I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated.

Heaven is not as narrowly literal-minded as hell.

Colonization means potential immortality for the human genus. Man's safety on Earth was never great, and it dwindles hourly. Disarmament, even world government, will not guarantee survival in an age when population presses natural resources to the limit and when the knowledge of how to work mischief on a planetary scale is ever more widely diffused among peoples who may grow ever more desperate.

Anybody can find infinite Mandelbrot figures in his navel.

In Harvest of Stars, there is this notion, not original with me of course, that it will become possible to download at least the basic aspects of a human personality into a machine program.

What five books would I like to be remembered for? Well... Tau Zero, I like that one especially. It was somewhat of a tour de force, and I think it got across what I was trying for.

Happier are all men than the dwellers in Faerie – or the gods, for that matter…Better a life like a falling star, bright across the dark, than a deathlessness that can see naught above or beyond itself…the day draws nigh when Faerie shall fade, the Erlking himself shrink to a woodland sprite and then to nothing, and the gods go under. And the worst of it is, I cannot believe it wrong that the immortals will not live forever.