The success of a science fiction writer is if he can write a good read.

And because, in all the Galaxy, they had found nothing more precious than Mind, they encouraged its dawning everywhere. They became farmers in the fields of stars; they sowed, and sometimes they reaped. And sometimes, dispassionately, they had to weed.

Religion is the most malevolent of all mind viruses.

Open the pod bay doors, Hal.

It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars.

Space can be mapped and crossed and occupied without definable limit; but it can never be conquered.

I don't believe in astrology; I'm a Sagittarius and we're skeptical.