Theaetetus
in sleep, did you ever venture to say to yourself that odd is even, or
anything of the kind?
THEAETETUS: Never.
SOCRATES: And do you suppose that any other man, either in his senses
or out of them, ever seriously tried to persuade himself that an ox is a
horse, or that two are one?
THEAETETUS: Certainly not.
SOCRATES: But if thinking is talking to oneself, no one speaking and
thinking of two objects, and apprehending them both in his soul, will
say and think that the one is the other of them, and I must add, that
even you, lover of dispute as you are, had better let the word 'other'
alone (i.e. not insist that 'one' and 'other' are the same (Both words
in Greek are called eteron: compare Parmen.; Euthyd.)). I mean to say,
that no one thinks the noble to be base, or anything of the kind.
THEAETETUS: I will give up the word 'other,' Socrates; and I agree to
what you say.
SOCRATES: If a man has both of them in his thoughts, he cannot think
that the one of them is the other?
THEAETETUS: True.
SOCRATES: Neither, if he has one of them only in his mind and not the
other, can he think that one is the other?
THEAETETUS: True; for we should have to suppose that he apprehends that
which is not in his thoughts at all.
SOCRATES: Then no one who has either both or only one of the two objects
in his mind can think that the one is the other. And therefore, he who
maintains that false opinion is heterodoxy is talking nonsense; for
neither in this, any more than in the previous way, can false opinion
exist in us.
THEAETETUS: No.
SOCRATES: But if, Theaetetus, this is not admitted, we shall be driven
into many absurdities.
THEAETETUS: What are they?
SOCRATES: I will not tell you until I have endeavoured to consider the
matter from every point of view. For I should be ashamed of us if we
were driven in our perplexity to admit the absurd consequences of which
I speak. But if we find the solution, and get away from them, we may
regard them only as the difficulties of others, and the ridicule will
not attach to us. On the other hand, if we utterly fail, I suppose that
we must be humble, and allow the argument to trample us under foot,
as the sea-sick passenger is trampled upon by the sailor, and to do
anything to us. Listen, then, while I tell you how I hope to find a way
out of our difficulty.
THEAETETUS: Let me hear.
SOCRATES: I think that we were wrong in denying that a man could think
what he knew to be what he did not know; and that there is a way in
which such a deception is possible.
THEAETETUS: You mean to say, as I suspected at the time, that I may know
Socrates, and at a distance see some one who is unknown to me, and whom
I mistake for him--then the deception will occur?
SOCRATES: But has not that position been relinquished by us, because
involving the absurdity that we should know and not know the things
which we know?
THEAETETUS: True.
SOCRATES: Let us make the assertion in another form, which may or may
not have a favourable issue; but as we are in a great strait, every
argument should be turned over and tested. Tell me, then, whether I am
right in saying that you may learn a thing which at one time you did not
know?
THEAETETUS: Certainly you may.
SOCRATES: And another and another?
THEAETETUS: Yes.
SOCRATES: I would have you imagine, then, that there exists in the mind
of man a block of wax, which is of different sizes in different men;
harder, moister, and having more or less of purity in one than another,
and in some of an intermediate quality.
THEAETETUS: I see.
SOCRATES: Let us say that this tablet is a gift of Memory, the mother
of the Muses; and that when we wish to remember anything which we have
seen, or heard, or thought in our own minds, we hold the wax to the
perceptions and thoughts, and in that material receive the impression of
them as from the seal of a ring; and that we remember and know what is
imprinted as long as the image lasts; but when the image is effaced, or
cannot be taken, then we forget and do not know.
THEAETETUS: Very good.
SOCRATES: Now, when a person has this knowledge, and is considering
something which he sees or hears, may not false opinion arise in the
following manner?
THEAETETUS: In what manner?
SOCRATES: When he thinks what he knows, sometimes to be what he knows,
and sometimes to be what he does not know. We were wrong before in
denying the possibility of this.
THEAETETUS: And how would you amend the former statement?
SOCRATES: I should begin by making a list of the impossible cases which
must be excluded. (1) No one can think one thing to be another when he
does not perceive either of them, but has the memorial or seal of both
of them in his mind; nor can any mistaking of one thing for another
occur, when he only knows one, and does not know, and has no impression
of the other; nor can he think that one thing which he does not know is
another thing which he does not know, or that what he does not know
is what he knows; nor (2) that one thing which he perceives is another
thing which he perceives, or that something which he perceives is
something which he does not perceive; or that something which he does
not perceive is something else which he does not perceive; or that
something which he does not perceive is something which he perceives;
nor again (3) can he think that something which he knows and perceives,
and of which he has the impression coinciding with sense, is something
else which he knows and perceives, and of which he has the impression
coinciding with sense;--this last case, if possible, is still more
inconceivable than the others; nor (4) can he think that something which
he knows and perceives, and of which he has the memorial coinciding with
sense, is something else which he knows; nor so long as these agree,
can he think that a thing which he knows and perceives is another thing
which he perceives; or that a thing which he does not know and does not
perceive, is the same as another thing which he does not know and does
not perceive;--nor again, can he suppose that a thing which he does not
know and does not perceive is the same as another thing which he does
not know; or that a thing which he does not know and does not perceive
is another thing which he does not perceive:--All these utterly and
absolutely exclude the possibility of false opinion. The only cases, if
any, which remain, are the following.
THEAETETUS: What are they? If you tell me, I may perhaps understand you
better; but at present I am unable to follow you.
SOCRATES: A person may think that some things which he knows, or which
he perceives and does not know, are some other things which he knows and
perceives; or that some things which he knows and perceives, are other
things which he knows and perceives.
THEAETETUS: I understand you less than ever now.
SOCRATES: Hear me once more, then:--I, knowing Theodorus, and
remembering in my own mind what sort of person he is, and also what sort
of person Theaetetus is, at one time see them, and at another time do
not see them, and sometimes I touch them, and at another time not, or
at one time I may hear them or perceive them in some other way, and at
another time not perceive them, but still I remember them, and know them
in my own mind.
THEAETETUS: Very true.
SOCRATES: Then, first of all, I want you to understand that a man may or
may not perceive sensibly that which he knows.
THEAETETUS: True.
SOCRATES: And that which he does not know will sometimes not be
perceived by him and sometimes will be perceived and only perceived?
THEAETETUS: That is also true.
SOCRATES: See whether you can follow me better now: Socrates can
recognize Theodorus and Theaetetus, but he sees neither of them,
nor does he perceive them in any other way; he cannot then by any
possibility imagine in his own mind that Theaetetus is Theodorus. Am I
not right?
THEAETETUS: You are quite right.
SOCRATES: Then that was the first case of which I spoke.
THEAETETUS: Yes.
SOCRATES: The second case was, that I, knowing one of you and not
knowing the other, and perceiving neither, can never think him whom I
know to be him whom I do not know.
THEAETETUS: True.
SOCRATES: In the third case, not knowing and not perceiving either of
you, I cannot think that one of you whom I do not know is the other whom
I do not know. I need not again go over the catalogue of excluded cases,
in which I cannot form a false opinion about you and Theodorus, either
when I know both or when I am in ignorance of both, or when I know one
and not the other. And the same of perceiving: do you understand me?
THEAETETUS: I do.
SOCRATES: The only possibility of erroneous opinion is, when knowing you
and Theodorus, and having on the waxen block the impression of both of
you given as by a seal, but seeing you imperfectly and at a distance,
I try to assign the right impression of memory to the right visual
impression, and to fit this into its own print: if I succeed,
recognition will take place; but if I fail and transpose them, putting
the foot into the wrong shoe--that is to say, putting the vision of
either of you on to the wrong impression, or if my mind, like the sight
in a mirror, which is transferred from right to left, err by reason of
some similar affection, then 'heterodoxy' and false opinion ensues.
THEAETETUS: Yes, Socrates, you have described the nature of opinion with
wonderful exactness.
SOCRATES: Or again, when I know both of you, and perceive as well as
know one of you, but not the other, and my knowledge of him does not
accord with perception--that was the case put by me just now which you
did not understand.
THEAETETUS: No, I did not.
SOCRATES: I meant to say, that when a person knows and perceives one of
you, his knowledge coincides with his perception, he will never think
him to be some other person, whom he knows and perceives, and the
knowledge of whom coincides with his perception--for that also was a
case supposed.
THEAETETUS: True.
SOCRATES: But there was an omission of the further case, in which, as
we now say, false opinion may arise, when knowing both, and seeing, or
having some other sensible perception of both, I fail in holding the
seal over against the corresponding sensation; like a bad archer, I miss
and fall wide of the mark--and this is called falsehood.
THEAETETUS: Yes; it is rightly so called.
SOCRATES: When, therefore, perception is present to one of the seals
or impressions but not to the other, and the mind fits the seal of the
absent perception on the one which is present, in any case of this sort
the mind is deceived; in a word, if our view is sound, there can be no
error or deception about things which a man does not know and has never
perceived, but only in things which are known and perceived; in these
alone opinion turns and twists about, and becomes alternately true and
false;--true when the seals and impressions of sense meet straight and
opposite--false when they go awry and crooked.
THEAETETUS: And is not that, Socrates, nobly said?
SOCRATES: Nobly! yes; but wait a little and hear the explanation, and
then you will say so with more reason; for to think truly is noble and
to be deceived is base.
THEAETETUS: Undoubtedly.
SOCRATES: And the origin of truth and error is as follows:--When the wax
in the soul of any one is deep and abundant, and smooth and perfectly
tempered, then the impressions which pass through the senses and sink
into the heart of the soul, as Homer says in a parable, meaning to
indicate the likeness of the soul to wax (Kerh Kerhos); these, I say,
being pure and clear, and having a sufficient depth of wax, are also
lasting, and minds, such as these, easily learn and easily retain,