

familiarity with such issues.

THEAETETUS: I am, Socrates, and by the gods, I wonder intensely what they actually mean. And

the truth is I sometimes get dizzy from looking at them.

SOCRATES: Well, my friend, Theodorus here seems to have made no poor estimate of your endow-

ments. Indeed, this wonder is the particular characteristic of a philosopher, since philosophy

has no other origin than this, and it seems that whoever said that Iris was born from Thaumas

was not a bad genealogist.

But do you now understand why these things are so, based on

the statement we are attributing to Protagoras? Or is it not yet clear?

THEAETETUS: It is not clear to me yet.

SOCRATES: Now, will you feel grateful to me if I assist you in a thorough examination of the truth

hidden in the thought of a famous man? Nay, of famous men?

THEAETETUS: How could I feel anything other than huge gratitude?

SOCRATES: Then look about, and take care lest any of the uninitiated is listening in. These are the

fellows who believe that there is nothing except what they can hold fast with both hands

and do not accept that activities and processes, and all that is unseen, have a share in being.

THEAETETUS: Yes of course, Socrates. You are describing some quite tough and obstinate characters.

SOCRATES: Yes, my boy, they are indeed most ill-educated. But there are others, much more refined,

whose mysteries I am about to reveal to you. Now, their first principle, on which hangs all

we have been discussing just now, is that all is motion and there is nothing else besides this.

The motion has two forms, and each is unlimited in multiplicity, though one has an active

power while the other is passive. From the mutual intercourse and friction of these two with

one another, numerous offspring arise that are limitless in number but always twins. One

twin is the perceptible, and the other is the perception that constantly accompanies the per-

ceptible and is born along with it.

For the perceptions, then, we have such names as seeings and hearings, smellings,

cold and hot, and of course pleasures and pains, desires and fears, as they are called, and

others. Indeed, those without names are innumerable, and those that have been given names

are very numerous. On the other hand, the category of perceptibles has, in turn, a common

origin with each of the perceptions, so with variegated seeings there are variegated colours,

and the same applies to hearings and sounds, and for the other perceptions the other kindred

perceptibles arise. Now, Theaetetus, what does this story tell us about the previous subjects?

Can you see?

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166 | THEAETETUS – 155b–156c

THEAETETUS: Not very well, Socrates.

SOCRATES: Well, let us see if we can bring it to a conclusion. It does indeed mean, just as we are

saying, that all things are in motion, though some are quick in their movements and others

are slow. Now, anything slow has its motion in the same place and relative to whatever

comes near, and it produces offspring in this way. But whatever is produced is quicker, and

moves from place to place, and its motion naturally involves a place to place movement.

Therefore, whenever an eye and something that can be evaluated by it draw near

and generate whiteness and its associated perception – neither of which would ever have

arisen if either of them had encountered something different – there is movement between

them at that time. This movement is sight on the part of the eyes, and whiteness on the part

of whatever joins in the production of the colour. So the eye becomes full of sight, and then

it sees and becomes not sight but a seeing eye, while its partner in the production of colour

is saturated in whiteness and becomes, for its part, not whiteness but something white, be

it wood or stone or anything else that happens to be coloured with a colour of this sort.

And this is actually how things work in general. Hard and hot and all else should be

understood in the same way, to be nothing just by itself, as we were saying before, but in

their mutual intercourse everything of every kind arises from the movement, since there is

actually no firm basis for thinking that the active or passive is something in isolation. For

there is not an active until it is joined to a passive, nor a passive until it is joined to an active.

And that which joins one thing and is active turns out to be passive when it encounters

something else. And the consequence of all this, just as we were saying at the beginning, is

that nothing just by itself is one, but is constantly coming into being with something, and

‘to be’ should be entirely removed from use, not that we have not been compelled to use it

just now, through habit and ignorance.

But the account of these wise men says we must not do this, nor should we accept

the word ‘something’ or ‘of something’ or ‘mine’ or ‘this’ or ‘that’ or any other name that

would make it fixed. Instead we should declare, in accord with nature, that they are coming

into being, being produced and being destroyed or changed, since if anyone fixes anything

with a word, whoever does this will be easily refuted.

This is also how we should refer to particulars and to aggregates of many, aggregates

that are designated as ‘man’ or ‘stone’, and each living creature and form. Now, Theaetetus,

don’t you think this is delightful, and so delicious that you could eat it?

THEAETETUS: Well, I don’t know, Socrates. Indeed, I cannot understand you, and whether you

believe what you are saying or testing me.

SOCRATES: My friend, you are forgetting that I know nothing of such matters, nor do I regard them

as my own offspring, since I am barren. However, I am acting as midwife to you, and on

this account I am charming you, and offering pieces of wisdom for you to taste until I draw

out that belief of yours into the light. Once it is out, I shall evaluate whether it shows itself

to be a wind-egg or a genuine birth. So take heart, and persist! Answer truly and coura-

geously, and tell us how things appear to you, no matter what I ask you about.

THEAETETUS: Very well, ask me.

SOCRATES: Then tell me if you agree that nothing is good or beautiful, or anything else we just

mentioned, but is constantly becoming so.

THEAETETUS: Well, I think so, since it appears marvellously reasonable when I hear you describing

it like this, and it should be accepted exactly as you have recounted it.

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THEAETETUS – 156d–157d | 167

–––––

Hesiod, Theogony 265. Thaumas means ‘wonder’, and Iris is the personification of the rainbow and a messenger of

the Olympian gods.

Theaetetus, David Horan translation, 6 Nov 25

SOCRATES: In that case, let us not leave out anything that is missing from it. What is missing is

consideration of dreaming, diseases in general, and also madness, and the extent to which

we are said to err in hearing and seeing and in our other perceptions. Indeed, you know that

in all these cases the account we gave just now seems to be proved wrong by common con-

sent, as false perceptions certainly arise in us under such circumstances, and so for each

person the appearances are far removed from what is. Rather, on the contrary, nothing at

all that appears to be, is.

THEAETETUS: What you say is perfectly true, Socrates.

SOCRATES: Well then, what argument is left for the one who proposes that perception is knowledge,

and that for the person to whom they appear, whatever appears to be, is, in each case?

THEAETETUS: Well, Socrates, I hesitate to say that I don’t know what to say, since you rebuked me

for saying that just now. Yet the truth is that I could never dispute that madmen and dreamers

have false opinions, when one group believes they are gods, or the others, in their sleep,

think that they have wings and are flying.

SOCRATES: Are you not aware of a similar dispute about these, and about sleeping and waking in

particular?

THEAETETUS: What sort of dispute?

SOCRATES: It is a question that I believe you have heard asked many times. What proof could

you provide if someone were to ask, right now, whether we are asleep at present and are

dreaming everything that we are thinking, or awake and talking to one another in the

waking state?

THEAETETUS: Yes, indeed, Socrates, I am at a loss as to what sort of proof should be provided since

they both correspond so closely, just like mirrored dance movements. Indeed, there’s no

reason why our present conversation couldn’t be a discussion with one another imagined

in sleep. And, of course, whenever we are asleep, and imagine we are recounting dreams,

the resemblance of one to the other is uncanny.

SOCRATES: You see then that there is plenty of room for dispute, when it is even disputed whether

we are awake or asleep! And, indeed, as we spend a similar amount of time asleep and

awake, in either state our soul contends that the opinions held at that time are completely

true. Consequently, we spend an equal time asserting that this realm is real, and we are

equally confident in each case.

THEAETETUS: Entirely so.

SOCRATES: Doesn’t the same argument apply to madness and disease, except that the durations are

not equal?

THEAETETUS: Correct.

SOCRATES: Well then, is truth to be determined by longer or shorter duration of time?

THEAETETUS: That would be entirely ridiculous.

SOCRATES: Well, have you any other obvious way of demonstrating which of these sets of opinions

are true?

THEAETETUS: I don’t think so.

SOCRATES: Then you can hear from me how people talk about these matters when they designate

the appearances of the moment as true for the person to whom they appear. I believe they

would ask a question such as, “Theaetetus, would something that is completely different

have the same capacity as that from which it is different? And let us not assume that we are

asking about something that is the same in one respect but different in another. No, this is

completely different.”

THEAETETUS: In that case, it cannot have anything that is the same, either in capacity or anything

else whatsoever, once it is altogether different.

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SOCRATES: Now, must we not concede that such a thing is also unlike?

THEAETETUS: Well, I think so.

SOCRATES: And if it happens to become like or unlike something, either itself or another, shall we

say that in becoming like, it is becoming the same, while in becoming unlike, it is becoming

different?

THEAETETUS: It must be so.

SOCRATES: And didn’t we say before that there are many – indeed, unlimited – active elements,

and that the same applies to passive elements?

THEAETETUS: Yes.

SOCRATES: And also that anything that is paired with one thing and then with another will not pro-

duce the same things but different things.

THEAETETUS: Yes, certainly.

SOCRATES: Now, let us discuss me and you and things in general, based upon the same argument.

Take Socrates when healthy and Socrates when ill. Shall we say they are like one another

or unlike one another?

THEAETETUS: Are you referring to the unhealthy Socrates as a whole compared to the healthy

Socrates as a whole?

SOCRATES: You have understood perfectly. I mean just that.

THEAETETUS: Then of course they are unlike.

SOCRATES: And is he different then to the extent that he is unlike?

THEAETETUS: He must be.

SOCRATES: And will you say the same about Socrates asleep, and in all the other conditions we

mentioned just now?

THEAETETUS: I think so.

SOCRATES: Now, will each of the things whose nature is to act upon something else treat me in one

way when it encounters healthy Socrates, and in a different way when it encounters

unhealthy Socrates?

THEAETETUS: Inevitably.

SOCRATES: Then is it the case that I who am passive, and this active, will produce different outcomes

in each case?

THEAETETUS: Indeed.

SOCRATES: So when I drink wine when healthy, would it appear pleasant and sweet to me?

THEAETETUS: Yes.

SOCRATES: Indeed, based upon what we agreed before, the active and the passive, both moving

simultaneously, produce both sweetness and perception. Since perception is associated with

the passive, it turns the tongue into something that perceives, while the sweetness associated

with the wine moves about it and makes the wine both appear sweet and be sweet to the

healthy tongue.

THEAETETUS: Yes. What we said before certainly concurs with this.

SOCRATES: But when it encounters the unhealthy Socrates, is that in truth someone different, and

not the same person? Indeed, it approaches something that is unlike the first.

THEAETETUS: Yes.

SOCRATES: Now, a Socrates such as this, along with the draught of wine, gives rise to different out-

comes, a perception of bitterness in the region of the tongue, while in the region of the wine,

bitterness arises and moves, and so the wine becomes not bitterness but bitter, while I

become not perception but a perceiver.

THEAETETUS: Yes, indeed.

SOCRATES: So, I shall never come to perceive any other thing in this way, for there is another

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THEAETETUS – 159b–159e | 169

Theaetetus, David Horan translation, 6 Nov 25

perception of the other thing, and this makes the perceiver different, and different in kind.

Nor would that which is active towards me ever produce the same thing, or itself be the

same sort of thing, in its encounter with something different. For having produced another

from another, it will become different in kind.

THEAETETUS: This is so.

SOCRATES: Nor indeed shall I become such a perceiver by myself, nor will the active element

become different by itself.

THEAETETUS: No, it will not.

SOCRATES: No. But whenever I come to be perceiving, I must be perceiving something, for it is

impossible to come to be perceiving and yet be perceiving nothing. And whenever sweet

or bitter or such like arise, they must arise for some person, for it is impossible to become

sweet, but sweet to no one.

THEAETETUS: Entirely so.

SOCRATES: What remains for us then, I believe, is that if we are, we are for one another, and if we

become, we become for one another, since in fact necessity conjoins our being, yet it binds

us to none of the others, or even to ourselves. So it leaves us bound to one another.

Consequently, if someone says that something is, or becomes, he should say that ‘it is or

becomes for someone’ or ‘of something’ or ‘in relation to something’. But he should never

say, nor allow someone else to say, that it is or becomes just by itself. That is what the argu-

ment we have been expounding indicates.

THEAETETUS: Entirely so, Socrates.

SOCRATES: Now, since whatever is active towards me, is for me and for no one else, mustn’t I also

perceive it and no one else?

THEAETETUS: It must be so.

SOCRATES: So, my perception is true for me, for it always belongs to what I am, and as Protagoras

says, I am judge of the things that are for me, that they are, and also of the things that are

not, that they are not.

THEAETETUS: So it seems.

SOCRATES: Now, if I am not being deceived or erring in my thinking about things that are, or things

that become, how could I fail to have knowledge of the things that I perceive?

THEAETETUS: There is no way this could happen.

SOCRATES: Knowledge is nothing other than perception. That was an excellent saying of yours! So

the various accounts turn out to be the same. Homer and Heraclitus and all their tribe say

everything changes like a flowing stream; Protagoras, the wise, says man is the measure of

all things; and now Theaetetus says that since these things are so, knowledge turns out to

be perception. Is this so, Theaetetus? Shall we declare that this is like your newborn baby,

which I have brought to birth? What do you say?

THEAETETUS: It must be so, Socrates.

SOCRATES: So, it seems that this is what we have at last produced with some difficulty, whatever

it turns out to be. After the birth comes its infant ceremony, and we should faithfully carry

it around the hearth

in the circle of discussion, on the lookout lest the offspring be unwor-

thy of rearing, since it is false and a wind-egg. Or do you believe that your offspring should

be reared in any case, and not be set aside? Could you endure seeing it tested in argument,

and not get violently angry if someone were to take away this, your first-born?

THEODORUS: Socrates, Theaetetus will endure, for he is not at all bad-tempered. But by the gods,

do tell us exactly why this is not the case.

SOCRATES: You are a veritable lover of discourse, Theodorus, and it is kind of you to believe that

I am some bag of arguments and will easily pull one out to explain that all this is not the

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170 | THEAETETUS – 160a–161b

case after all. But you do not understand what is going on, that none of these arguments

ever comes forth from me, but from the one who is conversing with me, and I know nothing

more than the little matter of how to take some argument from someone wise and receive

it appropriately. This is what I shall now try to test from this young man, while I myself

proclaim nothing.

THEODORUS: You are putting that very well, Socrates. Go ahead and do as you say.

SOCRATES: Now, Theodorus, do you know what amazes me about your friend, Protagoras?

THEODORUS: What is it?

SOCRATES: Well, in general I am very pleased with his statement that for each person, what seems,

also is. However, I wonder why he did not say at the beginning of ‘Truth’ that pig is the

measure of all things, or baboon, or some other more unusual creature that has perception,

is the measure. He could then have begun to speak to us grandly and contemptuously,

demonstrating that while we admired him for his wisdom, like a god, he was actually no

more intelligent than a tadpole, let alone another human being. How else can we express

this, Theodorus? For if the opinions formed through perception are indeed true for each

person, and no one judges a person’s experience better than himself, nor is anyone superior

in deciding if the opinion of another is right or wrong, but as we have said many times,

each person is himself the sole judge of his own affairs, and all these opinions are right

and true, what, my friend, is the status of wise Protagoras? Does he properly deserve to be

the teacher of others, for huge fees, and should we, in our relative ignorance, have recourse

to Protagoras when each of us is himself the measure of his own wisdom? Should we con-

clude that Protagoras is saying all this in a popularist vein? I am staying quiet about myself

and my art of midwifery for fear of the ridicule we shall incur, as will the conduct of dialec-

tic in its entirety. For it is a vast and vain pursuit, is it not, to undertake the scrutiny and

refutation of each other’s notions and opinions, if the ‘Truth’ of Protagoras is true and each

of us is right, and this truth is not a jest uttered from the inner sanctuary of the book.

THEODORUS: Socrates, as you said just now, Protagoras was my friend, so I could not bear to co-

operate in his refutation. Nor, however, could I oppose you, contrary to my own opinion.

So involve Theaetetus once more. He seemed to be responding very appropriately just now.

SOCRATES: Well, Theodorus, if you were to go to Sparta, would you have the right to watch other

men, some quite paltry, exercising naked in the wrestling schools and not undress yourself

and expose your own form alongside theirs?

THEODORUS: But why ever not, if they were prepared to trust me and be persuaded by me? Just as

I think that I shall persuade you now to let me watch and not drag me into the gymnasium,

stiff with age, when you can wrestle with a younger, healthier man.

SOCRATES: Well, Theodorus, whatever pleases you does not displease me, as the proverb says, and

so we should go back again to wise Theaetetus. First, Theaetetus, tell us about what we

were saying just now, and whether you are surprised at suddenly proving to be just as wise

as anyone else, whether man or god. Or would you say that the Protagorean measure applies

any less to gods than to humans?

THEAETETUS: By Zeus, I would not. And to answer your question – yes, I am very surprised. Indeed

when we recounted how men argue, when they assert that whatever seems, also is, for the

person who thinks so, this sounded very good to me, but now the very opposite suddenly

turns out to be the case.

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THEAETETUS – 161c–162d | 171

–––––

This is, in essence, the dictum attributed to Protagoras at 152a, with the addition of ‘for me’.

Once a newborn baby reached five days old, it was carried round the family hearth as a symbolic introduction to the

household gods and a request for their protection.

Theaetetus, David Horan translation, 6 Nov 25

SOCRATES: Well, you are young, dear boy, so you listen intently to common talk and you believe

it. Indeed, Protagoras or any of his spokesmen will reply to these arguments and say, “Noble

youths and elders, you sit together indulging in common talk and you bring in the gods,

whose existence or non-existence I exclude from my discourses and from my writings.

And you say things that the multitude would accept when they hear them, like how terrible

it would be if every person differed not in wisdom from the cattle in the fields. But proof

and necessity never enter your pronouncements, and you rely on likelihood.” Yet, if

Theodorus, or some other geometer, decided to use this method in geometry, he would not

be worth one jot. So, in such important matters as these, both you and Theodorus must con-

sider whether you will accept arguments based on persuasiveness and likelihood.

THEAETETUS: No, it’s not right, Socrates. You would not say so, and neither would we.

SOCRATES: Then it seems we should think in a different way, based on the word of yourself and

Theodorus.

THEAETETUS: A different way. Yes, certainly.

SOCRATES: So, let us consider, in this different way, whether knowledge and perception are the

same or different. Indeed, our entire discussion has somehow been dealing with this ques-

tion, and for the sake of this we set in train this plethora of strange topics. Is this not true?

THEAETETUS: Entirely so.

SOCRATES: Shall we agree then that whatever we perceive by seeing or hearing is also known at

the same time? In the case of foreigners, before we learn their language, shall we either

maintain that we do not hear them when they speak or that we hear them and know what

they mean? Or again, if we look at writing with no knowledge of it, shall we assert that we

do not see it or that we know it if we actually see it?

THEAETETUS: Socrates, we shall say that we know this about them anyway, what we see and hear.

Their form and their colour are both seen and known, while high and low pitch are heard

and also known at the same time. But whatever the scribe or the linguist teaches about these,

we neither perceive by seeing nor by hearing, nor do we know it.

SOCRATES: Excellent, Theaetetus, and it is best not to argue that point with you in order that your

development may continue. But look, there is another issue looming. Figure out how to

keep this one at bay.

THEAETETUS: What sort of issue?

SOCRATES: Something like this. If someone were to ask, “Suppose someone comes to know some-

thing at a certain time and still retains and preserves memory of that very thing, is it possible

for him not to know it when he is remembering that very thing?” It seems I am being very

long-winded, when I just want to ask if someone who has learned something could be

remembering it, but not know it.

THEAETETUS: How could he, Socrates? What you are describing would be bizarre.

SOCRATES: Am I talking nonsense then? But consider this. Don’t you say seeing is perceiving, and

sight is perception?

THEAETETUS: I do.

SOCRATES: And someone who has seen something has acquired knowledge of that which he has

seen, according to what we said just now.

THEAETETUS: Yes.

SOCRATES: What about this? Do you agree that there is such a thing as memory?

THEAETETUS: Yes.

SOCRATES: And is it memory of nothing or of something?

THEAETETUS: Of something surely.

SOCRATES: Of things one has learned or perceived. Isn’t it memory of things of this sort?

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THEAETETUS: What else could it be?

SOCRATES: Does a person, on occasion, remember what he has seen?

THEAETETUS: He remembers.

SOCRATES: And does he forget it when his eyes are closed?

THEAETETUS: What an odd thing to say, Socrates!

SOCRATES: Yet we must say so if we are to salvage our previous argument, otherwise it is eliminated.

THEAETETUS: Yes, by Zeus, that’s what I suspect too. But I don’t quite understand why, so you

tell me.

SOCRATES: Well, we say that whoever is seeing comes to have knowledge of that which he is seeing,

for we have agreed that sight, perception and knowledge are the same.

THEAETETUS: Yes, indeed.

SOCRATES: And yet the person who sees, and has come to have knowledge of what he has seen,

does not see it when his eyes are closed though he does remember it. Is this so?

THEAETETUS: Yes.

SOCRATES: But ‘does not see’ is the same as ‘does not know’, if in fact ‘to see’ is ‘to know’.

THEAETETUS: True.

SOCRATES: So, it turns out that someone who has come to know something, and still remembers

it, does not know it since he does not see it. And we said it would be bizarre if this were

the case.

THEAETETUS: What you say is very true.

SOCRATES: Then an impossible conclusion appears to follow if someone says that knowledge and

perception are the same.

THEAETETUS: So it seems.

SOCRATES: So, we have to say that they are different.

THEAETETUS: Very likely.

SOCRATES: Well in that case, whatever is knowledge? It seems we must discuss this again from the

beginning. But, Theaetetus, what on earth are we trying to do?

THEAETETUS: What are you referring to?

SOCRATES: We seem to me like uncouth fighting cocks that turn away and start to crow before we

have won a victory over this argument.

THEAETETUS: How do you mean?

SOCRATES: We seem to be satisfied that we have defeated the proposition by coming to an under-

standing, quite argumentatively, about the similarities between words. We claim to be

philosophers, not debaters, yet we behave unconsciously just like these clever fellows.

THEAETETUS: I still do not understand what you are saying.

SOCRATES: Well, I shall try to clarify my own thoughts on the matter in any case. Now, we were

asking if someone who has learned something and is remembering it could fail to know it,

and we took the example of a person who has seen something and closed his eyes and is

remembering it. We demonstrated that he does not know, and at the same time is remem-

bering, and we said that that is impossible. And so, the Protagorean story met its downfall,

and yours too – your statement that knowledge and perception are the same.

THEAETETUS: So it appears.

SOCRATES: My friend, I believe this would never have happened if the father of that other proposal

were alive, since he would have defended it in all sorts of ways. But now we are mistreating

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THEAETETUS – 164a–164e | 173

–––––

This is a reference to Protagoras’ statement: “Concerning gods I am unable to know whether they exist or do not exist,

or what they are like in appearance; for there are many hindrances to knowledge, the obscurity of the subject and the

brevity of human life”. Diogenes Laërtius, Lives of Eminent Philosophers ix.51.

Theaetetus, David Horan translation, 6 Nov 25

his orphan, and even the trustees left by Protagoras have no desire to help it, Theodorus here

being one of them. Well then, for the sake of justice, we ourselves must come to its aid.

THEODORUS: Yes, Socrates, since I was not Protagoras’ trustee. That was Callias, the son of

Hipponicus.

I somehow turned quickly away from pure discourse and inclined towards

geometry, though I would be grateful to you if you came to his aid.

SOCRATES: Well spoken, Theodorus. Now consider the aid I shall proffer. For we could agree to

even stranger things than before if, in our usual fashion, we do not pay attention to what

we are saying in our affirmations and denials. Shall I explain this to you or to Theaetetus?

THEODORUS: No, explain it to the company. But let the younger man respond to you since he will

be less shamed if he goes wrong.

SOCRATES: Let me then put the most formidable question, that goes something like this: Is it pos-

sible for the same person to know something and not know the thing that he knows?

THEODORUS: Well, what answer shall we give, Theaetetus?

THEAETETUS: Presumably it is impossible, in my opinion anyway.

SOCRATES: Not if you propose that seeing is the same as knowing. For how will you respond to

the inescapable question that, as they say, traps you in a well shaft, when some audacious

fellow puts his hand over one of your eyes and asks if you can see his cloak with that cov-

ered eye?

THEAETETUS: I think I would say that I cannot see it with that eye, but I can see it with the other one.

SOCRATES: So, do you both see and not see the same thing at the same time?

THEAETETUS: Yes, in the way we have described it anyway.

SOCRATES: “That is not the question I put to you,” he will say. “I was asking if you do not know

the thing that you know, regardless of how this occurs. What is not seen now turns out to

be seen, yet you happen to have agreed that seeing is knowing, and not seeing is not know-

ing. Now work out the conclusion from all this.”

THEAETETUS: I am coming to conclusions contrary to what I was proposing before.

SOCRATES: Yes, my friend, and perhaps you would have had more experiences like this, if someone

had gone on to ask you if it is possible to know accurately and dimly, or to know from close

up but not from afar, or know the same thing thoroughly and vaguely. There are lots of

other questions that a combative professional debater, lying in wait, would ask you, once

you propose that knowledge and perception are the same. He would go on to attack hearing

and smelling and all such perceptions, and would keep refuting you relentlessly until you

were in awe of his enviable wisdom and totally entangled by him. And once he had over-

powered you and tied you up, you would be released for a ransom amount that you both

agreed upon.

Perhaps you may ask what argument Protagoras will now proffer in defence of his

own proposition. Shall we try to state it?

THEAETETUS: Yes, certainly.

SOCRATES: Well, no doubt he will say all the things we say in his defence, and I believe he will

also engage in dispute, despising us and saying:

“This Socrates, the simpleton! He tries to argue that I am the one who is ridiculous,

because some little boy is frightened when Socrates asks him if the same person can remem-

ber something and not know it at the same time, and the boy, out of fear, says no because

he cannot foresee the consequences. But the position is as follows, O idle Socrates!

Whenever you investigate any of my propositions through questioning, then I am refuted

only if the person questioned is defeated while answering exactly as I would answer. But if

he answers in another way, it is the actual person questioned who is refuted.

“In this instance, do you think anyone will agree that someone’s present memory of

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174 | THEAETETUS – 165a–166b

things that he experienced is anything like the experience he was having at the time, and is

no longer experiencing? Far from it. Or again, would anyone be reluctant to agree that the

same person can both know and not know the same thing? Or even, if he was afraid of that

proposition, would he ever concede that someone who is becoming unlike is the same as he

was before becoming unlike? Indeed, if he must be on the lookout for the verbal traps that

we each lay, will he ever agree there is a single person, and not a number of persons, and

that these become unlimited, as long as the process of becoming unlike actually continues.

“Dear fellow,” he will say, “come to terms generously with what I actually propose,

and prove if you can that private perceptions are not arising for each of us, or that if the

perceptions that arise are private, what appears is not something that especially arises only

for that person, or ‘is’ for that person, if we must use the word ‘is’.

“Now when you refer to pigs and baboons, you not only act like a pig yourself, but

you persuade your hearers to treat my writings as you do, which is most improper.

“Indeed, I assert that what I have written is the truth, that each of us is indeed the

measure of things that are and are not. However, there are countless differences between

one person and another in this respect, because to one person certain things are and appear,

while to another other things are and appear. I am far from denying that there is wisdom or

a wise man, but the particular man whom I call wise is one who brings about change, and

will make things appear and be good to us, when they both appear, and are, bad. And again,

do not go chasing after this argument based on how I have expressed it, but note this clar-

ification of what I mean. Recall how this was expressed in the earlier conversation, that to

a sick man whatever he eats appears sour and is sour, while the opposite appears to be the

case, and is the case, for a healthy man. Now, we should not portray one as wiser than the

other, nor could we. Neither should we allege that the infirm man is ignorant because he

holds such opinions, nor that the healthy man is wise because his views are different. No,

one condition should be changed to the other because the other is better. And in education

too, we should effect just such a change from one particular condition to a better one. And

while the doctor effects the change with medicine, the sophist does it with his words. Indeed,

no one ever made a man hold true opinions who previously held false opinions, for it is not

possible either to think of things that are not, or of anything outside of what is experienced,

and these are always true. I believe rather that in a degenerate condition of the soul he holds

opinions appropriate to that condition, while in a sound condition of the soul he is made to

hold opinions of a different sort – a set of appearances that some naively refer to as true.

However, I say that one set is better than the other, but not any truer.

“My dear Socrates, I am far from referring to the wise as tadpoles, but when it comes

to the body I call them doctors, and when it comes to plants I call them farmers. Indeed, I

say that these farmers engender sound, healthy and true perceptions in the plants whenever

they are sick, in place of the degenerate perceptions, while the good and wise orators make

whatever is beneficial rather than degenerate seem right to cities. Now, whatever seems

right to each city is good and right for that city, as long as it is believed. But the wise man

makes whatever is beneficial rather than degenerate seem right and be right for them, in

each case. And on the same basis, the sophist is wise, and worth his large fees, as he too

can educate pupils in this manner. And this is how some people are wiser than others while

no one holds a false opinion, and you must put up with being a measure, whether you like

it or not, as the salvation of this argument lies in these assertions.

“Now, if you intend to contradict it all over again, conduct your disputation by

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THEAETETUS – 166c–167d | 175

–––––

Callias III, son of the richest man in Greece, was a student of Protagoras, Prodicus and Hippias, all prominent sophists.

Theaetetus, David Horan translation, 6 Nov 25

presenting a complete argument. Or if you prefer to use questions, then use questions, for

we should not avoid that method either. Indeed an intelligent person should follow that

approach rather than any other.

“However, heed the precept that your questioning be not unjust, as it is very unrea-

sonable that a man who says that he cares about excellence should constantly pursue an

unfair line of argument. Now, it is unfair in this context for someone to carry on this business

without distinguishing between disputation and dialogue. In disputation he may play and

trip up his opponent as often as he can, but in dialectic he should be serious and also set his

partner back on his feet, pointing out to him only those pitfalls into which he has been

misled by himself or his former acquaintances. Once you act in this way, whoever spends

time with you will blame themselves for their confusion and perplexity, and not you. And

they will follow you and love you, and will hate themselves and flee from themselves into

philosophy, so that they may become different people and be freed from what they were

before. But if you do the opposite, as do most people, the consequences will be opposite,

and instead of philosophers you will produce followers who hate the subject once they

become older.

“Now if you listen to me, as I said before, you will settle down, without impatience

and aggression but with a gracious mind, and really consider what precisely we mean when

we proclaim that everything is motion, and that for each person, or city, whatever seems,

also is. And based on this, you will reflect on whether knowledge and perception are the

same or different, but not as you did just now, on the basis of familiar expressions and ter-

minology that many people employ, in whatever manner occurs to them, causing endless

confusion to one another.”

Theodorus, this is the best I can do from my slender resources to offer assistance to

your friend, but if the man himself were alive he would have defended his offspring more

expansively.

THEODORUS: You are joking, Socrates. You have defended the man most vigorously.

SOCRATES: It is nice of you to say so, my friend. But tell me, did you note what Protagoras was

saying just now when he reproached us for directing our arguments against a little child

and using childish fear in refuting his views? He accused us of mere cleverness, extolled

‘the measure of all things’, and urged us to be serious about his argument.

THEODORUS: How could I fail to notice that point, Socrates?

SOCRATES: In that case, do you think we should heed his injunction?

THEODORUS: I certainly do.

SOCRATES: You see then that all the people here, except you, are small children. So if we are

going to obey the man, you and I must be serious about this argument, as we ask and

answer one another. Then at least we shall not be accused of boyish sport as we reconsider

the argument.

THEODORUS: What? Surely Theaetetus could follow the scrutiny of an argument better than many

a man with a long beard?

SOCRATES: Not better than you however, Theodorus. So do not presume that I should make every

effort to defend your deceased companion while you do nothing. Come now, my friend,

follow me for a while, at least until we establish whether it turns out that you are the measure

when it comes to diagrams, or whether everyone is just like you, and sufficient unto them-

selves in astronomy and those other subjects in which you are indeed said to excel.

THEODORUS: Socrates, it is not easy for someone to avoid entering into an argument when they are

sitting beside you, and I spoke nonsense just now, saying that you would not force me to

undress and wrestle as the Spartans do, but would leave the decision up to me. No, you are

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176 | THEAETETUS – 167e–169a

inclined to the trickery of Sciron!

Indeed, the Spartans ask you to undress or go away, but

you behave more like Antaeus, for once someone draws near you won’t let him go until

you have undressed him and forced him into a verbal wrestling match.

SOCRATES: Theodorus, you have presented an excellent image for the malady that afflicts me.

However, I am even more stubborn than the characters you mention. Many a Heracles and

Theseus have crossed my path, powerful speakers who have taken me apart, but I shall

never back down at all, such is the awful passion for these exercises that has gripped me.

So do not refuse to enter the ring with me, as you will benefit yourself as well as me.

THEODORUS: I have no argument against this, so lead me wherever you wish. I must fully accept

the destiny you decree in these matters, and submit to being cross-examined. However, I

shall not be able to surrender myself to you beyond what you are proposing.

SOCRATES: Well, that is far enough. Now, there is one thing you must help me to guard against. We

should not slip into a childish form of discussion and be reproached again for this.

THEODORUS: Well, I shall do the best I can.

SOCRATES: In that case, let us take this up again at the same point as before, and see if we were

right or wrong to find fault in and criticise this proposition because it made each person

self-sufficient in intelligence, and made Protagoras concede to us that, in matters of better

and worse, some excel over others, and these are, in fact, wise. Isn’t this where we were?

THEODORUS: Yes.

SOCRATES: Now, if Protagoras himself were actually present and had agreed, and we had not made

this concession on his behalf in order to help him, there would be no need to seek certainty

by resuming the discussion. But now, perhaps, someone will suggest that we lack authority

to agree on his behalf, and that it would be better to agree this particular point fully with

greater clarity, because whether or not this is the case is no small matter.

THEODORUS: What you say is true.

SOCRATES: Then let us get this agreement as concisely as possible from his own argument rather

than anything else.

THEODORUS: How?

SOCRATES: As follows. He says, I believe, that whatever seems also is, for the person to whom it

seems.

THEODORUS: Yes, he does say that.

SOCRATES: So then, Protagoras, we too are describing the opinions of a man, in fact of all men,

and we declare that there is no one who does not believe himself wiser than others in some

respects, while others are wiser in other respects. Indeed, in the greatest dangers, whether

in battle or disease or storms at sea, they will regard those in authority as gods, who are

expected to act as saviours, though their superiority lies in knowledge and in nothing else.

And the entire human race is full of people in search of teachers and leaders for themselves,

for other creatures, and for their activities, while others think themselves capable of teaching

and leading. Now, in all these cases, what else can we say except that the people themselves

believe that there is wisdom and ignorance among them?

THEODORUS: Nothing else.

SOCRATES: Don’t they believe that wisdom is true thought, while ignorance is false opinion?

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THEAETETUS – 169b–170b | 177

–––––

Sciron was a legendary brigand on the coastal road at the Isthmus of Corinth. He had a reputation for kicking travellers

off the cliffs into the sea, where they were eaten by a giant turtle. The hero Theseus, on his way to Athens, dispatched

him in the same way.

Antaeus was reputed to have been a giant who forced all passers-by to wrestle with him. He drew his invincible strength

from the earth, but was finally defeated by Heracles, who lifted him in the air and then crushed him to death.

Theaetetus, David Horan translation, 6 Nov 25

THEODORUS: Of course.

SOCRATES: So what will become of the proposition, Protagoras? Should we say that people always

think what is true, or do they sometimes think what is true and at other times what is false?

Indeed, it seems to follow from either option that people do not always think what is true.

Rather, they think both. Consider this, Theodorus. Would you yourself, or any follower of

Protagoras, be prepared to contend that no one ever believes that someone else is ignorant

and thinks falsely?

THEODORUS: No one would accept that, Socrates.

SOCRATES: And yet this is where the proposition inevitably leads, the proposition which states that

man is the measure of all things.

THEODORUS: How so?

SOCRATES: Whenever you have formed a judgement by yourself, and you present an opinion to

me about something, we should say that this opinion is true for you, based upon Protagoras’

proposition. But don’t the rest of us become judges of your judgement? Or do we decide

that you always form true opinions? Or do thousands who hold different views oppose you

every time, in the belief that your thought and judgement is false?

THEODORUS: They do indeed, by Zeus, Socrates – thousands, and more, as Homer says,

who

inflict all the troubles of mankind upon me.

SOCRATES: What then? Do you like us to say that in this case, you are forming opinions that are

true for you, but false for thousands?

THEODORUS: It seems that this must follow from the proposition.

SOCRATES: And what about Protagoras himself? Mustn’t it follow that if he himself did not believe

that man was the measure, nor did the world in general – which, in fact, it does not – this

truth that the man has written down would be true for no one? However, if he believed it

himself but the majority did not agree, note firstly that insofar as more people disagree than

agree, to that extent it is more not so than so.

THEODORUS: It must, if it is to be so, and not so, based upon individual opinion.

SOCRATES: Secondly – and this is the cleverest aspect – since Protagoras agrees that everyone

thinks things that are, presumably he accepts as true the thinking of those who hold a view

contrary to his own thinking, and they think that Protagoras is speaking falsely.

THEODORUS: Yes, certainly.

SOCRATES: Wouldn’t he be accepting that his own thinking is false, if he agrees that the thinking

of those who believe him to be speaking falsely, is true?

THEODORUS: He must.

SOCRATES: And yet the opponents do not accept that they themselves are speaking falsely.

THEODORUS: No, they do not.

SOCRATES: While Protagoras again agrees that this opinion is true on the basis of what he has

written.

THEODORUS: So it appears.

SOCRATES: Then it will be disputed by everyone, beginning with Protagoras, who adds his own

agreement whenever he concedes that someone who says the very opposite is forming a

true opinion. In that case, Protagoras himself will be accepting that neither a dog, nor any

random person, is the measure of anything which he has not learned. Isn’t this so?

THEODORUS: It is so.

SOCRATES: Well, since it is disputed by everyone, the ‘Truth of Protagoras’ would be true for no

one, neither for the man himself nor for anyone else.

THEODORUS: We are running my old friend too hard, Socrates!

SOCRATES: But it is not actually clear whether we are running along the right course. Now, it is

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178 | THEAETETUS – 170c–171c

quite likely that the man is wiser than we, since he is older. And if he suddenly popped his

head up from below, as far as the neck, he would expose me as talking a lot of nonsense –

yes, that is likely; you too for agreeing with me – and then he would dive back down, dis-

appear and be gone. However, I think that we must accept ourselves just as we are, and

always state how things seem to us. Accordingly, shouldn’t we declare that any person at

all will probably agree that some men are wiser than others, and some are more ignorant

than others?

THEODORUS: Well, I think so anyway.

SOCRATES: Yes. The best way to establish the argument is by means of the addition we made as we

defended Protagoras. We said that in most cases, such as hot, dry, sweet, and any matters

of that sort, as it seems to each, so it also is for each. However, if the argument is somehow

to concede that one person excels over another in some matters, it will prefer to state that

when it comes to health and disease, it is not every woman, child or beast who is competent

to cure itself and realise what is healthy for itself, but in these cases, if any, one person does

excel over another.

THEODORUS: That is how it seems to me, anyway.

SOCRATES: However, in civic affairs, concerning what is noble and disgraceful, just and unjust,

sacred and profane, whatever each city believes and designates as lawful for itself is, in

truth, lawful for that city. And in these matters, no citizen is wiser than another citizen, nor

is any city wiser than another city. But when it comes to deciding what is advantageous or

disadvantageous for itself, in these cases, if at all, the argument will accept that one adviser

is superior to another, and the opinion of one city is in truth better than that of another, and

would never dare to propose that whatever a city believes to be to its own advantage, and

designates as such, will certainly turn out that way.

But in the cases I referred to before, just and unjust, sacred and profane, people wish

to insist that there is not one of them which by nature has an existence of its own. Instead,

they say that whatever seems so to the people becomes true at the time that it seems so, and

for as long as it seems so. And even people who do not entirely hold to Protagoras’ argument

somehow regard this formulation as wisdom.

Argument after argument is descending upon us, Theodorus, and larger is emerging

from smaller.

THEODORUS: But haven’t we plenty of free time, Socrates?

SOCRATES: It appears that we do, yes. And I have often reflected, my blessed friend, at one time or

another, and indeed just now, that those who spend a lot of time in philosophic pursuits nat-

urally prove to be amusing speakers if they end up in courts of law.

THEODORUS: What do you mean by that?

SOCRATES: Those who have been hanging around law courts and such places from their younger

years will surely seem like slaves rather than free-born men when compared to those brought

up in philosophy and kindred pursuits.

THEODORUS: But in what way?

SOCRATES: In the sense that the philosophers have the free time, which you mentioned, and they

hold their discussions peacefully and in their own time, just as we are doing now, taking up

argument after argument. Indeed, we are already on our third. They can do exactly the same

as us if a new topic interests them more than the current one, and they will not care at all

whether the discussion be long or short, if only they may encounter what is.

But the other sort always speak under pressure of time, from the water that flows

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THEAETETUS – 171d–172e | 179

–––––

Odyssey xvi.121.

Theaetetus, David Horan translation, 6 Nov 25

from the clock,

and they are not allowed to make speeches on matters close to their hearts.

Their opponent stands over them, armed with compulsion and a written document that deals

with every issue, from which they cannot depart. Their words are always about a fellow

slave, addressed to a master who sits with some charge in his hands, and their disputes are

not of a general nature, but the issue is always personal, and his life is often at stake. And

in consequence of all this they become intense and shrewd, knowing how to flatter their

master in words and beguile him in deed, but their souls become small and warped.

Slavishness from youth upwards has removed their growth, uprightness and freedom,

and forced them into crooked ways, casting huge perils and trepidations on their still tender

souls, which they are unable to bear with justice and truth. They turn directly to falsehood

and mutual injustice, and are utterly bowed down and confined. The result is that they turn

out as men who from childhood upwards are devoid of health of mind, though they believe

that they have become clever and wise. So that is the sort of men they are, Theodorus. But

what do you want to say about men of our sort? Do you want us to describe them, or leave

the matter and return again to the argument in case we very much abuse this freedom in

switching between topics that we referred to just now?

THEODORUS: Certainly not, Socrates. I want us to describe them! Indeed, you expressed this very

well. We who move in such circles are not servants to these arguments, but our arguments are

just like our servants, and each of them must wait to be concluded whenever we see fit. Nor,

in fact, is there any jury or audience evaluating or dominating us, as if we were playwrights.

SOCRATES: Well, since that is your view, it seems we should talk about the best of them, for what

could anyone say about the mediocre exemplars of philosophy anyway? But the best of

them, from their early years, do not even know the way to the Agora, nor the whereabouts

of the law courts or the Council Chamber or any other public meeting place in the city.

They neither hear the edicts being proclaimed nor look at the laws when they are written.

They would not even dream of involvement with political parties struggling for power,

alliances, banquets or revelling with flute-girls. Whether someone in the city is high-born

or low-born, or there is some problem with their ancestry, male or female, concerns him no

more than the number of pints in the ocean, as they say. Indeed, he does not even know that

he does not know about these matters, for he does not avoid them for the sake of reputation,

but in truth it is only his body that is situated in the city as a visitor, while his mind regards

all this as small and insignificant, despises it and takes flight, as Pindar says, “above the

heavens and beneath the earth”, measuring the earth’s vast surfaces, studying the stars, and

searching out in every way the complete nature of each whole among the things that are,

never lowering itself to anything that is near at hand.

THEODORUS: What do you mean by this, Socrates?

SOCRATES: One example, Theodorus, is the case of Thales,

who fell into a well as he was gazing

up at the stars, and some clever and witty Thracian maidservant mocked him, saying that

he was so eager to know what was in the sky that he forgot about what was right there under

his feet. Now, the same gibe will apply to everyone whose life is spent in philosophy. Indeed,

such a person will actually be unaware of his next-door neighbour, not only of what the

man does, but even whether he is human at all, or some other creature. What precisely man

is, and what action or response is appropriate to human nature and distinguishes man from

other creatures? This is his search, and these are the questions he is at pains to answer. I

presume you understand now, Theodorus. Do you?

THEODORUS: I do indeed, and what you are saying is true.

SOCRATES: Therefore, my friend, such a person will provide amusement not only to Thracian girls

but to the world in general, when he meets someone privately or in public, as I said in the

173 a

173 b

173 c

173 d

173 e

174 a

174 b

174 c

180 | THEAETETUS – 173a–174c

beginning, and is compelled to discuss matters under his feet or before his eyes, in a court-

room or anywhere else. Through inexperience he falls into wells, and all manner of per-

plexity, and his clumsiness is terrible, giving rise to a reputation for silliness. Of course

when it comes to slander, he has nothing special to say against anyone since he does not

know anything bad about anyone, having never been interested in such matters, and being

at a loss he becomes a figure of fun. When he hears the praises and the proud boasts of oth-

ers, he is conspicuous for his unfeigned, genuine laughter that makes him seem ridiculous.

And, indeed, when a tyrant or king is being praised, he believes he is hearing one of the

stock-keepers, such as a swineherd or shepherd or some dairyman, being congratulated on

a high milk yield, and he thinks that the rulers tend and exploit a more difficult and treach-

erous creature than the stock-keepers, and that his own busyness renders a king as uncouth

and ill-educated within his city walls as any shepherd in a mountain enclosure.

Whenever the philosopher hears that someone has acquired an astonishing amount

of land, as he has acquired thousands of acres or even more, he thinks it but a trifle, as he

is accustomed to viewing the earth in its entirety. And when they sing the praises of families,

as though someone is a nobleman if they have seven wealthy grandfathers to their credit,

he thinks that the speaker is utterly dim, and partial in his view, as his lack of education

renders him unable to see the universal, or to figure out that each person has had countless

thousands of grandfathers and ancestors. Among them, in every case, there were often rich

and poor, kings and slaves, non-Greeks and Greeks, in their thousands. So boasting about

a list of twenty-five ancestors stretching back to Heracles, the son of Amphitryon, appears

remarkably small-minded to him, and he laughs because they cannot banish petty vanity

from their unthinking soul by working out that the twenty-fifth descendant of Amphitryon

was such a man as fate decreed he should be, and the fiftieth will be so too.

Now, in all these cases the philosopher will be derided by the world, partly because

he seems to be above it all, and partly due to his ignorance and perplexity in the particulars

of daily life.

THEODORUS: You are describing the situation very comprehensively, Socrates.

SOCRATES: However, my friend, the philosopher may sometimes draw someone upwards, and the

person may wish, through him, to go beyond “What injustice have I done to you, or you to

me?”, in favour of examining justice and injustice themselves, what each is in itself, and

what distinguishes them from all else and from one another. Or he may go beyond “Is the

king happy?”, “Is a wealthy man happy?”, and enquire into kingship and human happiness

and misery in general, and what sort of states they both are, and the manner in which it is

appropriate for a human being to acquire the one and avoid the other. Now, when that

shrewd and litigious little soul must in turn give an account of all these matters, then the

situation is again reversed. He is dizzy and suspended from on high. Looking down from

the sky above, he is both troubled and perplexed by the strange experience. And his stam-

mering provides no amusement to the girls from Thrace or any uneducated folk, since they

are unaware of his plight. No, he amuses all who have been brought up, not in the manner

of slaves, but the exact opposite.

There they are, Theodorus, the dispositions of the two types of men. One has been

truly brought up in freedom and leisure, and you obviously call him a philosopher, to whom

it is no disgrace to seem simple-minded and of no account when he encounters the menial

174 d

174 e

175 a

175 b

175 c

175 d

175 e

THEAETETUS – 174d–175e | 181

–––––

In law courts and elsewhere, speeches were timed by means of a water clock. Water flowed from one vessel to another

and measured out the desired time.

Thales from Miletus in Ionia was the first of the Greek natural philosophers. He was an engineer, geometer and

astronomer, and was counted among the Seven Sages.

Theaetetus, David Horan translation, 6 Nov 25

tasks of a slave, and does not know how to tidy up bedclothes or make flavoursome food

or a flattering speech. The other type can render all such services efficiently and promptly,

but knows not how to dress like a free man or take the harmony of discourse, and sing the

praises of the life of the gods or of blessed men.

THEODORUS: Socrates, if you were to persuade everyone with your words, as you have persuaded

me, there would be more peace and less trouble among men.

SOCRATES: But evils cannot be eradicated, Theodorus, for there must always be something in oppo-

sition to the good. Neither can they be situated among the gods, but they must haunt the

mortal nature and prowl about the earth. So we should endeavour to flee from here to there

as quickly as we can, and to flee is to be as like unto God as we can, and to be like God is

to become just and holy with the help of wisdom. However, my friend, it is not very easy

to convince people that the reasons we should be pursuing excellence and avoiding vice

are not the reasons the world gives – namely, that we should practise the one and avoid the

other so that we are reputed to be good men and not bad. This actually sounds to me like

the idle talk of old women, as they say. So, we should speak the truth, which is that God is

not unjust in any way whatsoever, but is as just as it is possible to be, and there is no one

more like unto God than the person among us who has, in turn, become as just as possible.

And therein lies the true measure of a man’s accomplishment, and indeed his worthlessness

and inhumanity, for knowledge of this is wisdom and true excellence, while ignorance of

this is folly and manifest vice. Any other seeming accomplishment or wisdom is vulgar in

the case of political sovereignty, and commonplace when it comes to the other arts.

Therefore, it is best by far not to concede to an evildoer, or one whose words or

deeds are unholy, that his roguery is an accomplishment, for they delight in that reproach

and fancy they are hearing not that they are ridiculous burdens to the earth, but men well

fitted for survival in the city. So the truth must be spoken, that they are the sort of people

they believe they are not, and all the more so because they do not believe so. Indeed, they

are ignorant of the penalty for injustice, which is the last thing they should be ignorant of.

For the penalty is not what they think it is, scourging or execution, which offenders some-

times avoid suffering. No, this is a penalty that cannot be avoided.

THEODORUS: What penalty do you mean?

SOCRATES: There are two patterns established in what is – one of divine blessedness, the other of

godless wretchedness – but they do not see that this is how things are. So, through their

foolishness and utter mindlessness, they fail to realise that because of unjust actions they

are becoming like one pattern and unlike the other. So their lives are like the pattern they

resemble, and that is the penalty they pay. But if we should tell them that unless they set

aside their accomplishment, the place that is pure of evils will not receive them when they

die – but they will continue in their own pattern of living, evil men among their own kind

– they will listen to us as though we were mindless folk addressing clever rogues.

THEODORUS: They certainly will, Socrates!

SOCRATES: Yes, my friend, I know. However, there is one thing that happens to them in private

whenever they must present an argument, and accept one in return, about the matters they

disparage, and are prepared to persist manfully for an extended duration without running

away like cowards. Strangely, my dear friend, they end up dissatisfied with what they them-

selves are saying, and their eloquence somehow dries up, so that they seem no different

from children.

Now, let us call a halt, since this is really a digression. Otherwise, the continued

influx of issues will overwhelm our initial discussion. So if you agree, let’s return to the

previous topic.

176 a

176 b

176 c

176 d

176 e

177 a

177 b

177 c

182 | THEAETETUS – 176a–177c

THEODORUS: A digression like this makes quite pleasant listening for me, Socrates, since it is easier

to follow at my age. However, let us go back to the other discussion again if you think fit.

SOCRATES: Well, I believe we were at a point in the discussion at which we said that the people

who declare that being is in motion – and that whatever seems is for the person to whom it

seems – are in general prepared to assert this confidently. And especially in the case of jus-

tice, they state most emphatically that whatever a city regards as just, and decrees to be

just, is just for that city for as long as the decree remains in force. However, when it comes

to what’s good, there is no one so heroic that he would also dare to contend that whatever

a city believes to be beneficial for itself, and decrees to be so, is actually beneficial for as

long as the decree stands, unless he is referring to the mere name. But that would be making

a joke of our discussion, wouldn’t it?

THEODORUS: It surely would.

SOCRATES: Yes, he should not refer to the mere name, but should consider the thing that is being

named.

THEODORUS: Of course.

SOCRATES: But whatever name it is given, a city surely legislates and enacts all the laws with the

aim of maximising the benefit to itself, according to its understanding and ability. Or does

it look to some other factor when it legislates?

THEODORUS: Not at all.

SOCRATES: Now, does each city always succeed, or do they also frequently miss the mark?

THEODORUS: Well, I think they also miss the mark.

SOCRATES: Then again, anyone at all might accept these same points more readily if someone were

to ask about the entire kind to which benefit also belongs, and that, I believe, involves future

time. For whenever we legislate, we enact laws that will be beneficial in time to come, and

this we would properly designate as ‘future’.

THEODORUS: Yes, certainly.

SOCRATES: Come on. Let us question Protagoras in this way, or anyone who says the same thing

he says. “You say, Protagoras, that man is the measure of everything, including white, heavy,

light, and everything like that, without exception. For having the criterion of these within

himself as he experiences them, so he thinks they are, and what he thinks is true for him,

and is so for him. Isn’t this so?”

THEODORUS: Just so.

SOCRATES: “And what about future events, Protagoras? Shall we say that he has the criterion of

these within himself, and that as he thinks they will be, so they also turn out for the person

who thinks so? In the case of heat, suppose a layman thinks he is about to get a fever and

will have a temperature, while his doctor thinks the opposite. Which opinion should we say

that the future will confirm? Or will it confirm both, and for the doctor neither temperature

nor fever will arise in the man, while for the man himself there will be both?”

THEODORUS: That would be ridiculous.

SOCRATES: “Yes, and I think that the farmer’s opinion about wine, rather than the lute-player’s, is

superior regarding the sweetness or bitterness of the future product.”

THEODORUS: Of course.

SOCRATES: “Nor again would the trainer judge better than the musician about what will be discor-

dant or melodious, and what will seem to be melodious even to the trainer himself when he

hears it.”

THEODORUS: Not at all.

SOCRATES: “Or suppose that a meal is being prepared. The judgement of a waiting guest with no

knowledge of cookery is inferior to the judgement of the cook about how pleasant the meal

177 d

177 e

178 a

178 b

178 c

178 d

THEAETETUS – 177d–178d | 183

Theaetetus, David Horan translation, 6 Nov 25

will be. So, let us not dispute about present pleasure or past pleasure for each person at this

stage in the discussion. Let us discuss the future, and whether the person himself is the best

judge of how things will seem, and what will be, and whether you, Protagoras, could at any

rate anticipate better than any amateur, what speeches would be persuasive to any of us in

a courtroom?”

THEODORUS: And, indeed, Socrates, he professed quite strongly to be better than anyone in that

respect anyway.

SOCRATES: Yes, by Zeus, dear friend, otherwise no one would have paid vast sums of money to

talk to him. He must have persuaded them that no prophet, or anyone else, could judge

better than himself how things will be in the future, and how they will seem.

THEODORUS: Very true.

SOCRATES: Well, are legislation and benefit both concerned with the future? And would everyone

agree that when a city legislates it must frequently fall short of obtaining the greatest pos-

sible benefit?

THEODORUS: Yes, indeed.

SOCRATES: So, I think it would be reasonable for us to put it to your teacher that he must agree that

one person is wiser than another, and that such a person is the measure, while I, in my igno-

rance, must not become the measure of anything at all, though the argument, entered on his

behalf just now, compelled me to be a measure whether I wanted to or not.

THEODORUS: I think his argument, Socrates, is defeated convincingly by that, and it is also defeated

by giving authority to the opinions of others, opinions which state that, in their view,

Protagoras’ argument is not true at all.

SOCRATES: An argument like this, Theodorus, that every opinion of every person is true, could be

disproved in many other ways. But it is harder to grasp the untruth of the immediate expe-

rience of each person, from which perceptions and opinions about it arise. But perhaps I

am talking nonsense and these cannot actually be challenged, and those who say that per-

ceptions are self-evident and constitute knowledge may be describing the way things are,

and Theaetetus here was not far wide of the mark in proposing that knowledge and percep-

tion are the same.

So we should get closer and inspect this moving being, as Protagoras’ proxy argu-

ment directs us, and tap it and test whether it rings hollow or true. Anyway, it is no minor

dispute that has arisen over this, and there are quite a few participants.

THEODORUS: Yes, it is far from being minor. In fact, it is spreading all over Ionia, as the followers

of Heraclitus lead the chorus for this argument most vigorously.

SOCRATES: Well, in that case, dear Theodorus, we should consider it all the more from its very ori-

gin, just as they themselves present it.

THEODORUS: Entirely so, Socrates. And in fact you could no more conduct a discussion on these

Heraclitean doctrines, or the Homeric or more ancient ones you mention, with any of the

Ephesians

who profess to be experts, than you could with madmen. Indeed, they simply

keep moving as their doctrines say they should, while staying with a proposition or question,

and quietly asking and answering in turn means less than nothing to them. Well, ‘less than

nothing’ is an exaggeration, but there is no rest whatsoever in these men. Rather, if someone

asks a question, they pull out enigmatic aphorisms like arrows from a quiver and shoot

them off, and if you seek an explanation of something they have said, you get struck with

a new piece of wordplay. You will never make any progress with any of them, nor do they

get anywhere with one another, but they are very careful not to permit anything certain in

an argument, or in their own souls, believing, I presume, that this is fixity, their worst enemy,

which they try as best they can to banish from the world.

178 e

179 a

179 b

179 c

179 d

179 e

180 a

180 b

184 | THEAETETUS – 178e–180b

SOCRATES: Perhaps, Theodorus, you have seen these men when they are being combative, and have

not associated with them when they are at peace. Indeed, they are no friends of yours! But

I think they do impart such matters, at leisure, to the pupils whom they want to make like

themselves.

THEODORUS: By heavens, what pupils? One of these fellows does not become the pupil of another.

No, they grow up as they will and each of them takes inspiration from anywhere at all,

and one man thinks that the other man knows nothing. As I was about to say, you would

never get a rational account from these people, either willingly or under compulsion.

Instead, we must investigate the question ourselves as if we were taking on a mathematical

problem.

SOCRATES: Well, that sounds reasonable at any rate. Haven’t we taken on the problem from the

ancients, who used poetry to conceal from the multitude that the origin of everything else

is Oceanus and Tethys, which are streams, and that nothing is fixed? Don’t we have it

from the moderns, who, being wiser, put on a more open display so that even cobblers

pick up the wisdom of these men and give up their silly belief that some things are at rest

while others are in motion, learn that everything is in motion, and come to respect these

teachers?

But, Theodorus, I had almost forgotten that others, for their part, proclaim opposite

views to these. “All should only be called unmoving”, they say. And there is much else that

the opponents of these doctrines say, when, like Melissus

and Parmenides, they assert that

all is one, established within itself with no place to move in.

So what are we to make of all this, my friend? For moving forward, little by little,

we have unwittingly ended up between the two sides, and if we do not defend ourselves

and escape, we shall pay for it, like men playing in the wrestling ground who are caught by

both sides and dragged in opposite directions across the line. Now, I think we should con-

sider the people we began with, the men of flux, and if they appear to be talking sense, we

shall help them to drag us to their side and try to escape the others. However, if the words

of those who say that all is at rest sound truer, we shall fly to them, away from the men

who move the unmoving. But if they both appear to be unreasonable, we shall be amusing

in our belief that we common folk have something to say, when we have spurned the

ancients and the utterly wise men. Well, Theodorus, do you think it is better to keep going

in the face of such a danger?

THEODORUS: It would be quite unacceptable, Socrates, not to investigate what each of these groups

is saying.

SOCRATES: Let us investigate it since you are so enthusiastic. Now, I think that our investigation of

motion starts by considering the sort of thing people actually mean when they say that all

things are in motion. I want to ask whether they mean there is one form of motion, or, as it

appears to me, two forms. But this should not be my opinion alone. You should join in too,

so that whatever the outcome, we go through the process together. So tell me, when some-

thing changes from one location to another or when it revolves in the same place, do you

call that motion?

THEODORUS: I do, indeed.

SOCRATES: Then let that be one form of motion. But whenever something remains in the same

place, yet grows old or goes from white to black or soft to hard or undergoes some other

alteration, doesn’t that deserve to be called another form of motion?

180 c

180 d

180 e

181 a

181 b

181 c

181 d

THEAETETUS – 180c–181d | 185

–––––

The inhabitants of Heraclitus’ home city of Ephesus.

Melissus, from the island of Samos off the coast of Ionia, was a pre-Socratic philosopher in the tradition of Parmenides.

Theaetetus, David Horan translation, 6 Nov 25

THEODORUS: I think so.

SOCRATES: So I am saying that there are two forms of motion – alteration and transposition.

THEODORUS: And what you say is correct.

SOCRATES: So, having divided motion in this way, let us now engage in discussion with those who

say that all things are in motion, and ask them whether everything exhibits both forms of

motion, transposition and alteration, or do some things exhibit both, while some exhibit

only one?

THEODORUS: By Zeus, I really cannot say, but I believe they would reply that everything exhibits

both.

SOCRATES: Yes, my friend, otherwise for them everything will turn out to be both moving and

at rest, and it will be no more correct to say that all things are moving than all things are

at rest.

THEODORUS: What you say is perfectly true.

SOCRATES: Well then, since they must be in motion, and absence of movement is not possible for

anything, everything is continually exhibiting every kind of motion.

THEODORUS: It must be so.

SOCRATES: Now consider the following aspect of their proposition with me. Didn’t we say that

they propose something like this about the origin of heat and whiteness and the like, that

each of these is moving, along with perception, between the active and the passive, and that

the passive becomes a perceiver, but not perception, while the active becomes something

with a certain quality, but does not become a quality? But perhaps ‘quality’ seems like a

strange term that you do not understand from common usage,

so listen to a few examples.

Indeed, the active element does not become heat or whiteness, but hot or white, and the

same applies to all else. For I presume you recall what we said before, that nothing just by

itself is one, neither an active nor a passive, but from the mutual association of both of

them, perceptions and perceptible things are brought to birth, and the active become things

with qualities while the passive become perceivers.

THEODORUS: I remember. How could I forget?

SOCRATES: So let us set aside whatever else they say, whether it accords with this or not, attend

only to this one topic of our discussion and ask them, “Do you say that all things are in

motion and flux? Is this so?”

THEODORUS: Yes.

SOCRATES: Now are they moving with both motions, which we defined as transposition and alter-

ation?

THEODORUS: They must be, if they are to be completely in motion.

SOCRATES: And if they were only transposed, and not altered, I presume we would be able to say

what sort of things are being transposed in flux, or is this how we should refer to it?

THEODORUS: Yes, this way.

SOCRATES: But since this is not stable either, the flux does not flow white, but changes so that there

is also flux of this very whiteness, and it transforms into another colour lest it be convicted

of being stable in this respect. So how can we ever refer to a colour and call it by its proper

name?

THEODORUS: Yes, how can we do it, Socrates? Or how can we refer to anything else of that kind,

if in fact it is constantly slipping away as we are speaking because it is in flux?

SOCRATES: But what if we ask about any perception at all, like that of seeing or hearing? Does it

ever remain stable as just seeing, or just hearing?

THEODORUS: No, it must not, if in fact all things are in motion.

SOCRATES: So it should no more be referred to as seeing than as not seeing, nor should any other

181 e

182 a

182 b

182 c

182 d

182 e

186 | THEAETETUS – 181e–182e

perception be called perception rather than non-perception, if all things are in every kind

of motion.

THEODORUS: No, it should not.

SOCRATES: And yet, Theaetetus and I have stated that perception is actually knowledge.

THEODORUS: Yes, that is what you said.

SOCRATES: So, when we were asked what knowledge is, we gave an answer that is no more knowl-

edge than not knowledge.

THEODORUS: It seems so.

SOCRATES: The correction to the answer may turn out well for us who were so keen to show that

all things are in motion, so that our original answer would prove to be correct. But now it

seems to be the case that if all things are in motion, every answer that anyone gives on any

subject is equally correct, whether it proclaims ‘this is so’ or ‘this is not so’, or if you prefer,

we could say ‘becomes so’, in case we stabilise these fellows with the word ‘is’.

THEODORUS: What you say is correct.

SOCRATES: Yes, Theodorus, except that I said ‘so’ and ‘not so’. But the word ‘so’ should not be

uttered, for what is ‘so’ is no longer in motion, nor again should we say ‘not so’, for it is

not in motion either. Instead, those who propose this doctrine must establish some other

language, since they do not currently have words appropriate to their hypothesis, unless

perhaps ‘not even thus’, an indefinite phrase, would best suit their purposes.

THEODORUS: Yes, that might well be the most appropriate language for them.

SOCRATES: Well then, Theodorus, we have freed ourselves from your friend and do not yet agree

with him that every man is the measure of all things, unless the man has understanding.

And we shall not concede that knowledge is perception, not on the basis of the ‘all things

are in motion’ approach anyway, unless Theaetetus here has another way of expressing it.

THEODORUS: I am glad you said that, Socrates, for with these issues concluded I too am freed from

answering your questions, as we agreed, since the discussion of Protagoras’ proposition has

come to an end.

THEAETETUS: No, Theodorus, not until Socrates and yourself have dealt with those who assert that

all is at rest, as you proposed earlier.

THEODORUS: Is a young man like you, Theaetetus, teaching his elders to be unjust and break their

agreements? Prepare yourself instead to respond to Socrates for the remainder of the dis-

cussion.

THEAETETUS: I shall, if he wants me to. However, I would much rather listen to the other topic

mentioned.

THEODORUS: Calling Socrates into an argument is like calling cavalry to fight on open ground. So

just ask, then sit back and listen.

SOCRATES: But, Theodorus, I do not think that I shall be persuaded to do what Theaetetus is asking.

THEODORUS: Why won’t you be persuaded?

SOCRATES: I would be ashamed if we gave only cursory consideration to Melissus and the others

who declare that all is at rest, but the shame would be greater in the case of the One –

Parmenides. Parmenides appears to me, in Homer’s phrase, to be at once ‘venerable’ and

‘formidable’.

Indeed, I met the man when I was very young and he was very old, and he

seemed to me to have depth and total nobility.

I am afraid that we may not come to terms

183 a

183 b

183 c

183 d

183 e

184 a

THEAETETUS – 183a–184a | 187

–––––

This is the first usage of the Greek term poiotēs, which literally means ‘what-sort-ness’ but is usually rendered in

English as ‘quality’.

Iliad iii.172; Odyssey viii.22, xiv.234.

This encounter, whether it is historically accurate or not, is depicted in Plato’s Parmenides.

Theaetetus, David Horan translation, 6 Nov 25

with what he said, and that his intention in saying so may escape us all the more. Also, the

major topic that began this discussion – namely, what exactly knowledge is – may go unin-

vestigated if we allow this disordered influx of propositions, especially since the subject

we are now raising is really immense and would not deserve to be investigated as a mere

side issue. However, if we give it what it deserves, it will obscure our discussion about

knowledge. So we should do neither. Instead, we should endeavour, through the midwife’s

art, to deliver Theaetetus of his conceptions about knowledge.

THEODORUS: Well, if that’s what you think, that’s what should be done.

SOCRATES: In that case, Theaetetus, let us consider this additional point in relation to what has been

said. You gave an answer whereby perception is, in fact, knowledge. Is this so?

THEAETETUS: Yes.

SOCRATES: Now if someone were to ask you, “With what does a person see black and white, and with

what does he hear high and low pitch?”, I presume you would say “with eyes and with ears”.

THEAETETUS: I would indeed.

SOCRATES: A laxity in the use of words and phrases without any precise scrutiny is, for the most

part, quite gentlemanly. Indeed, it is the opposite approach that is illiberal, though it is some-

times necessary, as in the present case, where we must take the answer you gave and con-

sider a problem with it. Which answer is more correct, that the eyes are that with which we

see, or by means of which we see? Are the ears that with which we hear, or by means of

which we hear?

THEAETETUS: I think that we perceive by means of eyes and ears, rather than with them.

SOCRATES: Yes, my boy, it would surely be strange if there were lots of senses lodged inside us,

like soldiers in the Wooden Horse, and everything did not converge on some single form,

be it soul or whatever it should be called, with which by means of the senses, as if they

were instruments, we perceive whatever is perceptible.

THEAETETUS: Yes, I think it is better to put it that way, rather than the other way.

SOCRATES: Now, I am being so precise with you about this for the following reason: I want to ask

if there is some part of ourselves that is the same, with which we conclude by means of the

eyes that things are white or black, or by means of the other sense organs that things have

various qualities. If you were asked, would you be able to refer all such processes to the

body? But perhaps it is better that you give the answer to the question rather than me doing

the job for you. So tell me, by means of what do we perceive hot, hard, light and sweet?

Wouldn’t you propose that it is by means of the body that you perceive each of them? Or

is it by something else?

THEAETETUS: Nothing else.

SOCRATES: And are you prepared to agree that whatever can be perceived by means of one faculty

cannot be perceived by means of a different faculty, so you cannot see sounds or hear sights?

THEAETETUS: How could I disagree?

SOCRATES: So, if you think something of both, you could not be perceiving them both through only

one or the other of the sense organs.

THEAETETUS: I could not.

SOCRATES: Now in the case of sound or colour, do you first think this about both of them, that they

both are?

THEAETETUS: I do.

SOCRATES: And then, that each is different from the other, and the same as itself?

THEAETETUS: Indeed.

SOCRATES: And that both together are two, while each is one?

THEAETETUS: That also.

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SOCRATES: And can you also consider whether they are like or unlike one another?

THEAETETUS: Perhaps.

SOCRATES: Now, by means of what do you think all these things about them both? Indeed, whatever

is common to them cannot be apprehended by means of hearing or seeing. And there is also

further evidence for what we are saying, for if it were possible to consider whether both

are salty or not, you know you could say what you would use to investigate this, and that

is evidently neither seeing nor hearing, but something else.

THEAETETUS: Yes, of course, it is the capacity that is exercised by means of the tongue.

SOCRATES: Well expressed! But now, by means of what comes the power to show you what is com-

mon to these, and to everything, including what you refer to as ‘is’ and ‘is not’, and whatever

we were asking about just now? What sort of organ will you assign to all these, by means

of which our perceiving part perceives each of them?

THEAETETUS: You mean being and not being, likeness and unlikeness, same and different, as well

as one, and number in general, associated with them. And obviously you are asking about

odd and even and whatever else is associated with them, and you want to know the physical

organ by means of which we perceive these with the soul.

SOCRATES: You are following excellently, Theaetetus. Those are the very things I am asking about.

THEAETETUS: Well, by Zeus, Socrates, I am quite unable to answer, except that I do not think at all

that their source is some particular organ as in the other cases, but it appears to me that the

soul itself, by means of itself, investigates what is common to them all.

SOCRATES: You are a beauty, Theaetetus, and not ugly as Theodorus said, for he who speaks beau-

tifully is beautiful and good. Indeed, as well as being beautiful, you have done me a favour

by saving me from a lengthy exposition, since it seems to you that the soul investigates

some things itself, by means of itself, and other things by means of bodily powers. That is

actually what I was thinking myself, but I wanted you to think so too.

THEAETETUS: Well, that’s how it appears anyway.

SOCRATES: Now, in which of the categories do you place ‘being’? For it is surely common to every-

thing.

THEAETETUS: I place it among those things that the soul reaches for, just by itself.

SOCRATES: Along with like and unlike, same and different?

THEAETETUS: Yes.

SOCRATES: And what about beautiful and ugly, good and bad?

THEAETETUS: Yes, I think the soul considers the being of these in particular, in relation to one

another, as it reflects within itself upon past and present in relation to the future.

SOCRATES: Hold on! Won’t the hardness of anything hard, and the softness of anything soft, be

perceived by means of touch?

THEAETETUS: Yes.

SOCRATES: But the soul, by reviewing them and comparing them to another, tries to determine for

us their being, that they both are, and their oppositeness to one another, and again, the being

of the oppositeness.

THEAETETUS: Yes, certainly.

SOCRATES: Now as soon as they are born, man or beast is naturally capable of perceiving whatever

experiences are referred to the soul by means of the body. But reflection upon the being of

these, and their benefit, arises gradually over time through much application and education

on the part of those who actually attain it.

THEAETETUS: Entirely so.

SOCRATES: Now, can someone encounter truth who has not even encountered being?

THEAETETUS: Impossible.

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SOCRATES: And if someone does not encounter the truth of something, will he ever have knowledge

of it?

THEAETETUS: How could he, Socrates?

SOCRATES: So knowledge is not in these experiences, but in the process of reasoning about them,

for it seems that we are able to apprehend truth and being in this way, but not through the

experiences.

THEAETETUS: So it appears.

SOCRATES: Well then, should you call them both by the same name when they are so different?

THEAETETUS: No, that would not be right.

SOCRATES: Then what name do you give to the first, to seeing, hearing, smelling and feeling cold

or hot?

THEAETETUS: I call it perception, Socrates. Is there another option?

SOCRATES: So you refer to it collectively as perception?

THEAETETUS: I must.

SOCRATES: And we say it has no share in the apprehension of truth, for it has no share in the appre-

hension of being.

THEAETETUS: No.

SOCRATES: Then, Theaetetus, perception and knowledge could never be the same.

THEAETETUS: Apparently not, Socrates, and now it really has become abundantly clear that knowl-

edge is different from perception.

SOCRATES: But this was not the reason we embarked upon our discussion. Its aim was to find out

what knowledge actually is, not what it is not. Nevertheless, we have made enough progress

not to look for it in perception at all, but in what the soul is engaged in when it is concerned,

just by itself, with things that are, whatever we call it.

THEAETETUS: Yes, Socrates, and I believe this is called forming opinions.

SOCRATES: Yes, your belief is correct, my friend. And now review this again from the beginning.

Wipe all our previous discussion from your mind and see if you have a better perspective

having made this much progress. Say once more what knowledge actually is.

THEAETETUS: Well, Socrates, I cannot say that it is all opinions, since there is false opinion, so

knowledge is most likely to be true opinion. Take that as my answer. However, as we pro-

ceed, if that turns out to be incorrect, as happened just now, we shall try another way of

putting it.

SOCRATES: Now, that is how you should speak, Theaetetus, eagerly, rather than answering hesitat-

ingly as you did at first. For if we act like this, there are two possibilities: either we shall

find what we are pursuing, or be less inclined to think that we know what we do not know

at all, and an outcome like that would actually be no poor recompense. So what are you

saying now? Are there two kinds of opinion, one true and the other false, and do you define

knowledge as true opinion?

THEAETETUS: I do, that’s how it seems to me at the moment.

SOCRATES: Then is it worth taking up an issue concerning opinion?

THEAETETUS: What sort of issue?

SOCRATES: It is somehow bothering me now, and has done so many times before, generating great

perplexity in relation to myself and others, since I am unable to say what precisely this

experience of ours is, and how it arises in us.

THEAETETUS: What are you referring to?

SOCRATES: The formation of false opinion. Thinking about it now, I am even more hesitant as to

whether we should accept it, or investigate it in a different way than we did a while ago.

THEAETETUS: Why not, Socrates, if it seems at all necessary? For what yourself and Theodorus

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190 | THEAETETUS – 186d–187d

said earlier about leisure was quite true, in matters of this sort there is no hurry.

SOCRATES: You are right to remind me, for perhaps this is not a bad time to retrace our steps. Better,

indeed, to accomplish a little and do it well than to do a great deal but do it inadequately.

THEAETETUS: Of course.

SOCRATES: How shall we proceed? What do we actually mean? Are we saying that whenever there

is false opinion, one of us forms a false opinion, while someone else, by contrast, forms a

true one, as this is the natural state of affairs?

THEAETETUS: Yes, that is what we are saying.

SOCRATES: Now, isn’t each and everything we encounter either known by us or not known? Indeed,

at the moment, I am omitting mention of the intermediate states of learning and forgetting,

for they are not relevant to us just now.

THEAETETUS: Well, in that case, Socrates, there is nothing else left in each case, apart from knowing

or not knowing.

SOCRATES: Then whoever forms an opinion must form an opinion, either about what he knows or

what he does not know.

THEAETETUS: He must.

SOCRATES: And, indeed, isn’t it impossible for someone who has come to know something, not to

know that same thing, or for someone who does not know, to know?

THEAETETUS: This must be so.

SOCRATES: So then, does someone who forms false opinions think that things that he knows are

not those things, but different things that he knows, and having known both, does he then

fail to recognise either?

THEAETETUS: No, that would be impossible, Socrates.

SOCRATES: Well, could he think that things that he does not know are other things that he does not

know, and is it possible that someone who knows neither Theaetetus nor Socrates could

take a notion that Socrates is Theaetetus, or that Theaetetus is Socrates?

THEAETETUS: How could he?

SOCRATES: Nor indeed does he think that things he knows are somehow things he does not know,

nor that things he does not know are things that he knows.

THEAETETUS: No, that would be very strange.

SOCRATES: So how could someone ever form a false opinion? For it is impossible to form an opinion

based on anything but these options, seeing that everything is either known or not known,

but based on these considerations, it seems impossible to form false opinion.

THEAETETUS: Very true.

SOCRATES: So then, we should not investigate what we are looking for in this way, on the basis

of knowing and not knowing. Should we proceed instead on the basis of being and not

being?

THEAETETUS: What do you mean?

SOCRATES: Perhaps it is as simple as this. Whoever, on any subject, is thinking things that are not,

will inevitably form false opinions, whatever the general state of his mind may be.

THEAETETUS: Quite likely, Socrates.

SOCRATES: But how? What would we reply, Theaetetus, if someone were to ask, “Is it possible for

anyone to do what you are saying, and is there some person who could think what is not,

either just by itself, or about some of the things that are?” And it seems we would say in

reply, “Yes, whenever he thinks and thinks what is not true.” Is that how we would answer?

THEAETETUS: Just so.

SOCRATES: Now, does that sort of thing happen in any other instances?

THEAETETUS: What sort of thing?

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SOCRATES: Well, that a person sees something yet sees nothing.

THEAETETUS: How could he?

SOCRATES: Well then, if he sees any one thing, he sees something that is, or do you imagine that

one is ever included among things that are not?

THEAETETUS: I do not.

SOCRATES: So a person who sees any one thing, sees something that is.

THEAETETUS: Apparently.

SOCRATES: And so, a person who hears something is hearing some one thing, something that is.

THEAETETUS: Yes.

SOCRATES: And a person who touches something is also touching some one thing, something that

is, since he is touching one.

THEAETETUS: That is also true.

SOCRATES: And doesn’t a person who is thinking, think some one thing?

THEAETETUS: He must.

SOCRATES: And in thinking one thing, he is thinking something that is.

THEAETETUS: I agree.

SOCRATES: So, a person who is thinking what is not, is thinking nothing.

THEAETETUS: So it appears.

SOCRATES: However, a person who is thinking nothing, is not thinking at all.

THEAETETUS: That seems obvious.

SOCRATES: So it is not possible to think what is not, either just by itself, or about things that are.

THEAETETUS: Apparently not.

SOCRATES: Then forming false opinions is different from thinking what is not.

THEAETETUS: Yes, they seem to be different.

SOCRATES: So we have not found false opinion within ourselves based on this approach or the pre-

vious one.

THEAETETUS: No, we have not.

SOCRATES: Then, does so-called false opinion arise in the following way?

THEAETETUS: How?

SOCRATES: We say that false opinion is a confusion of thought whereby someone says that one of

the things that are is actually another of the things that are, having mixed them up in his

mind. For in this way, though he always thinks what is, he thinks that one thing is another,

falls into error in the investigation, and may properly be said to form a false opinion.

THEAETETUS: What you have just said sounds perfect to me. For whenever someone thinks beautiful

to be ugly, or conversely, ugly to be beautiful, then he truly is forming false opinions.

SOCRATES: Theaetetus, you obviously hold me in contempt rather than awe.

THEAETETUS: What exactly do you mean?

SOCRATES: I suppose you think I shall not pick you up on this ‘truly false’, and ask about the ‘slowly

fast’ or the ‘heavily light’ or some other opposite, and whether it is possible for something

to behave oppositely to itself, and not according to its own nature, but according to the

nature of its opposite. Yet I shall let that go so that your spiritedness will not be in vain.

However, you are satisfied, you say, that forming false opinions is a confusion of thought.

THEAETETUS: I am.

SOCRATES: So according to your opinion, it is possible for the mind to posit that something is dif-

ferent from what it is.

THEAETETUS: Yes, indeed.

SOCRATES: Now, whenever the mind does this, mustn’t it actually be thinking of both things, or

one or other of them?

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192 | THEAETETUS – 189a–189e

THEAETETUS: Yes it must, either both together, or in succession.

SOCRATES: Excellent! But do you call thinking what I call thinking?

THEAETETUS: What do you call thinking?

SOCRATES: Speech that the soul itself carries on with itself about the matters it is considering. I am

demonstrating my ignorance here, yet it seems to me that when the soul is engaging in

thought, it is really engaging in discourse, asking questions to itself and answering them,

and making assertions or denials. But when it has come to a determination, whether slowly

or through sudden realisation, and it unwaveringly asserts the same thing, that we designate

as its opinion. So then, I, for my part, refer to thinking as speaking, and opinion as speech,

not spoken to another person or voiced, but delivered in silence to oneself. What do you say?

THEAETETUS: I agree.

SOCRATES: So whenever someone thinks of one thing as another, he also seems to be telling himself

that one thing is the other.

THEAETETUS: Indeed.

SOCRATES: Now, try to recall if you have ever said to yourself that beauty is most assuredly ugly,

or that injustice is just. In short, consider whether you ever tried to persuade yourself that

one thing is in fact another. No, on the contrary, you have never dared, even in your sleep,

to say to yourself that odd is even, or anything of that sort.

THEAETETUS: What you say is true.

SOCRATES: And do you think that anyone else, sane or insane, ever seriously tried to tell himself,

with any conviction, that an ox must be a horse or that two must be one?

THEAETETUS: By Zeus, I don’t think so.

SOCRATES: Now, if speaking to yourself is thinking, no one who speaks and thinks of two things

and is apprehending both with the soul, would say or think that one is the other. And you

must allow me to use that expression, for what I mean is that nobody thinks that ugliness

is beautiful, or anything else of that sort.

THEAETETUS: Yes, Socrates, I shall allow it and I agree with what you say.

SOCRATES: So when thinking of both, it is impossible to think that one is the other.

THEAETETUS: So it seems.

SOCRATES: However, thinking about only one, and not thinking of the other at all, he would never

think that one is the other.

THEAETETUS: What you say is true, for in that case he would also have to be apprehending the one

he is not thinking about.

SOCRATES: So confusion of thought is not possible, either through thinking of both of them, or of

one of them. So then, anyone who defines false opinion as thinking that one thing is another

would be talking nonsense, for there is evidently no false opinion in us, either on this basis

or on the basis of our previous discussions.

THEAETETUS: It seems not.

SOCRATES: However, Theaetetus, if we cannot show that there is false opinion, we shall be forced

to admit a number of absurdities.

THEAETETUS: What sort of absurdities?

SOCRATES: I shall not tell you until I have tried to explore this in every way possible. Indeed, I

would be ashamed on our behalf if in our present difficulty we were forced to agree with

anything I am saying. However, if we find what we are seeking, and become free, then we

shall discuss this as something that happens to others while we stand aloof from the ridicule.

But if we become utterly perplexed and humbled, I think we shall surrender to the argument

and let it walk on us and do with us as it will, as though we had come down with an illness.

Now listen, I find there is still one way of enquiry open to us.

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THEAETETUS: Just tell me.

SOCRATES: I say that we were wrong when we agreed that it is impossible for someone to be

deceived and think that the things that he knows are things he does not know, for in a way

this is possible.

THEAETETUS: You are expressing what I suspected at the time, when we said that such a thing could

happen. Is it that I, who know Socrates, see someone else at a distance whom I do not know

and believe that person to be Socrates, whom I do know? For what you describe could hap-

pen in that way.

SOCRATES: Didn’t we reject that idea, because it made out that we do not know the things we know

when we have known them?

THEAETETUS: Yes, certainly.

SOCRATES: Well, let us not propose that but the following, which may be somewhat acceptable to

us or may challenge us. But really, we are in such a state that we must thoroughly test every

turn of an argument. Consider whether this makes sense. Is it possible to learn something

that you did not know previously?

THEAETETUS: It is, indeed.

SOCRATES: And then something else, and so on?

THEAETETUS: Why not?

SOCRATES: Now assume, for the sake of the argument, that there is a block of wax in our souls,

larger in some, smaller in others, some made of purer wax, others of more impure wax,

some harder, others softer, while there are others with the proper balance.

THEAETETUS: I am assuming this.

SOCRATES: Let us declare that this is indeed a gift from Memory, the mother of the Muses, and that

whatever we may wish to remember of what we see, or hear, or think up for ourselves, is

stamped on the wax, like impressions on wax seals, by holding the wax under the percep-

tions or concepts. Whatever is imprinted is remembered and known for as long as its image

may endure, while anything that is erased or that cannot get imprinted is forgotten and not

known.

THEAETETUS: Let’s accept that.

SOCRATES: Well, consider whether someone who has knowledge of things, and is considering some-

thing he has seen or heard, could form a false opinion in such a manner.

THEAETETUS: In what manner?

SOCRATES: By believing that things that he knows are, at one time, things that he knows, and at

another, things he does not know, occurrences that we improperly agreed to be impossible

in our previous discussion.

THEAETETUS: And what do you say now?

SOCRATES: We must begin discussing the issues again, making the following distinctions. It is

impossible for a person to believe that something he knows and has in memory in the soul,

and that he is not perceiving, is another thing he knows and whose wax stamp he also pos-

sesses, though he is not perceiving it. Nor again, can he believe that what he knows is some-

thing he does not know, and whose wax impression he does not possess. Nor could he think

that something he doesn’t know is another thing he does not know, nor something he does

know. Neither could he imagine that something he is actually perceiving is another thing

he is perceiving, nor that something he is perceiving is something he is not perceiving. Nor

that something he is not perceiving is something else he is not perceiving, nor something

he actually is perceiving.

And furthermore, to believe that something he knows and is perceiving, and whose

wax impression accords with his perception, is in fact another thing he knows and perceives,

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194 | THEAETETUS – 191b–192b

and whose impression accords with the perception, is even more impossible, if that is actu-

ally possible, than the other instances. And he cannot believe that what he knows and per-

ceives and remembers properly is another thing he knows, nor another thing he perceives.

Nor again, can he think that what he neither knows nor perceives is something else he nei-

ther knows nor perceives. Nor that what he neither knows nor perceives is something else

he does not know. Nor that what he neither knows nor perceives is something else he does

not perceive. All these instances compete in their inability to form any false opinion in any-

one. Indeed, it is in the remaining instances, if anywhere, that false opinion must lie.

THEAETETUS: In what instances? Perhaps I would learn more from them, for at the moment I am

not following.

SOCRATES: In cases where someone knows, but thinks the things are other things that he knows

and perceives, or that he does not know but yet perceives. Or where he thinks what he

knows and perceives are other things he knows and perceives.

THEAETETUS: Now I am even more adrift than before.

SOCRATES: Well, listen to this once more. I know Theodorus, and I remember within myself what

he is like, and the same applies to Theaetetus. At certain times I see them, and sometimes I

do not. At times I touch them, and other times not, or I hear them, or have other perceptions

of them, while at other times I have no perception of them whatsoever. But do I remember

you, nonetheless, and do I know you within myself?

THEAETETUS: Yes, certainly.

SOCRATES: Now this is the first point I wish to make clear, that someone can perceive or not per-

ceive the things he knows.

THEAETETUS: True.

SOCRATES: And in the case of things he does not know, he frequently cannot perceive them either,

but often he can merely perceive them.

THEAETETUS: This is true also.

SOCRATES: Let us see if you can follow me better now. If Socrates knows Theodorus and

Theaetetus, but sees neither of them, nor has he any other present perception of them, he

would never form an opinion within himself that Theaetetus is Theodorus. Am I making

any sense?

THEAETETUS: Yes, this is true.

SOCRATES: Now this was the first of these instances I referred to.

THEAETETUS: It was indeed.

SOCRATES: Then the second instance is that knowing one of you, not knowing the other, and per-

ceiving neither of you, I would never think that the one I know is the one I do not know.

THEAETETUS: Correct.

SOCRATES: And thirdly, neither knowing nor perceiving either of you, I would not believe that one

whom I do not know is another whom I do not know. Now, assume you have heard again

all the previous instances in which I never form a false opinion about you and Theodorus,

if I know you both, or do not know you both, or if I know one and not the other. And the

same argument applies to perceiving. Do you follow?

THEAETETUS: I follow.

SOCRATES: Then what remains is the formation of false opinion in cases where I know you and

Theodorus, and have the imprints of both of you in that wax, just like the impressions from

seals. Seeing you both from afar, but not very well, I hurry to match your particular imprint

to your particular visual appearance, by fitting it precisely onto its own trace in memory in

order to bring about recognition. But I get these wrong, and just like people who put their

shoes on the wrong feet, I swap them around and set the appearance of one against the

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imprint of the other. Or my error is like what happens to the appearance of things in mirrors

where left turns into right, and it is in these cases that varieties in opinion, and false opinion,

occur.

THEAETETUS: That is quite likely, Socrates. You are giving a wonderful account of what happens

to opinion.

SOCRATES: There is also the case where I know both of you and I am perceiving one and not the

other, but my perception of the former does not accord with my knowledge. This is the case

I was describing earlier, when you did not understand me.

THEAETETUS: No, I did not.

SOCRATES: Well, I was saying that if you know someone and perceive them and your knowledge

of them accords with your perception, you will never think they are someone else whom

you know and perceive, the knowledge of whom also, in turn, accords with your perception.

Was that the point?

THEAETETUS: Yes.

SOCRATES: What remains, I presume, is the current formulation in which we say that false opinion

arises for someone who knows both of you, and sees or has some other perception of both

without having the wax imprints in accord with his perception of them. And so he shoots

wide of the target like a poor archer and misses the mark, and we have come to refer to this

as falsehood.

THEAETETUS: And properly so.

SOCRATES: And whenever there is present perception corresponding to one of the imprints, but not

to another, and the one whose perception is absent is matched with the present perception,

in all these cases the mind is deceived.

To sum up, in cases where one does not know, and has perceived, it seems there is

no possibility of deception or false opinion if what we are saying is in any way sound. But

it is in the particular cases where we both know and perceive that opinion twists and turns

and becomes true or false, being true when it directly associates things in line with the

proper impressions and imprints, but false when it goes crosswise to the wrong ones.

THEAETETUS: Isn’t that beautifully described, Socrates?

SOCRATES: When you have heard what is coming next you will say so all the more. Indeed, forming

opinions is beautiful when they are true, but shameful when they are false.

THEAETETUS: This must be so.

SOCRATES: Now they say that these differences arise in the following way. When the wax in a per-

son’s soul is deep and plentiful, smooth and evenly wrought, and the perceptions that come

in through the senses are impressed upon this waxen heart of the soul, as Homer poetically

calls its resemblance to wax,

then the impressions generated by the perceptions are clear,

and as they have sufficient depth, they are enduring. And such people learn easily and then

remember, since they do not confuse the imprints from the perceptions, but form opinions

that are true. As the imprints are also clear and have abundant space, they quickly assign

them to their own individual impressions, that are called things that are, and these people

are called wise. Don’t you agree?

THEAETETUS: I couldn’t agree more.

SOCRATES: But when a person’s heart is rugged, a condition praised by the all-wise poet, or

when it is sullied or made from impure wax, or is extremely soft or hard, those with soft

wax learn readily but are prone to forgetfulness, while the opposite applies to those with

hard wax.

Those who have rugged and coarse hearts, somewhat stony with plentiful admixture

of earth and filth, retain unclear impressions. And anyone whose wax is hard also retains

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196 | THEAETETUS – 193d–194e

unclear impressions, as there is no depth in them, while if their wax is soft the impressions

quickly become indistinct as they melt into one another. And if, besides all this, they are

jumbled together due to the confined space in someone’s tiny little soul, they are even more

unclear. All these people are inclined to form false opinions, for whenever they see or hear

or think of anything, they are unable to assign it quickly to its proper imprint. Instead, they

are slow, and as they assign them incorrectly, they mis-see, mishear and misconceive most

things, and are said, in turn, to be ignorant and deceived about things that are.

THEAETETUS: You are describing these men very accurately, Socrates.

SOCRATES: So should we say that there are false opinions within us?

THEAETETUS: Definitely.

SOCRATES: And true opinions?

THEAETETUS: True also.

SOCRATES: Now, at this stage, do we think we have reached adequate agreement that there really

are these two kinds of opinion?

THEAETETUS: Very much so.

SOCRATES: But, Theaetetus, a talkative man is inclined to be truly formidable and disagreeable!

THEAETETUS: Why? What are you talking about?

SOCRATES: I am annoyed about my own stupidity and how truly verbose I am. Indeed, what other

word could you use for someone who drags discussions this way and that, and cannot be

convinced because he is stupid and is hard to tear away from any proposal?

THEAETETUS: Oh, but why are you annoyed?

SOCRATES: Not only am I annoyed, but I am fearful about how I would respond if someone were

to ask me, “Socrates, have you really discovered false opinion, that it lies neither in the

relation of perceptions to one another, nor in the interrelationship of thoughts, but in the

connection between perception and thought?” I think I would agree, priding myself as

though we had made a fine discovery.

THEAETETUS: Well, Socrates, I don’t think we need be ashamed of what we have just demonstrated.

SOCRATES: “In that case,” says he, “does that mean that we shall never believe that a man, whom

we only think of but do not see, is a horse, which we neither see nor touch but only think

of, though we perceive nothing else about it?” I presume I shall confirm that this is what

we mean.

THEAETETUS: And rightly so.

SOCRATES: “Well then,” he continues, “based on this account, one could never believe that the

eleven that one merely thinks of are twelve, which again one merely thinks of.” Come on,

you give the response this time.

THEAETETUS: Well, I reply that someone who is seeing them or touching them may think that the

eleven are twelve. However, he would never form that opinion about the numbers which

he holds in mind.

SOCRATES: What about this? Do you think anyone ever considered five and seven within himself,

and I do not mean that he has five men and seven men in front of him or anything like that; I

mean just five and seven themselves, which we say have memorial imprints in the wax, and

cannot be the subject of false opinion? Now, if someone considered these numbers themselves,

talking to himself and asking how much precisely they are, would one person say and think

it is eleven, while another says twelve, or would everyone say and think that it is twelve?

THEAETETUS: No, by Zeus, there are obviously many who would say eleven, and in the case of

larger numbers there are more errors, for I presume you are talking about all numbers.

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THEAETETUS – 195a–196b | 197

–––––

Iliad ii.851, xvi.554. The Homeric word for heart is kear or ker, which superficially resembles the word for wax, kēros.

Theaetetus, David Horan translation, 6 Nov 25

SOCRATES: Yes, your presumption is correct. Now consider what is happening in this instance, and

whether twelve itself, imprinted on the wax, is thought to be eleven.

THEAETETUS: So it seems.

SOCRATES: Hasn’t our discussion arrived back at the initial proposals? For anyone involved in this

error believes that something he knows is another thing that he also knows, and we said

that this is impossible. Indeed, this was the very point which forced us to deny that there

can be false opinion, lest the same person be constrained to know and not know the same

things at the same time.

THEAETETUS: Very true.

SOCRATES: In that case, we must explain the formation of false opinion in some other way than by

the misalignment of thought relative to perception. For if it was this, we would never be

deceived in the internal thoughts themselves. But now, either there is actually no false opin-

ion or it is possible for a person not to know the things which he knows. Which of these

options would you choose?

THEAETETUS: You are presenting an impossible choice, Socrates.

SOCRATES: And yet the argument is not going to permit both of them. Nonetheless, should we risk

everything and try something audacious?

THEAETETUS: How?

SOCRATES: Let us decide to state what knowing is actually like.

THEAETETUS: What is so audacious about that?

SOCRATES: You seem not to appreciate that our entire discourse from the beginning has been a

search for knowledge on the basis that we do not know what it actually is.

THEAETETUS: I do appreciate this.

SOCRATES: Then does it not seem audacious to be elucidating what knowing is like without knowing

what knowledge is? But in fact, Theaetetus, we have been infected for some time by impure

discourse. For we have repeatedly said ‘we realise’ and ‘we do not realise’, ‘we know’ and

‘we do not know’, as if we understood one another, though we still did not know about

knowledge. Even now, if you don’t mind, at this very moment we resorted again to ‘not

knowing’ and ‘understanding’, as if it were appropriate for us to use them, when we are

actually deprived of knowledge.

THEAETETUS: But how could you conduct discourse at all, Socrates, if you avoided these phrases?

SOCRATES: Well, I couldn’t, being the man I am, unless I was an argumentative fellow, the sort of

man who, if he were here now, would tell us to avoid these phrases and would rebuke us

fiercely for the deficiencies I am referring to. But since we are ordinary folk, would you

like me to venture a statement on what knowing is like? It appears to me that this might be

of some assistance.

THEAETETUS: Venture away, by Zeus, and you will be generously forgiven if you do not avoid these

phrases.

SOCRATES: Well, have you heard what they declare that knowing is these days?

THEAETETUS: I probably have but I cannot recall just now.

SOCRATES: I believe they say that it is ‘having knowledge’.

THEAETETUS: True.

SOCRATES: Now, we shall change it slightly and say ‘the acquisition of knowledge’.

THEAETETUS: But how can you say that this is different from the other wording?

SOCRATES: Perhaps it is not, but when you have heard what I think, then we shall examine it

together.

THEAETETUS: Yes, if I am actually able to.

SOCRATES: Well, having does not appear to me to be the same as acquiring. For example, if someone

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198 | THEAETETUS – 196c–197b

buys a cloak and it is at his disposal but he does not wear it, we would say that he has

acquired it but does not have it.

THEAETETUS: Quite right.

SOCRATES: Look now, is it also possible on this basis to acquire knowledge and not have it, just as

if someone had captured wild birds, pigeons or the like, and provided an aviary at his home

and reared them, we would probably say that in a certain sense he always has them because

he has acquired them. Is this so?

THEAETETUS: Yes.

SOCRATES: And yet in another sense he does not have any of them but he has gained power over

them, since he has made them available in an enclosure at home to catch and hold whenever

he wishes, capturing the one he wants and releasing it again, and being able to do this as

often as he wants.

THEAETETUS: This is so.

SOCRATES: Again, just as we provided the souls with some undefined lump of wax in our previous

discussion, we are now building an aviary for a great variety of birds in each soul. Some of

these are arranged in flocks and they keep apart from the rest, others form smaller groups,

while some birds are solitary and fly as they will among all their fellows.

THEAETETUS: Let the aviary be built. What happens next?

SOCRATES: Well, we should say that while we are infants this structure is empty, and we should

appreciate that the birds are things which are known. A person who has acquired knowledge

confines it in the enclosure, and we say that he has learned or discovered the matter of

which this is the knowledge, and that is what knowing is.

THEAETETUS: So be it.

SOCRATES: Now, consider the process by which we recapture this knowledge whenever we wish,

retain it, and then let it go again. Consider whether these deserve the same name as the

initial acquisition, or a different name. You may understand my meaning more clearly from

this example. Is there a subject you call arithmetic?

THEAETETUS: Yes.

SOCRATES: Now, assume that this is a hunt for items of knowledge about all odd or even numbers.

THEAETETUS: I am assuming this.

SOCRATES: And I presume that, by means of this subject, a man has items of knowledge about

number at his disposal, and also transmits them to someone else.

THEAETETUS: Yes.

SOCRATES: And we refer to transmitting as teaching, apprehending as learning, and having an acqui-

sition within that aviary as knowing.

THEAETETUS: Yes, certainly.

SOCRATES: Now pay attention to the following. Will the arithmetician who is perfect have knowl-

edge of all number and nothing less, since he has the details of the knowledge of all numbers

in his soul?

THEAETETUS: Of course.

SOCRATES: Well, would a man like this, in mind, ever enumerate anything, either the numbers

themselves, or external objects which have number?

THEAETETUS: Of course.

SOCRATES: And we shall propose that enumeration is the process of finding out what the relevant

number actually is.

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THEAETETUS – 197c–198c | 199

–––––

The Greek verb for ‘I have’ can mean not only ‘I possess’, but also ‘I have hold of it’ or ‘I have it on’, e.g. in the case

of an article of clothing.

Theaetetus, David Horan translation, 6 Nov 25

THEAETETUS: It is.

SOCRATES: So we have agreed that this man knows all number, and yet he is trying to find out what

he knows, as if he did not know it. Indeed, I presume you are aware of such contradictory

statements.

THEAETETUS: Yes, I am.

SOCRATES: Now, when we compared this to the acquisition and hunting of pigeons, we said that

the hunt had two aspects. The first is prior to the acquisition for the sake of acquiring some-

thing, and then, once acquired, there is capturing and having to hand whatever had previ-

ously been acquired. And in this way too, it is possible for a man to learn the same things

again, things of which he had previous knowledge, having learned them and known them.

Can’t he take up the knowledge of each of them again and retain it, knowledge which he

does not have immediately in mind?

THEAETETUS: True.

SOCRATES: This is what I was asking earlier. What terms should be used to describe the arithmeti-

cian who sets about calculating, or the grammarian who goes to read something? In such

cases, is a person who knows, going to learn again for himself that which he already knows?

THEAETETUS: That would be strange, Socrates.

SOCRATES: But should we say that he is going to read or compute things which he does not know,

when we have conceded that he knows all letters and all numbers?

THEAETETUS: No, that too is unreasonable.

SOCRATES: Well, would you like us to say that we do not care about names, and that someone can

drag knowing and learning wherever they please? But since we have defined the acquisition

of knowledge as one thing, and having it as another, it is impossible for someone not to

have acquired that which he has acquired, and consequently it never happens that someone

does not know that which he knows. However, we do say that it is possible to pick up a

false opinion about it, for it is possible not to hold the knowledge of that, but another knowl-

edge instead. This happens when someone is on the hunt for an item of knowledge which

is flying about the aviary, but mistakenly grabs a different one instead of the one he wanted.

So, in the case where he thought that the eleven was twelve, he had caught within himself

the knowledge of the eleven rather than the twelve, like catching a dove instead of a pigeon.

THEAETETUS: Yes, that makes sense.

SOCRATES: But, whenever he catches what he is trying to catch, he is unerring and he thinks things

that are. And so in this way there can be both true and false opinion, and the issues which

troubled us earlier no longer present an obstacle. Perhaps you will agree with me, or will

you take a different approach?

THEAETETUS: I take this approach.

SOCRATES: Well then, we are rid of the issue of people not knowing things that they know, for it

can never turn out that we have not acquired the things we have acquired, whether we are

deceived about something or not. But it seems to me that another more formidable issue is

looming.

THEAETETUS: What sort of issue?

SOCRATES: Whether the interchange of pieces of knowledge will ever give rise to false opinion.

THEAETETUS: How so?

SOCRATES: The first concern is that someone who has knowledge of something is ignorant of that

very thing, not on account of ignorance, but on account of his own knowledge. Then

comes the statement that he thinks that this thing is something different, and the different

thing is this thing. Is it not very unreasonable that when knowledge is present, the soul

knows nothing and is utterly ignorant? For based on this account, why couldn’t the presence

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200 | THEAETETUS – 198d–199d

of ignorance enable us to know something, or blindness make us see, if knowledge ever

really does make someone ignorant?

THEAETETUS: Well, Socrates, perhaps we went wrong when we proposed that these birds stand

only for items of knowledge, and we should also propose that there are ignorances flying

around in the soul at the same time, and the seeker sometimes gets hold of knowledge and

sometimes of ignorance concerning the same thing. He then forms false opinions on account

of the ignorance, and true opinions on account of the knowledge.

SOCRATES: I can hardly refrain from praising you, Theaetetus. However, you should examine what

you have said once more. Now, let it be as you say, that someone who gets hold of ignorance

will form false opinions, according to you. Is that so?

THEAETETUS: Yes.

SOCRATES: Of course he will not think that he is forming false opinions.

THEAETETUS: How could he?

SOCRATES: Indeed, he will think they are actually true, and he will adopt the stance of a man who

knows on matters where he is in error.

THEAETETUS: Yes, he will.

SOCRATES: So he will believe he is in possession of knowledge, not ignorance, because that is what

he has hunted down.

THEAETETUS: Obviously.

SOCRATES: Well, we are back again at our initial difficulty after a very circuitous diversion. Indeed,

that disputatious man will laugh and say, “How does this work, my good fellows? Does

someone who knows both believe that some item of knowledge which he knows is some

ignorance which he also knows? Or does he know neither of them, and think that one which

he does not know is another which he does not know? Or having known one and not the

other, does he believe that the one he knows is the one he does not know, or that the one he

does not know is the one he does know? Or again, will you go on to say to me that there

are additional knowledges about the items of knowledge and the ignorances, and that he

acquires these knowledges and keeps them in some other ridiculous aviaries or in wax

imprints? Does he know these as long as he possesses them, though he may not have them

immediately at his disposal, in his soul? Well, are you going to be compelled to go through

this same cycle indefinitely without getting anywhere?” How shall we respond to these

questions, Theaetetus?

THEAETETUS: By Zeus, Socrates, I don’t know what we should say.

SOCRATES: So in that case, my boy, was the argument right to rebuke us and show that we were

wrong to set knowledge aside and seek false opinion first, something which it is impossible

to understand until we have a proper grasp of what knowledge actually is?

THEAETETUS: As things stand, Socrates, we must believe what you are saying.

SOCRATES: So what are we to say that knowledge is? For I presume we are not going to give up yet.

THEAETETUS: Far from it, unless you yourself have had enough.

SOCRATES: Tell me then, what definite statement can we make that involves us in the least self-

contradiction?

THEAETETUS: The very proposition we tried before. In fact, it is the only one I have.

SOCRATES: What is it?

THEAETETUS: That knowledge is true opinion. Forming true opinions is, after all, a process which

is supposedly free from error, and whatever arises on this basis is entirely noble and good.

SOCRATES: The guide by the river bank says, “You will be shown the depth, Theaetetus”, and in

this case, once we proceed with our search, perhaps something which turns up along the

way may reveal what we are seeking, but if we wait, nothing will become clear.

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THEAETETUS – 199e–201a | 201

Theaetetus, David Horan translation, 6 Nov 25

THEAETETUS: You’re right, so let’s go ahead and consider this.

SOCRATES: Well, this will be a brief investigation, for there is a whole profession pointing out to

you that true opinion is not knowledge.

THEAETETUS: How is that? What profession?

SOCRATES: The profession of the wisest men of all, whom we call orators and advocates. For these

men use their skill to persuade rather than teach, and they make people form the opinions

they want them to form. Or do you believe that there are teachers so clever that they can

adequately teach the truth about what happened to people whose money was stolen or who

were otherwise assaulted to people who were not present? Can they do this in the little time

allowed by the water-clock in the court?

THEAETETUS: I don’t believe that they can teach them at all, but they may persuade them.

SOCRATES: And don’t you say that persuading them is making them form an opinion?

THEAETETUS: Of course.

SOCRATES: Now, when a jury is justly persuaded about matters that only an eyewitness and no one

else could know, on that occasion they are judging from hearsay. They have caught hold of

a true opinion, but haven’t they judged without knowledge, having been persuaded of what

is right, if their adjudication is actually sound?

THEAETETUS: Entirely so.

SOCRATES: But, my friend, if knowledge and true opinion are really the same, the best of jurors

could never form a correct opinion in the absence of knowledge. So in that case, it seems

they are different from one another.

THEAETETUS: Oh, Socrates, I had forgotten something that I once heard someone saying, but I

remember now. He said that true opinion along with an account is knowledge, while in the

absence of an account it is outside the realm of knowledge. And whatever is without an

account is not knowable – yes, that’s the very term he used – while anything that has an

account is knowable.

SOCRATES: Well said, but now explain how he distinguished the knowable things from the unknow-

able, for I may have heard the same things you have heard.

THEAETETUS: Well, I don’t know if I can work that out. However, if someone else were to explain

it, I think that I could follow.

SOCRATES: Then listen to a dream in return for a dream, for I too imagined that I heard from some

people that the primary so-called elements from which we and all else are compounded

lack any account. For since each, just by itself, may only be named, and nothing else can

be said of it, either that it is or that it is not, for in that case we would be assigning being or

non-being to it, but we must apply nothing if we are to speak of itself alone. So we should

not apply ‘it’ or ‘that’ or ‘each’ or ‘only’ or ‘this’ or the numerous other terms like them, for

these are in circulation and are applied generally, being different from whatever they are

assigned to. But if it were possible to describe an element and it had its own particular

account, it would have to be described without all of the others. But as things stand, it is

impossible for any of the primals to be expressed in an account, for they can only be named,

since name is all they have. But when things are compounded from the primals, their names

are woven together just as they themselves are woven, and they generate an account, for

the essence of an account is an interweaving of names. Thus, the elements have no account

and are unknowable, and yet they are perceivable, while the compounds are knowable and

describable and can be the object of true opinion. Now, whenever someone has acquired a

true opinion of something, without an account, then his soul has arrived at the truth about

it, but does not know it, for a man who can neither give nor receive an account of a thing

is ignorant about it. But once he has acquired an account, all these other things can happen,

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202 | THEAETETUS – 201b–202c

and he is perfected in knowledge. Was your dream like that or was it different?

THEAETETUS: It was exactly like that.

SOCRATES: Are you satisfied then, and are you proposing that true opinion with an account is

knowledge?

THEAETETUS: Quite so.

SOCRATES: Well, Theaetetus, have we really captured something this very day that generations of

wise men have sought and grown old without finding?

THEAETETUS: Socrates, I really believe that what we have just said is an excellent description.

SOCRATES: And that is quite likely so, for what knowledge could there be in the absence of an

account and true opinion? However, there is one thing we said which is bothering me.

THEAETETUS: What is it?

SOCRATES: What seems like the cleverest statement of all: that the elements are unknowable, while

the class of compounds is knowable.

THEAETETUS: What’s wrong with that?

SOCRATES: Well, we need to know, for we are holding the patterns of the argument like hostages,

patterns used by the very person who said all this.

THEAETETUS: What patterns?

SOCRATES: The elements and syllables of writing, or do you imagine that the person who said all

we are recounting had something else in view?

THEAETETUS: No, only these.

SOCRATES: Now let us test them, and let us test ourselves in particular, as to whether we learned

writing on this basis or not. Well, in the first place, do the syllables have an account while

the letters do not?

THEAETETUS: Perhaps.

SOCRATES: That is certainly how it seems to me. If someone were to ask about the first syllable of

‘Socrates’, and said “Theaetetus, what is SO?”, how would you respond?

THEAETETUS: That it is S and O.

SOCRATES: And isn’t that your account of the syllable?

THEAETETUS: It is.

SOCRATES: Very well, now give an account of S in the same way.

THEAETETUS: But how could anyone speak of the letters of a letter? Actually, Socrates, the S is

one of the voiceless letters, it is just a sound like a hissing of the tongue, while B, for its

part, has neither voice nor sound, nor have most of the letters. So it is quite appropriate to

say they have no account, when even the clearest of them, the seven vowels, have a voice

alone, but no account at all.

SOCRATES: So, my friend, we have come to this conclusion about knowledge.

THEAETETUS: It appears that we have.

SOCRATES: But what about this? Have we really shown that the elements are unknowable, though

the syllables are knowable?

THEAETETUS: Quite likely.

SOCRATES: Well then, are we saying that the syllable is both letters, or all of them if there are more

than two, or is it a single form which arises from putting them together?

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THEAETETUS – 202d–203c | 203

–––––

The Greek word for element and letter is the same. The initial reference here is to a response based upon syllables

rather than letters or elements.

Theaetetus actually says, “That it’s sigma and omega”, using the names of the first two Greek letters in Socrates’ name.

The ‘seven’ are the seven vowels of ancient Greek, as contrasted with two classes of consonant – mutes like B, which

cannot be pronounced without a vowel, and semi-vowels like S, which can.

Theaetetus, David Horan translation, 6 Nov 25

THEAETETUS: I presume we are referring to all of them.

SOCRATES: Then consider two, the S and the O. This pair is the first syllable of my name. Can

someone who knows the syllable avoid knowing both letters?

THEAETETUS: Of course not.

SOCRATES: So he knows the S and the O.

THEAETETUS: Yes.

SOCRATES: Yes, but does he know both without knowing one or the other?

THEAETETUS: No, that would be bizarre and illogical, Socrates.

SOCRATES: However, if it really is necessary for someone to know each letter if he is to know both,

then anyone who is ever going to know the syllable absolutely must have prior knowledge

of the letters. On this basis, our nice proposition has taken to its heels and fled.

THEAETETUS: And very suddenly too!

SOCRATES: Yes, we are not being careful enough with it. Perhaps we should be proposing that the

syllable is not the letters, but a single form arising from them, having a single form of its

own that is different from the letters.

THEAETETUS: Yes, indeed, and that is probably a better suggestion than the other one.

SOCRATES: We should consider this, and not give up like cowards on a significant and serious

proposition.

THEAETETUS: We should not.

SOCRATES: Then let our present statement stand, that a syllable is a single form which arises from

joining the individual elements together, such as occurs in writing and in all other situations.

THEAETETUS: Yes, certainly.

SOCRATES: Therefore, it must not have parts.

THEAETETUS: Why is that?

SOCRATES: Because the whole must be all the parts of anything which has parts, or do you also say

that the whole is a single form that arises from the parts, and is different from all the parts?

THEAETETUS: I do.

SOCRATES: But do you refer to the entire and the whole as different from one another, or the

same?

THEAETETUS: I am not clear about that, but because you are asking me to respond readily, I’ll take

a chance and say that they are different.

SOCRATES: Well, Theaetetus, you have the readiness right, but we should consider whether the

answer is right.

THEAETETUS: Yes, we must do that.

SOCRATES: So wouldn’t the whole be different from the entire, according to the current argument?

THEAETETUS: Yes.

SOCRATES: What about this? Is there any difference between ‘the entire’ and ‘them all’? For

instance, when we say one, two, three, four, five, six, or twice three, or thrice two, or four

plus two, or three plus two plus one, are we talking about the same thing or something dif-

ferent in all such cases?

THEAETETUS: The same.

SOCRATES: And is that different from six?

THEAETETUS: No.

SOCRATES: Then, with each statement haven’t we referred to all six?

THEAETETUS: Yes.

SOCRATES: But if we say ‘the entire’, aren’t we referring again to one thing?

THEAETETUS: We must be.

SOCRATES: And is that a different thing from the six?

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204 | THEAETETUS – 203d–204c

THEAETETUS: No.

SOCRATES: So, in any cases involving number, do we refer to ‘the entire’ and ‘them all’ as the same?

THEAETETUS: It appears so.

SOCRATES: Then let us talk about them as follows: the number of a mile and a mile are the same,

aren’t they?

THEAETETUS: Yes.

SOCRATES: This also applies to the number of a furlong.

THEAETETUS: Yes.

SOCRATES: Similarly, in the case of an army and the number of an army, and everything of that

kind, the entire number is what each of them entirely is.

THEAETETUS: Yes.

SOCRATES: But is the number of each, anything other than the parts?

THEAETETUS: Nothing other.

SOCRATES: And in so far as something has parts, it would consist of parts?

THEAETETUS: It appears so.

SOCRATES: But we did agree that all the parts are the entire, if in fact the entire number is also the

entire.

THEAETETUS: So we did.

SOCRATES: Then the whole does not consist of parts, for if it were all the parts, the whole would

be the entire.

THEAETETUS: So it seems.

SOCRATES: But is a part, as such, part of anything other than a whole?

THEAETETUS: Yes, of the entire.

SOCRATES: Well, you are putting up a brave fight, Theaetetus, but isn’t the entire actually entire

whenever there is nothing missing?

THEAETETUS: Necessarily.

SOCRATES: But won’t that same thing from which nothing is missing be a whole? And that from

which something is missing is neither whole nor entire; from the same effect, the same

cause arises in both.

THEAETETUS: It seems to me now that there is no difference between whole and entire.

SOCRATES: Were we not saying that for anything with parts, the whole and also the entire will be

all the parts?

THEAETETUS: Yes, indeed.

SOCRATES: Now, returning to my previous enquiry, if the syllable is not the letters, it must not have

the letters as parts of itself, or else it will be the same as them and be just as knowable as

they are. Is that it?

THEAETETUS: That’s it.

SOCRATES: And to prevent this from happening, didn’t we propose that it was different from the

letters?

THEAETETUS: Yes.

SOCRATES: Well then, if the letters are not parts of the syllable, can you propose other candidates

that are part of the syllable, without, however, being the letters of the syllable?

THEAETETUS: Certainly not, Socrates, for if I were to agree that it has some parts, it would be a bit

ridiculous to ignore the letters and look for other candidates.

SOCRATES: Yes, entirely so, Theaetetus, based upon the current proposition, a syllable would be a

single indivisible form.

THEAETETUS: So it seems.

SOCRATES: Now, my friend, do you remember a little while ago we accepted what we regarded as

204 d

204 e

205 a

205 b

205 c

THEAETETUS – 204d–205c | 205

Theaetetus, David Horan translation, 6 Nov 25

a sound proposal, that there is no account of the primals from which all else is compounded

because each of them, just by itself, is uncompounded, and neither the terms ‘is’ nor ‘this’

can properly be applied to them as they describe different and distinct things, and this is

the reason why a primal is indescribable and unknowable?

THEAETETUS: I remember.

SOCRATES: Well, is this the reason why it is uniform and indivisible, or is there another? Indeed, I

can discern no other.

THEAETETUS: No, it appears that there is no other.

SOCRATES: Doesn’t the compound fall into the same category as the element, if in fact it has no

parts and is one form?

THEAETETUS: Entirely so.

SOCRATES: So then, if the compound is many elements, and is a whole with the elements as its

parts, the compounds will be just as knowable and expressible as the elements, since the

many parts have turned out to be the same as the whole.

THEAETETUS: Certainly.

SOCRATES: But if, on the other hand, the compound is one and partless, the compound, like the ele-

ment, will be just as indescribable and unknowable for the same reason. The unity and indi-

visibility will make them so.

THEAETETUS: I cannot disagree with you.

SOCRATES: So we should not accept it when someone says that the compound is knowable and

expressible while the element is not.

THEAETETUS: No, indeed not, if we are persuaded by this argument.

SOCRATES: Well then, would it be better to agree with someone who says the opposite, because of

what you yourself discern in the process of learning to write?

THEAETETUS: What do I discern?

SOCRATES: In learning to write, you have achieved no more than the ability to recognise each letter,

just by itself, with your eyes and ears, so that its position in speech or writing does not con-

fuse you.

THEAETETUS: What you say is very true.

SOCRATES: And isn’t the perfectly trained lyre player able to follow each note and say what string

it came from? And wouldn’t anyone agree that these notes are the letters of music?

THEAETETUS: They would.

SOCRATES: Now, if we had to generalise to others from the letters and syllables within our own

experience, we would say that having knowledge of the elemental category is much more

critical and important in the complete apprehension of each subject than knowledge of the

compound. And if anyone says that the compound is knowable while the element is by

nature unknowable, we shall assume that he is joking, either deliberately or unwittingly.

THEAETETUS: We certainly will.

SOCRATES: Now, I think even more proofs of this may turn up, but we must not forget the current

issue because of them. We want to see what is meant by the statement that the most complete

knowledge arises from the addition of an account to true opinion.

THEAETETUS: Yes, we need to see that.

SOCRATES: Come then, what exactly are we supposed to understand by ‘an account’? For it seems

to me to mean one of three things.

THEAETETUS: What are they?

SOCRATES: The first would involve making one’s thoughts manifest in sound, using verbs and

nouns, forming the opinion into an image in the stream issuing from the mouth, just like an

image in a mirror or in water. Or don’t you think that an account is something of that sort?

205 d

205 e

206 a

206 b

206 c

206 d

206 | THEAETETUS – 205d–206d

THEAETETUS: I do. Anyway, we do say that a person who is doing this is giving an account.

SOCRATES: What is more, this can actually be done quite easily by everybody, so anyone who is

not born deaf and dumb can explain what they think about every issue. This being the case,

anyone who forms a right opinion will turn out to have that opinion with an account, and

right opinion without knowledge will never arise at all.

THEAETETUS: True.

SOCRATES: Well, we should not be too quick to accuse the person who made the statement about

knowledge, which we are now considering, of talking nonsense, for perhaps he did not

mean this, but did not have the ability to give an answer in terms of the elements when

asked what anything is.

THEAETETUS: Can you give an example, Socrates?

SOCRATES: Yes, it is like Hesiod referring to “the one hundred wooden parts of a wagon”.

Now,

I could not say what they are, nor, I imagine, could you, but if we were asked what a wagon

is, we would be satisfied if we could say “wheels, an axle, body, rails and yoke”.

THEAETETUS: Yes, certainly.

SOCRATES: And yet, he might think we were ridiculous, just as if we responded based upon the

syllables when asked what your name was. Ridiculous because, although what we said was

correctly conceived and expressed, we thought we were grammarians who had a grammat-

ical account of Theaetetus’ name and were expressing it. Whereas, it is not possible to give

a knowledgeable account of anything until you can describe that by means of the elements

combined with true opinion, as I think we said before.

THEAETETUS: Yes, we said that.

SOCRATES: Now, he will accept that while we really do have true opinion about the wagon in this

way, someone who is able to describe its being by means of those one hundred parts, once

he has also attained this, has added an account to the true opinion, and becomes expert and

knowledgeable about the being of the wagon rather than merely opinionated, as he has

described the whole by means of the elements.

THEAETETUS: Don’t you think this is sound, Socrates?

SOCRATES: Tell me whether you think so, my friend, and whether you accept that a description of

anything based upon the elements is an account, while it is not an account if it is based on

compounds or larger units. Tell me so that we can consider it.

THEAETETUS: Yes, I certainly accept this.

SOCRATES: And do you regard anyone as knowledgeable about something when he thinks that the

same element is part of something at one moment, and part of something different the next,

or when he thinks one element, and then a different element, belongs to the same thing?

THEAETETUS: By Zeus, I do not.

SOCRATES: Then, are you forgetting that this is what you and the other boys did when you began

learning to read and write?

THEAETETUS: Do you mean that we first believed that one letter, then a different letter, belonged

to the same syllable, or we placed the same letter sometimes in the appropriate syllable,

and at other times in a different one?

SOCRATES: That is what I mean.

THEAETETUS: By Zeus, I certainly have not forgotten, nor do I regard people as knowledgeable

when they are at that stage.

SOCRATES: What about a situation where someone is writing ‘Theaetetus’ and writes TH and E

because he thinks he should, but when he goes on to try to write ‘Theodorus’, he writes T and

206 e

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207 c

207 d

207 e

208 a

THEAETETUS – 206e–208a | 207

–––––

Hesiod, Works and Days 456.

Theaetetus, David Horan translation, 6 Nov 25

E because he thinks he should?

Shall we say that this fellow knows the first syllable of

both your names?

THEAETETUS: No, we have already agreed that when a person is at that stage he does not yet know.

SOCRATES: And could he be in a similar predicament about the second syllable, and the third and

the fourth?

THEAETETUS: There is no reason why not.

SOCRATES: Therefore, when he has a description based on the letters, he will write ‘Theaetetus’

with right opinion, once he writes it in the proper sequence.

THEAETETUS: Obviously.

SOCRATES: Isn’t he still devoid of knowledge, though he is forming a right opinion according

to us?

THEAETETUS: Yes.

SOCRATES: Yet he has an account along with right opinion, for he was writing using an approach

by means of the elements, and we agreed that this constitutes an account.

THEAETETUS: True.

SOCRATES: So, my friend, here we have right opinion combined with an account that should not

yet be called knowledge.

THEAETETUS: I’m afraid so.

SOCRATES: Well, it seems our wealth was but a dream when we imagined we had a perfectly true

account of knowledge. But are we condemning it too soon? Perhaps an account should not

be defined like this, for there were three options available to a person who defines knowl-

edge as right opinion together with an account, and the last of the three still remains.

THEAETETUS: You are right to remind me. Yes, there is one remaining option. The first was an

image of thought expressed in speech, the one we have just discussed was the approach to

the entire based upon the elements. Now, what do you say the third option is?

SOCRATES: Exactly what most people would say it is – being able to express some indication by

which the item in question is distinguished from everything else.

THEAETETUS: Can you give me an example of an account of something?

SOCRATES: If you wish. For instance, the statement that the sun is the brightest of the heavenly

bodies moving round the earth would, I believe, be quite acceptable to you.

THEAETETUS: Yes, certainly.

SOCRATES: Now, understand why such a statement is made, and in fact we have just given the rea-

son. Once you understand the distinguishing characteristic by which something is distin-

guished from others, you will, some say, have obtained an account of it. But as long as you

apprehend some common feature, your account will relate to whatever entities have this in

common.

THEAETETUS: I understand, and I think it is appropriate to refer to this sort of thing as an account.

SOCRATES: Once someone with right opinion about any one of the things that are also grasps its

distinction from the others, he will become knowledgeable about that of which he was pre-

viously just opinionated.

THEAETETUS: So we say anyway.

SOCRATES: Well now, Theaetetus, since I have come closer to this statement, I understand it even

less. It is like those shadow drawings which only seem to make sense as long as you stand

far away from them.

THEAETETUS: What do you mean?

SOCRATES: I shall tell you if I can. I have right opinion about you, and if I also obtain an account

of you, I shall actually know you, but otherwise I shall only be forming opinions.

THEAETETUS: Yes.

208 b

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208 d

208 e

209 a

208 | THEAETETUS – 208b–209a

SOCRATES: But the account is an explanation of your distinctiveness.

THEAETETUS: So it is.

SOCRATES: Therefore, while I was only forming opinions, I had no mental grasp of anything at all

by which you are distinguished from others.

THEAETETUS: Apparently not.

SOCRATES: So, I had some common qualities in mind that you, as well as anyone else, possess.

THEAETETUS: So you must.

SOCRATES: Come, by Zeus, in that case how did I ever form an opinion about you rather than

anyone else? For I suppose I am thinking that this is Theaetetus, who is human and has

a nose, eyes and mouth, and so on for each of the organs. Will these ideas themselves

enable me to think of Theaetetus rather than Theodorus, or any out-and-out Mysian, as

the saying goes?

THEAETETUS: How could they?

SOCRATES: However, if I do not think only of people with a nose and eyes, but of those with a

snub-nose and protruding eyes, won’t I form an opinion, in that case, which applies to you

as much as to myself or anyone else like us?

THEAETETUS: Yes.

SOCRATES: In fact, Theaetetus will register no opinion within me until this snub-nosedness forms

a distinct record imprinted within me, which is different from the record of any other snub-

nosedness which I have seen. The same goes for your other characteristics, and this imprint

will act as a reminder if I meet you tomorrow, and will enable me to form a correct opinion

about you.

THEAETETUS: Very true.

SOCRATES: So, in each case, right opinion would be concerned with distinctiveness.

THEAETETUS: Apparently.

SOCRATES: In that case, what more can the account add to right opinion? For if you say it adds an

opinion by which something is distinguished from the others, then the process becomes

quite ridiculous.

THEAETETUS: How?

SOCRATES: When we have right opinion of things, by which they are distinguished from the others,

we are asked to add another right opinion of the same things, by which they will differ from

the others. So, the circuitousness of a roller, or a pestle, or anything like that, would be

nothing in comparison to this process which may properly be called the directions of a blind

man. Indeed, asking us to acquire what we already have so that we may understand the

things about which we form opinions, is really and truly a deed of darkness.

THEAETETUS: Is there another option? What else were you going to suggest a moment ago?

SOCRATES: Well, my boy, if adding an account means knowing the distinctiveness, rather than hav-

ing an opinion about it, our most perfect account of knowledge would be an oddity indeed.

For knowing presumably means acquiring knowledge, doesn’t it?

THEAETETUS: Yes.

SOCRATES: Therefore, it seems that when asked what knowledge is, this account replies that it is

right opinion along with knowledge of distinctiveness, for that is what acquisition of an

account is according to this.

209 b

209 c

209 d

209 e

210 a

THEAETETUS – 209b–210a | 209

–––––

Socrates actually says, “he thinks he should write theta and epsilon”, using the names of the Greek letters in the first

syllable of Theaetetus’ name. There are only two such letters because Greek represents the sound ‘th’ by the single

letter theta. Moreover, this sound was a plosive (as in English ‘fathead’) rather than a fricative (as in English ‘thin’),

and so easy enough to confuse with ‘te’.

Theaetetus, David Horan translation, 6 Nov 25

THEAETETUS: So it seems.

SOCRATES: And it is really quite simple-minded, when we are in search of knowledge, to say that

it is right opinion along with knowledge, be it of distinctiveness or anything at all. So,

Theaetetus, knowledge turns out to be neither perception nor true opinion, nor an account

along with true opinion.

THEAETETUS: It seems not.

SOCRATES: Well then, my friend, are we still pregnant or in labour in relation to knowledge, or

have we brought forth all there is?

THEAETETUS: Oh yes, by Zeus, because of you I have spoken more than I had within myself.

SOCRATES: Isn’t our art of midwifery saying that all these are wind-eggs and not worth rearing?

THEAETETUS: Most emphatically.

SOCRATES: Well, Theaetetus, if you attempt to conceive other thoughts in future, if you do conceive,

you will be filled with better thoughts because of our present enquiry. But should you remain

barren, you will be less oppressive to your associates, and gentler, as you will refrain, wisely,

from thinking that you know what you do not know. This is as much as my skill can accom-

plish, it can do no more, and I know nothing that is known by the great and wonderful men

of the past or the present. This midwifery has been allotted to me and my mother, by God,

she for women, and I for the young and noble and all who are good.

Now, I must go to the Royal Stoa to answer the charge which Meletus has laid against

me.

But in the morning, Theodorus, let us meet here again.

–––––

210 b

210 c

210 d

210 | THEAETETUS – 210b–210d

–––––

The Stoa Basileios (Royal Stoa) housed the office of Athens’ chief religious officer. Here Meletus made his formal

accusation of impiety against Socrates in front of the King Archon.