We are to regard existence as a raid or great adventure; it is to be judged, therefore, not by what calamities it encounters, but by what flag it follows and what high town it assaults. The most dangerous thing in the world is to be alive; one is always in danger of one's life. But anyone who shrinks from that is a traitor to the great scheme and experiment of being.

He may be mad, but there's method in his madness. There nearly always is method in madness. It's what drives men mad, being methodical.

All men are ordinary men; the extraordinary men are those who know it.

It is assumed that the skeptic has no bias; whereas he has a very obvious bias in favour of skepticism.

[Marxism will] in a generation or so [go] into the limbo of most heresies, but meanwhile it will have poisoned the Russian Revolution.

The true object of human life is play.

Science is the study of the admitted laws of existence, which cannot prove a universal negative about whether those laws could ever be suspended by something admittedly above them. It is as if we were to say that a lawyer was so deeply learned in the American Constitution that he knew there could never be a revolution in America.