M. F. K. Fisher

I can no more think of my own life without thinking of wine and wines and where they grew for me and why I drank them when I did and why I picked the grapes and where I opened the oldest procurable bottles, and all that, than I can remember living before I breathed.

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.