Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering.

The dinosaurs disappeared because they could not adapt to their changing environment. We shall disappear if we cannot adapt to an environment that now contains spaceships, computers — and thermonuclear weapons.

Perhaps our role on this planet is not to worship God — but to create Him.

Behind every man now alive stand 30 ghosts, for that is the ratio by which the dead outnumber the living.