SF Premises

A fictional narrative has to be structured in a way that a historical or biographical narrative cannot be. A novel must work towards a resolution whereas a biographical volume merely ends at the time of writing or with its subject's death. Chance events may occur in a novel but must serve the plot and therefore cannot be merely arbitrary or random and there should not be any deus ex machina. John Buchan had too many coincidences. In real life, I encountered the surnames Nichols, Nicholson and Nixon in close association with each other whereas a novelist would usually avoid such a confusing juxtaposition except maybe for comic effect.

A fellow sf reader once suggested to me that a good sequel says, "Now there is a hell of a lot that we didn't tell you before!" A good sequel can do this but should nevertheless remain aesthetically congruous with the previous volume. I think that it would be inappropriate to introduce causality violation in a sequel to The Time Machine or newly discovered faster than light interstellar travel in a sequel to any of Poul Anderson's works that are based on the premise of STL travel.

However, a future history, reflecting real history, can show technological advances. Thus, Heinlein's Future History, Anderson's Psychotechnic History and Niven's Known Space History all show an STL period followed by an FTL period. Comparing future histories is one really enjoyable aspect of reading sf.