Ursula K. Le Guin — The Ursula K. Le Guin Prize for Fiction

In the same way, the purer the invention, the more important is its credibility, consistency, coherence. The rules of the invented realm must be followed to the letter.

that is a good description not only of the piece itself, but of the characteristic narrative ploy of science fiction: to be sober in imagining and to tell the incredible credibly.

Fantasy not only asks “What if things didn’t go on just as they do?” but demonstrates what they might be like if they went otherwise—thus gnawing at the very foundation of the belief that things have to be the way they are.