"Actually, my solution generated considerable further work and the "dog-flea" model keeps cropping up from time to time in unexpected contexts."

“There are two kinds of geniuses: the ‘ordinary’ and the ‘magicians.’ an ordinary genius is a fellow whom you and I would be just as good as, if we were only many times better. There is no mystery as to how his mind works. Once we understand what they’ve done, we feel certain that we, too, could have done it. It is different with the magicians... Feynman is a magician of the highest caliber.”

“Where there is independence there must be the normal law.”

“There are, roughly speaking, two kinds of mathematical creativity. One, akin to conquering a mountain peak, consists of solving a problem which has remained unsolved for a long time and has commanded the attention of many mathematicians. The other is exploring new territory.”

“I didn't even try to penetrate the comics, though many years later I came, somewhat grudgingly, to admire Pogo.”

“In the summer of 1930 my academic future, however, was not uppermost in my mind. I had been stricken by an acute attack of a disease which at regular intervals afflicts all mathematicians and, for that matter, all scientists: I became obsessed by a problem.”

“I prefer concrete things and I don't like to learn more about abstract stuff than I absolutely have to.”