SOCRATES: Capital, Theaetetus; and about this there shall be no dispute,
because I want you to grow; but there is another difficulty coming, which
you will also have to repulse.

THEAETETUS: What is it?

SOCRATES: Some one will say, Can a man who has ever known anything, and
still has and preserves a memory of that which he knows, not know that
which he remembers at the time when he remembers? I have, I fear, a
tedious way of putting a simple question, which is only, whether a man who
has learned, and remembers, can fail to know?

THEAETETUS: Impossible, Socrates; the supposition is monstrous.

SOCRATES: Am I talking nonsense, then? Think: is not seeing perceiving,
and is not sight perception?

THEAETETUS: True.

SOCRATES: And if our recent definition holds, every man knows that which
he has seen?

THEAETETUS: Yes.

SOCRATES: And you would admit that there is such a thing as memory?

THEAETETUS: Yes.

SOCRATES: And is memory of something or of nothing?