_Socr._ We must speak thus on this subject, defining it from the
beginning: It is impossible that he who knows any thing, and has a
remembrance of it in his soul, but does not actually perceive it, can
think that it is some other thing that he knows, of which he has the
impression, though he does not perceive it: and again, it is impossible
that any one can think that what he knows is that which he does not
know, and of which he has not the seal: or that what he does not know is
that which he does not know: or that what he does not know is that which
he does know: or think that what he perceives is some other thing that
he perceives: or that what he perceives is something that he does not
perceive: or that what he does not perceive is some other thing that he
does not perceive: or that what he does not perceive is something that
he does perceive. And again it is still more impossible, if that can be,
that a person should think that what he knows and perceives, and of
which he has an impression by means of perception, is something else
that he knows and perceives, and of which in like manner he has an
impression by means of perception. And it is impossible that what he
knows and perceives, and of which he has a correct remembrance, he can
think is something else that he knows: or that what he knows and
perceives, and in like manner retains in his remembrance, is something
else that he perceives: or again, that what he neither knows nor
perceives is something else that he neither knows nor perceives: or that
what he neither knows nor perceives is something else that he does not
know; or that what he neither knows nor perceives is something else that
he does not perceive. In all these cases it is utterly impossible for
any one to judge falsely. It remains, therefore, that it must take
place, if anywhere, in the following cases.
120. _Theæ._ In what cases? perhaps I shall understand you better from
them; for at present I do not follow you.
_Socr._ In things which a person knows, he may think that they are
different from the things that he knows and perceives; or from those
which he does not know, but perceives; or that the things which he knows
and perceives are some of the things which he likewise knows and
perceives.
_Theæ._ Now I am left much further behind than I was.
_Socr._ Listen again, then, as follows: I, knowing Theodorus, and
remembering within myself what kind of a person he is, and in like
manner, Theætetus, do I not sometimes see them, and sometimes not, and
sometimes touch them, and sometimes not, and hear or perceive them by
some other sense, but sometimes have I no perception of you at all, yet
nevertheless do I remember you, and know you within myself?
_Theæ._ Certainly.
_Socr._ Understand this, then, the first of the things that I wish to
prove, that it is possible for a man not to perceive what he knows, and
that it is possible for him to perceive it.
_Theæ._ True.
_Socr._ And does it not often happen that a man does not perceive what
he does not know, and often that he perceives it only?
_Theæ._ This also is true.
121. Consider then, whether you can now follow me better. Socrates knows
Theodorus and Theætetus, but he sees neither of them, nor has he any
other perception respecting them, now he can never form this judgment
within himself, that Theætetus is Theodorus? Do I say any thing to the
purpose or not?
_Theæ._ Yes, quite true.
_Socr._ This then was the first of the cases that I mentioned.
_Theæ._ It was.
_Socr._ But the second was this, that I knowing one of you, but not
knowing the other, and perceiving neither, should never think that he
whom I know is the person whom I do not know.
_Theæ._ Right.
_Socr._ The third was this, that I neither knowing nor perceiving either
of them, should not think that he whom I do not know is some other
person of those whom I do not know: and consider that you again hear in
succession all the instances before put, in which I shall never form a
false judgment respecting you and Theodorus, neither while knowing nor
ignorant of you both, nor while knowing one, and not the other; and in
the same way with regard to perceptions, if you follow me.
_Theæ._ I do follow you.
122. _Socr._ It remains, therefore, that I may form a false judgment in
this case, when knowing you and Theodorus, and having the impression of
both of you in that waxen tablet made by a seal ring as it were, seeing
you both from a distance and not sufficiently distinguishing you, I
endeavour, by attributing the peculiar impression of each to his
peculiar aspect, applying it so as to adapt it to its own form in order
that I may recognise it, then failing in this, and changing them like
those that put their shoes on the wrong feet, I fit the aspect of each
to the impression of the other, as happens in looking into mirrors,
where the sight passes from the right to the left, so I fall into the
same error; then mistaken opinion and false judgment take place.
_Theæ._ What happens with regard to judgment, Socrates, seems
wonderfully like what you describe.
_Socr._ Still further, when, knowing both of you, in addition to knowing
I perceive one, but not the other, I have a knowledge of the other not
according to perception, which I thus described before, but you did not
then understand me.
_Theæ._ I did not.
123. _Socr._ I said this however, that a person who knows and perceives
one and has a knowledge of him according to perception, will never think
that he is some other person whom he knows and perceives, and of whom he
has a knowledge according to perception. Was not this what I said?
_Theæ._ Yes.
_Socr._ There remained then the case that was just now mentioned, in
which we said that false judgment takes place, when a person knowing you
both and seeing you both, or having some other perception of you both,
has not the impression of each according to the perception of each, but,
like an unskilful archer, shoots beside the mark and misses, this then
is called a falsehood.
_Theæ._ And very properly so.
_Socr._ When, therefore, perception is present to one of the
impressions, and not to the other, and the one applies the impression of
the absent perception to that which is present, in this case the mind is
altogether deceived: and, in a word, with respect to things that a
person has neither known nor ever perceived, it is not possible, as it
seems, either to be deceived, or to form a false judgment, if there is
any soundness in what we now say: but with respect to things that we
know and perceive, in these very things judgment is conversant and turns
round, becoming both false and true, by collecting together in a direct
and straight line the copies and marks proper to each, it is true, but
sideways and obliquely, false.