SOCRATES: Very good, Theodorus; you shall see how I will come to the
rescue. If a person does not attend to the meaning of terms as they are
commonly used in argument, he may be involved even in greater paradoxes
than these. Shall I explain this matter to you or to Theaetetus?

THEODORUS: To both of us, and let the younger answer; he will incur less
disgrace if he is discomfited.

SOCRATES: Then now let me ask the awful question, which is this:--Can a
man know and also not know that which he knows?

THEODORUS: How shall we answer, Theaetetus?

THEAETETUS: He cannot, I should say.

SOCRATES: He can, if you maintain that seeing is knowing. When you are
imprisoned in a well, as the saying is, and the self-assured adversary
closes one of your eyes with his hand, and asks whether you can see his
cloak with the eye which he has closed, how will you answer the inevitable
man?

THEAETETUS: I should answer, 'Not with that eye but with the other.'

SOCRATES: Then you see and do not see the same thing at the same time.

THEAETETUS: Yes, in a certain sense.

SOCRATES: None of that, he will reply; I do not ask or bid you answer in
what sense you know, but only whether you know that which you do not know.