The demand for certainty is one which is natural to man, but is nevertheless an intellectual vice. So long as men are not trained to withhold judgment in the absence of evidence, they will be led astray by cocksure prophets, and it is likely that their leaders will be either ignorant fanatics or dishonest charlatans. To endure uncertainty is difficult, but so are most of the other virtues.

At the age of eleven, I began Euclid, with my brother as my tutor. ... I had not imagined that there was anything so delicious in the world. After I had learned the fifth proposition, my brother told me that it was generally considered difficult, but I had found no difficulty whatsoever. This was the first time it had dawned on me that I might have some intelligence.

Something of the hermit's temper is an essential element in many forms of excellence, since it enables men to resist the lure of popularity, to pursue important work in spite of general indifference or hostility, and arrive at opinions which are opposed to prevalent errors.

What is new in our time is the increased power of the authorities to enforce their prejudices.

I do not think any reasonable person can doubt that in India, China and Japan, if the knowledge of birth control existed, the birthrate would fall very rapidly

My own belief is that in most ages and in most places obscure psychological forces led men to adopt systems involving quite unnecessary cruelty, and that this is still the case among the most civilized races at the present day.

For over two thousand years it has been the custom among earnest moralists to decry happiness as something degraded and unworthy