Steve Martin

I realized that comedians of the day were operating on jokes and punch lines. The moment you say the punch line, the audience either laughs sincerely or they laugh automatically or they don't laugh. The thing that bothered me was that automatic laugh. I said, that's not real laughter.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.