Beauty as we feel it is something indescribable; what it is or what it means can never be said.

Knowledge is not eating, and we cannot expect to devour and possess what we mean. Knowledge is recognition of something absent; it is a salutation, not an embrace.

Eternal vigilance is the price of knowledge.

It is a great advantage for a system of philosophy to be substantially true.

Old age is as forgetful as youth, and more incorrigible; it displays the same inattentiveness to conditions; its memory becomes self-repeating and degenerates into an instinctive reaction, like a bird's chirp.

Man is a fighting animal; his thoughts are his banners, and it is a failure of nerve in him if they are only thoughts.

Sex endows the individual with a dumb and powerful instinct, which carries his body and soul continually towards another, makes it one of the dearest employments of his life to select and pursue a companion, and joins to possession the keenest pleasure, to rivalry the fiercest rage, and to solicitude an eternal melancholy. What more could be needed to suffuse the world with the deepest meaning and beauty?