For purposes of action nothing is more useful than narrowness of thought combined with energy of will.

Conquering any difficulty always gives one a secret joy, for it means pushing back a boundary-line and adding to one's liberty.

The man who has no inner-life is a slave to his surroundings.

Self-interest is but the survival of the animal in us. Humanity only begins for man with self-surrender.

Thought is a kind of opium; it can intoxicate us, while still broad awake; it can make transparent the mountains and everything that exists.