STRANGER: The art of discerning or discriminating.

THEAETETUS: Very good.

STRANGER: Think whether you cannot divide this.

THEAETETUS: I should have to think a long while.

STRANGER: In all the previously named processes either like has been
separated from like or the better from the worse.

THEAETETUS: I see now what you mean.

STRANGER: There is no name for the first kind of separation; of the
second, which throws away the worse and preserves the better, I do know a
name.

THEAETETUS: What is it?

STRANGER: Every discernment or discrimination of that kind, as I have
observed, is called a purification.

THEAETETUS: Yes, that is the usual expression.

STRANGER: And any one may see that purification is of two kinds.

THEAETETUS: Perhaps so, if he were allowed time to think; but I do not see
at this moment.