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.

When we perceive any object of a familiar kind, much of what appears subjectively to be immediately given is really derived from past experience.

Beggars do not envy millionaires, though of course they will envy other beggars who are more successful.

The first step in wisdom, as well as in morality, is to open the windows of the ego as wide as possible.

Much that passes as idealism is disguised hatred or disguised love of power.

Adventurous men enjoy shipwrecks, mutinies, earthquakes, conflagrations, and all kinds of unpleasant experiences. They say to themselves, for example, 'So this is what an earthquake is like,' and it gives them pleasure to have their knowledge of the world increased by this new item.

I am as drunk as a lord, but then, I am one, so what does it matter ?