A human being is a naturally political [animal].

A friend is a second self, so that our consciousness of a friend's existence...makes us more fully conscious of our own existence.

Metaphor is halfway between the unintelligible and the commonplace.

Courage is the first of human qualities because it is the quality which guarantees the others.

The greatest of all pleasures is the pleasure of learning.

Two characteristic marks have above all others been recognized as distinguishing that which has soul in it from that which has not - movement and sensation.

That which is impossible and probable is better than that which is possible and improbable.