I think that I have always had a basic liking for the natural numbers. To me they are the one real thing. We can conceive of a chemistry that is different from ours, or a biology, but we cannot conceive of a different mathematics of numbers. What is proved about numbers will be a fact in any universe.

In: D. Albers, G. Alexanderson and C. Reid, More Mathematical People: Contemporary Conversations (p. 264)