When one admits that nothing is certain one must, I think, also admit that some things are much more nearly certain than others.

The key to happiness is accepting one unpleasant reality every day.

We need a science to save us from science.

Altogether it will be found that a quiet life is characteristic of great men, and that their pleasures have not been of the sort that would look exciting to the outward eye.

Fundamental happiness depends more than anything else upon what may be called a friendly interest in persons and things.

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.

Pure mathematics consists entirely of assertions to the effect that, if such and such a proposition is true of anything, then suchand such another proposition is true of that thing.... Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true.