I had supposed until that time that it was quite common for parents to love their children, but the war persuaded me that it is a rare exception. I had supposed that most people liked money better than almost anything else, but I discovered that they liked destruction even better. I had supposed that intellectuals frequently loved truth, but I found here again that not ten per cent of them prefer truth to popularity.

But as the work proceeded I was continually reminded of the fable about the elephant and the tortoise. Having constructed an elephant upon which the mathematical world could rest, I found the elephant tottering, and proceeded to construct a tortoise to keep the elephant from falling. But the tortoise was not more secure than the elephant, and after some twenty years of very arduous toil, I came to the conclusion that there was nothing more that I could do in the way of making mathematical knowledge indubitable.

Next to worry probably one of the most potent causes of unhappiness is envy.

In America everybody is of the opinion that he has no social superiors, since all men are equal, but he does not admit that he has no social inferiors, for, from the time of Jefferson onward, the doctrine that all men are equal applies only upwards, not downwards.

A good social system is not to be secured by making people unselfish, but, by making their own vital impulses fit in with other peoples. This is feasible. Those who have produced stoic philosophies have all had enough to eat and drink. I feel I shall find the truth on my deathbed and be surrounded by people too stupid to understand—fussing about medicines instead of searching for wisdom. I hate being all tidy like a book in a library where nobody reads – prison is horribly like that.

If an opinion contrary to your own makes you angry, that is a sign that you are subsciously aware of having no good reason for thinking as you do. [...] The most savage controversies are those about matters as to which there is no good evidence either way. Persecution is used in theology, not in arithmetic, because in arithmetic there is knowledge, but in theology there is only opinion. So whenever you find yourself getting angry about a difference of opinion, be on your guard; you will probably find, on examination, that your belief is going beyond what the evidence warrants.

There may be no good reasons for very many opinions that are held with passion.