It seems to me that God is a convenient invention of the human mind

I have never written a book that didn't teach me far more than it taught my reader.

God, how that stings! I've spent a lifetime loving science fiction and now I find that you must expect nothing of something that's just science fiction.

In all the known history of Mankind, advances have been made primarily in physical technology; in the capacity of handling the inanimate world about Man. Control of self and society has been left to to chance or to the vague gropings of intuitive ethical systems based on inspiration and emotion. As a result no culture of greater stability than about fifty-five percent has ever existed, and these only as the result of great human misery.

Nothing interferes with my concentration. You could put on an orgy in my office and I wouldn't look up. Well, maybe once.

At two-tenths the speed of light, dust and atoms might not do significant damage even in a voyage of 40 years, but the faster you go, the worse it is--space begins to become abrasive. When you begin to approach the speed of light, hydrogen atoms become cosmic-ray particles, and they will fry the crew. ...So 60,000 kilometers per second may be the practical speed limit for space travel.

Until now in world's history, whenever we've had a dark age, its been temporary and local. And other parts of the world have been doing fine. And eventually, they help you get out of the dark age. We are now facing a possible dark age which is going to be world-wide and permanent! That's not fun. That's a different thing. But once we have established many worlds, we can do whatever we want as long as we do it one world at a time.