A man sufficiently gifted with humor is in small danger of succumbing to flattering delusions about himself, because he cannot help perceiving what a pompous ass he would become if he did.

Evil, by definition, is that which endangers the good, and the good is that which we perceive as a value.

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.

Scientific truth is universal, because it is only discovered by the human brain and not made by it, as art is.

The human soul is very much older than the human mind.

All living beings have received their weapons through the same process of evolution that moulded their impulses and inhibitions; for the structural plan of the body and the system of behaviour of a species are parts of the same whole.... Wordsworth is right: there is only one being in possession of weapons which do not grow on his body and of whose working plan, therefore, the instincts of his species know nothing and in the usage of which he has no correspondingly adequate inhibition.

I believe that present day civilized man suffers from insufficient discharge of his aggressive drive