A fanatic is a man who, when he's lost sight of his purpose, redoubles his effort.

At each stage...entirely new laws, concepts and generalizations are necessary, requiring inspiration and creativity to just as great a degree as in the previous one.

The fish that first ventured ashore had considerable practical problems.

It is a truism that the structure of a society is basically determined by its technology. Not in an absolute sense-there may be totally different cultures using identical tools-but the tools settle the possibilities; you can't have interstellar trade without spaceships. A race limited to a single planet, possessing a high knowledge of mechanics but with its basic machines of industry and war requiring a large capital investment, will inevitably tend toward collectivism under one name or another. Free enterprise needs elbow room.

Heaven is not as narrowly literal-minded as hell.

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.

So much American science fiction is parochial - not as true now as it was years ago, but the assumption is one culture in the future, more or less like ours, and with the same ideals, the same notions of how to do things, just bigger and flashier technology. Well, you know darn well it doesn't work that way.