September 12th, 2006

ozarque figure

Writing science fiction; probability/plausibility constraints...

My e-mail this morning included an off-LJ comment from Douglas Dee that (with his permission) I want to share with you. Here's the comment:

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I liked your poem "The Star-Spangled Ballot." The absurdity of the premise doesn't bother me. As you said, there's no law "that the premise of an sf poem must be probable." I think for some readers the problem was that the specific near-future setting led them to expect something plausible, and thus the poem contradicted their expectations.

You complained once that some people pointed out your "error" in having a fictional 24th amendment (effective 1991) in _Native Tongue_ , when there is a real 24th amendment (effective 1964). The fact that this is an SF novel set in the future [the main action taking place in the late 22nd century, if my skimming of the book was not misleading] sets up an expectation in the readers' minds that the history of the fictional world is essentially the same as the real world up until roughly the time you wrote the book. Hence, a divergence in the 1960s or earlier contradicts the readers' expectations and leads them to suspect you just made a mistake, or else just makes them feel perplexed.

If I wrote a what-if-the-South-had-won-the-Civil-War book, no readers would complain that I was "wrong" about the outcome of the battle of Gettysburg. It's part of their expectation that that would be different. However, if in the book I made a false statement about the life of Julius Caesar, readers would think I made a mistake, since they would assume an implicit understanding that the book-world's history was the same as ours until the presumed point of divergence during the American Civil War.
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This comment seems to me to include an interesting hypothesis.

Douglas and I agree that there's no law requiring the premise of an sf poem to be probable. (And I suspect we'd agree that that extrapolates, and there's no law that the premise of a science fiction narrative in any genre must be probable.) "Plausible" is of course a different matter: That which is probable is not-unlikely-to-happen; that which is plausible also has to be not-unlikely-to-happen, but in addition it has to make sense. It has to meet the requirement of Internal Consistency, however inconsistent it might be with external facts and circumstances, or it's not plausible.

The additional hypothesis introduced in the comment, if I'm understanding it correctly, adds yet another constraint: An sf narrative in the "alternate history" subgenre isn't plausible unless the history of the fictional world is essentially the same as the history of the real world up until (a) roughly the time when the narrative is written, and/or (b) roughly the time when the history in the narrative diverges from the history of the real world.

Is that a valid hypothesis? Is it a valid constraint on writing alternate history in sf?