Jeffrey Zeldman

Historians and scholars have access to every issue of every newspaper and journal written during the civil rights struggle of the 1960s but can access only a comparative handful of papers covering the election of Barack Obama.

Though builders may build, in the main they follow the plans of architects. Teachers teach, but they must have a text. Politicians govern, but only upon the flow of commentary that raises them up or casts them down.

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.