There are some men who are counted great because they represent the actuality of their own age, and mirror it as it is. Such an one was Voltaire, of whom it was epigrammatically said: "he expressed everybody's thoughts better than anyone." But there are other men who attain greatness because they embody the potentiality of their own day and magically reflect the future. They express the thoughts which will be everybody's two or three centuries after them. Such as one was Descartes.

The secret of genius is to carry the spirit of childhood into maturity.

History warns us that it is the customary fate of new truths to begin as heresies and to end as superstitions.

I am too much of a sceptic to deny the possibility of anything...

To a clear eye the smallest fact is a window through which the infinite may be seen.

The rules of the game are what we call the laws of nature.

Science and literature are not two things, but two sides of one thing.