Do those, said he, who learn, learn what they know, or what they do not know?

Cleinias had answered Euthydemus that those who learned learn what they do not know; and he put him through a series of questions the same as before.

Do you not know letters?

He assented.

All letters?

Yes.

But when the teacher dictates to you, does he not dictate letters?

To this also he assented.

Then if you know all letters, he dictates that which you know?

This again was admitted by him.

Then, said the other, you do not learn that which he dictates; but he only who does not know letters learns?

Nay, said Cleinias; but I do learn.

Then, said he, you learn what you know, if you know all the letters?

He admitted that.

Then, he said, you were wrong in your answer.

— Plato, Euthydemus