If materialism is true, it seems to me that we cannot know that it is true. If my opinions are the result of the chemical processes going on in my brain, they are determined by the laws of chemistry, not those of logic.

Until politics are a branch of science, we shall do well to regard political and social reforms as experiments rather than short-cuts to the millennium.

We do not know, in most cases, how far social failure and success are due to heredity, and how far to environment. But environment is the easier of the two to improve.

We must learn not to take traditional morals too seriously. And it is just because even the least dogmatic of religions tends to associate itself with some kind of unalterable moral tradition, that there can be no truce between science and religion.

Teleology is like a mistress to a biologist: he cannot live without her but he's unwilling to be seen with her in public.

It was a reaction from the old idea of "protoplasm", a name which was a mere repository of ignorance.

Science is vastly more stimulating to the imagination than the classics.