Combinatorics is an honest subject. No adèles, no sigma-algebras. You count balls in a box, and you either have the right number or you haven't. You get the feeling that the result you have discovered is forever, because it's concrete. Other branches of mathematics are not so clear-cut. Functional analysis of infinite-dimensional spaces is never fully convincing; you don't get a feeling of having done an honest day's work. Don't get the wrong idea - combinatorics is not just putting balls into boxes. Counting finite sets can be a highbrow undertaking, with sophisticated techniques.

Nature imitates mathematics.

A technique is a trick that works.

The progress of mathematics can be viewed as progress from the infinite to the finite.

Stan Ulam was lazy, ... He talked too much ... He was self-centered ... . He had an overpowering personality.

How did he do it? He must be a genius!

Theorems are not to mathematics what successful courses are to a meal.