Our challenge is to give what account we can of what becomes of life in the solar system, this corner of the universe that is our home; and, most of all, what becomes of men-all men, of all nations, colors, and creeds. This has become one world, a world for all men. It is only such a world that can now offer us life, and the chance to go on.

I tell my students to try early in life to find an unattainable objective.

There is nothing worth having that can he obtained by nuclear war - nothing material or ideological - no tradition that it can defend. It is utterly self-defeating.

Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.

A scientist should be the happiest of men. Not that science isn't serious; but as everyone knows, being serious is one way of being happy, just as being gay is one way of being unhappy.

I think all of you know there is no adequate defense against massive nuclear attack.

The Vietnamese have a secret weapon. It's their willingness to die beyond our willingness to kill. In effect, they've been saying, You can kill us, but you'll have to kill a lot of us; you may have to kill all of us. And, thank heaven, we are not yet ready to do that.