James Thurber

The appreciative smile, the chuckle, the soundless mirth, so important to the success of comedy, cannot be understood unless one sits among the audience and feels the warmth created by the quality of laughter that the audience takes home with it.

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.