The more I study the things of the mind the more mathematical I find them. In them as in mathematics it is a question of quantities; they must be treated with precision. I have never had more satisfaction than in proving this in the realms of art, politics and history.

To have a true idea of man or of life, one must have stood himself on the brink of suicide, or on the door-sill of insanity, at least once.

History is nothing but a problem of mechanics applied to psychology.

I wish to reproduce things as they are or as they would be even if I myself did not exist.

His tongue is by turns a sponge, a brush, a comb. He cleans himself, he smooths himself, he knows what is proper.

The search for causes must come after the collection of facts.

A fixed idea is like the iron rod which sculptors put in their statues. It impales and sustains.