Machines can only find what ignorant men have programmed them to find.

A fanatic's willingness to kill or be killed in the service of a cause cannot prove the rightness of that cause.

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.

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.

Better a life like a falling star, brief bright across the dark, than the long, long waiting of the immortals, loveless and cheerlessly wise.

There are some ideas so stupid that only intellectuals can believe in them, particularly left-wing intellectuals.

Heaven is not as narrowly literal-minded as hell.