We know that the exercise of virtue should be its own reward, and it seems to follow that the enduring of it on the part of the patient should be its own punishment.

A life without adventure is likely to be unsatisfying, but a life in which adventure is allowed to take whatever form it will is sure to be short.

The most essential characteristic of scientific technique is that it proceeds from experiment, not from tradition. The experimental habit of mind is a difficult one for most people to maintain; indeed, the science of one generation has already become the tradition of the next

Reason may be a small force, but it is constant, and works always in one direction, while the forces of unreason destroy one another in futile strife.

I used often to go to America during Prohibition, and there was far more drunkenness there then than before; the prohibition of pornography has much the same effect.

Vanity is a motive of immense potency.

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.