will fancy that
he knows the things about which he has been deceived?

THEAETETUS: Certainly.

SOCRATES: Then he will think that he has captured knowledge and not
ignorance?

THEAETETUS: Clearly.

SOCRATES: And thus, after going a long way round, we are once more face
to face with our original difficulty. The hero of dialectic will retort
upon us:--'O my excellent friends, he will say, laughing, if a man knows
the form of ignorance and the form of knowledge, can he think that one
of them which he knows is the other which he knows? or, if he knows
neither of them, can he think that the one which he knows not is another
which he knows not? or, if he knows one and not the other, can he think
the one which he knows to be the one which he does not know? or the one
which he does not know to be the one which he knows? or will you tell me
that there are other forms of knowledge which distinguish the right and
wrong birds, and which the owner keeps in some other aviaries or graven
on waxen blocks according to your foolish images, and which he may be
said to know while he possesses them, even though he have them not at
hand in his mind? And thus, in a perpetual circle, you will be compelled
to go round and round, and you will make no progress.' What are we to
say in reply, Theaetetus?

THEAETETUS: Indeed, Socrates, I do not know what we are to say.

SOCRATES: Are not his reproaches just, and does not the argument truly
show that we are wrong in seeking for false opinion until we know what
knowledge is; that must be first ascertained; then, the nature of false
opinion?

THEAETETUS: I cannot but agree with you, Socrates, so far as we have yet
gone.

SOCRATES: Then, once more, what shall we say that knowledge is?--for we
are not going to lose heart as yet.

THEAETETUS: Certainly, I shall not lose heart, if you do not.

SOCRATES: What definition will be most consistent with our former views?

THEAETETUS: I cannot think of any but our old one, Socrates.

SOCRATES: What was it?

THEAETETUS: Knowledge was said by us to be true opinion; and true
opinion is surely unerring, and the results which follow from it are all
noble and good.

SOCRATES: He who led the way into the river, Theaetetus, said 'The
experiment will show;' and perhaps if we go forward in the search, we
may stumble upon the thing which we are looking for; but if we stay
where we are, nothing will come to light.

THEAETETUS: Very true; let us go forward