In challenging a kzin, a simple scream of rage is sufficient. You scream and you leap.

I never got good at predicting what millions of people will suddenly decide is rational.

SF isn't a genre; SF is the matrix in which genres are embedded, and because the SF field is never going in any one direction at any one time, there is hardly a way to cut it off.

In the world of words the imagination is one of the forces of nature.

And every friend I've got has been writing Mars stories. It was pretty clear I'd never catch up.

One mark of a good officer, he remembered, was the ability to make quick decisions. If they happen to be right, so much the better.

I've spent a lot of my life among people brighter than myself.