Possible Histories

Alternative histories are logical possibilities. This means no more than that such histories can be imagined and contemplated without self-contradiction. Let us consider the cliched example of a German victory in World War II. A narrative describing a German victory is counter-factual in that it contradicts known history. However, such an account is not internally inconsistent or self-contradictory. This is all that is meant by logical possibility.

However, the proposition that alternative histories are logically possible might still have two different meanings. It might mean either that:

(i) Hitler could have won World War II;

or that:

(ii) there could be a parallel universe in which Hitler did win World War II.

(i) and (ii) are not the same proposition. A novel could be based on premise (i). If challenged on the counter-factual status of his narrative, the author might reply not that his novel is set in a parallel universe - this would be premise (ii) - but simply that all fictional narratives describe events that did not happen in any case.

A short story or novel that is set entirely within an alternative history might be an example of:

(i) this did not happen or
(ii) this did happen in another universe -

- except that the "did happen" in (ii) is fictional in any case.

Poul Anderson's "The House of Sorrows" could be (i) or (ii). However, much alternative history fiction describes (highly improbable) travel between universes and therefore is premise (ii). SM Stirling's Draka series definitely becomes premise (ii) only in Volume IV.