"I don't think I'm a very good teacher. I just try to explain things clearly."

"The thing that I cannot understand is that I can't understand it."

"Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there."

"I asked him once, 'How do you tell when a mathematical argument is correct?' He said, 'If it's beautiful, it's correct.'"

"God was invented to explain mystery. God is always invented to explain those things that you do not understand."