Theaet. Of course.
Soc. What shall we say then? When a man has a false opinion does
he think that which he knows to be some other thing which he knows,
and knowing both, is he at the same time ignorant of both?
Theaet. That, Socrates, is impossible.
Soc. But perhaps he thinks of something which he does not know as
some other thing which he does not know; for example, he knows neither
Theaetetus nor Socrates, and yet he fancies that Theaetetus is
Socrates, or Socrates Theaetetus?
Theaet. How can he?
Soc. But surely he cannot suppose what he knows to be what he does
not know, or what he does not know to be what he knows?
Theaet. That would be monstrous.
Soc. Where, then, is false opinion? For if all things are either
known or unknown, there can be no opinion which is not comprehended
under this alternative, and so false opinion is excluded.
Theaes. Most true.
Soc. Suppose that we remove the question out of the sphere of
knowing or not knowing, into that of being and not-being.
Theaet. What do you mean?
Soc. May we not suspect the simple truth to be that he who thinks
about anything, that which. is not, will necessarily think what is
false, whatever in other respects may be the state of his mind?
Theaet. That, again, is not unlikely, Socrates.
Soc. Then suppose some one to say to us, Theaetetus:-Is it
possible for any man to think that which is not, either as a
self-existent substance or as a predicate of something else? And
suppose that we answer, "Yes, he can, when he thinks what is not
true."-That will be our answer?
Soc. But is there any parallel to this?
Theaet. What do you mean?
Soc. Can a man see something and yet see nothing?
Soc. But if he sees any one thing, he sees something that exists. Do
you suppose that what is one is ever to be found among nonexisting
Theaet. I do not.
Soc. He then who sees some one thing, sees something which is?
Soc. And he who hears anything, hears some one thing, and hears that
Soc. And he who touches anything, touches something which is one and
Theaet. That again is true.
Soc. And does not he who thinks, think some one thing?
Soc. And does not he who thinks some one thing, think something
Theaet. I agree.
Soc. Then he who thinks of that which is not, thinks of nothing?
Soc. And he who thinks of nothing, does not think at all?
Soc. Then no one can think that which is not, either as a
self-existent substance or as a predicate of something else?
Theaet. Clearly not.
Soc. Then to think falsely is different from thinking that which
Theaet. It would seem so.
Soc. Then false opinion has no existence in us, either in the sphere
of being or of knowledge?
Theaet. Certainly not.