A life without adventure is likely to be unsatisfying, but a life in which adventure is allowed to take whatever form it will is sure to be short.

Fear is the parent of cruelty, and therefore it is no wonder if cruelty and religion have gone hand-in-hand. It is because fear is at the basis of those two things. In this world we can now begin a little to understand things, and a little to master them by the help of science, which has forced its way step by step against the Christian religion, against the churches, and against the opposition of all the old precepts.

The human race may well become extinct before the end of the century. Speaking as a mathematician, I should say the odds are about three to one against survival.

To write tragedy, a man must feel tragedy. To feel tragedy, a man must be aware of the world in which he lives. Not only with his mind, but with his blood and sinews.

There can't be a practical reason for believing something that is not true.

Children, after being limbs of Satan in traditional theology and mystically illuminated angels in the minds of educational reformers, have reverted to being little devils; not theological demons inspired by the evil one, but scientific Freudian abominations inspired by the unconscious.

A man's acts are partly determined by spontaneous impulse, partly by the conscious and unconscious effects of the various groups to which he belongs.