Terry Pratchett

As I have discovered by examining my past, I started out as a child. Coincidentally, so did my brother. My mother did not put all her eggs in one basket, so to speak: she gave me a younger brother named Russell, who taught me what was meant by 'survival of the fittest.'

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.