If there is no contradictory impression, there is nothing to awaken reflection

Let no-one ignorant of geometry enter. Said to have been inscribed above the door of Plato's Academy.

He who is not a good servant will not be a good master.

The ludicrous state of solid geometry made me pass over this branch.

... what we can be positive about is what we have just said, namely that they must be given the right education, whatever that may be, as the surest way to make them behave humanely to each other and the subjects in their charge.

By education I mean that training in excellence from youth upward which makes a man passionately desire to be a perfect citizen, and teaches him to rule, and to obey, with justice. This is the only education which deserves the name.

Truth is its own reward.