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.

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.

Natural selection does not give any preference at all to anything that, in the long run, could be advantageous for the species but blindly rewards everything that, momentarily, affords greater procreative success.

The neuro-physiological organization which we call instinct functions in a blindly mechanical way, particularly apparent when its function goes wrong.

Every man gets a narrower and narrower field of knowledge in which he must be an expert in order to compete with other people. The specialist knows more and more about less and less and finally knows everything about nothing.

Man appears to be the missing link between anthropoid apes and human beings.

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