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

When asked for advice by beginners. Know your ending, I say, or the river of your story may finally sink into the desert sands and never reach the sea.

The fall of Empire, gentlemen, is a massive thing, however, and not easily fought. It is dictated by a rising bureaucracy, a receding initiative, a freezing of caste, a damming of curiosity — a hundred other factors. It has been going on, as I have said, for centuries, and it is too majestic and massive a movement to stop.

I'm gradually managing to cram my mind more and more full of things. I've got this beautiful mind and it's going to die, and it'll all be gone. And then I say, not in my case. Every idea I've ever had I've written down, and it's all there on paper. And I won't be gone; it'll be there.

Since emotions are few and reasons are many (said the robot Giscard) the behavior of a crowd can be more easily predicted than the behavior of one person.

Fertility is hereditary. If your parents didn't have any children, neither will you. I do not fear computers. I fear the lack of them.

Scientific apparatus offers a window to knowledge, but as they grow more elaborate, scientists spend ever more time washing the windows.