"I think I am a verb."

"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."

"Either war is obsolete or men are."

"Humanity is acquiring all the right technology for all the wrong reasons."

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

"In all our efforts to provide 'advantages' we have actually produced the busiest, most competitive, highly pressured, and over-organized generation of youngsters in our history."

"For my own part, having had much trouble in growing old, I am in no hurry to grow young again."

"There is no substitute for victory."

"I have a new philosophy. I'm only going to dread one day at a time."

"I bought a cactus. A week later it died. And I got depressed, because I thought, Damn. I am less nurturing than a desert."

"Therapy? I don't need that. The roles that I choose are my therapy."