A handy short definition of almost all science fiction might read: realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method.

Secrecy is the keystone to all tyranny. Not force, but secrecy and censorship. When any government or church for that matter, undertakes to say to its subjects, "This you may not read, this you must not know," the end result is tyranny and oppression, no matter how holy the motives. Mighty little force is needed to control a man who has been hoodwinked in this fashion; contrariwise, no amount of force can control a free man, whose mind is free. No, not the rack nor the atomic bomb, not anything. You can't conquer a free man; the most you can do is kill him.

Money is a powerful aphrodisiac but flowers work almost as well.

When the need arises - and it does - you must be able to shoot your own dog. Don't farm it out — that doesn't make it nicer, it makes it worse.

When one teaches, two learn.

My folks tried to make a preacher of me and missed by a narrow margin… I would have made a good one if I hadn’t fallen into the fatal folly of reading anything I could lay hands on. With just a touch more self confidence and a liberal helping of ignorance I could have been a famous evangelist.

What are the facts? Again and again and again – what are the facts? Shun wishful thinking, ignore divine revelation, forget what “the stars foretell,” avoid opinion, care not what the neighbors think, never mind the unguessable “verdict of history” – what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!