Night will always be a time of fear and insecurity, and the heart will sink with the sun.

A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.

The significant chemicals of living tissue are rickety and unstable, which is exactly what is needed for life.

Any planet is 'Earth' to those that live on it.

All of a sudden, space isn't friendly. All of a sudden, it's a place where people can die. . . . Many more people are going to die. But we can't explore space if the requirement is that there be no casualties; we can't do anything if the requirement is that there be no casualties.

It’s a poor atom blaster that won’t point both ways.

Democracy cannot survive overpopulation. Human dignity cannot survive it. Convenience and decency cannot survive it. As you put more and more people into the world, the value of life not only declines, but it disappears. It doesn't matter if someone dies.