Richard Feynman, Surely You're Joking, Mr. Feynman!: Adventures of a Curious Character

"All the time you're saying to yourself, 'I could do that, but I won't,' — which is just another way of saying that you can't."

"I couldn't claim that I was smarter than sixty-five other guys--but the average of sixty-five other guys, certainly!"

"All the time you're saying to yourself, 'I could do that, but I won't,' — which is just another way of saying that you can't."

"All the time you're saying to yourself, 'I could do that, but I won't,' — which is just another way of saying that you can't."