If one lived for ever the joys of life would inevitably in the end lose their savour. As it is, they remain perennially fresh.

Science, by itself, cannot supply us with an ethic. It can show us how to achieve a given end, and it may show us that some ends cannot be achieved.

Patriots always talk of dying for their country and never of killing for their country.

From the height of their disillusionment they look down upon those whom they despise as simple souls. For my part I have no sympathy with this outlook. All disenchantment is to me a malady, which, it is true, certain circumstances may render inevitable, but which none the less, when it occurs, is to be cured as soon as possible, not to be regarded as a higher form of wisdom.

At the age of eleven, I began Euclid, with my brother as my tutor. This was one of the great events of my life, as dazzling as first love. I had not imagined there was anything so delicious in the world. From that moment until I was thirty-eight, mathematics was my chief interest and my chief source of happiness.

The more things a man is interested in, the more opportunities of happiness he has and the less he is at the mercy of fate, since if he loses one thing he can fall back upon another.

It is clear that thought is not free if the profession of certain opinions makes it impossible to earn a living.