"Racism, pollution and the rest of it are themselves very close to extinction."

"I am the only guinea pig I have."

"Sometimes I think we're alone. Sometimes I think we're not. In either case, the thought is staggering."

"Nature is trying very hard to make us succeed, but nature does not depend on us. We are not the only experiment."

"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong."

"Now there is one outstandingly important fact regarding Spaceship Earth, and that is that no instruction book came with it."

"A good garden may have some weeds."

"The mystery of love is greater than the mystery of death."

"I submit to you that if a man hasn't discovered something he will die for, he isn't fit to live."

"It is better to be prepared for an opportunity and not have one than to have an opportunity and not be prepared."

"It's not the men in my life that count, it's the life in my men."

"Too often we... enjoy the comfort of opinion without the discomfort of thought."