People who think they know everything are a great annoyance to those of us who do.

No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be.

It is change, continuing change, inevitable change, that is the dominant factor in society today. No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be.

Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today - but the core of science fiction, its essence has become crucial to our salvation if we are to be saved at all.

I do not fear computers. I fear the lack of them.

I don't believe in an afterlife, so I don't have to spend my whole life fearing hell, or fearing heaven even more. For whatever the tortures of hell, I think the boredom of heaven would be even worse.

I am not a speed reader. I am a speed understander.

Humanity has the stars in its future, and that future is too important to be lost under the burden of juvenile folly and ignorant superstition.

And above all things, never think that you're not good enough yourself. A man should never think that. My belief is that in life people will take you at your own reckoning.

A subtle thought that is in error may yet give rise to fruitful inquiry that can establish truths of great value.