Retrospective determinism is the logical fallacy that because something happened, it was therefore bound to happen; the term was coined by the French philosopher Henri Bergson. For example:
This argument gives no logical grounds to conclude Caesar's assassination was the only possible outcome, or even the most likely outcome of the circumstances. Simply asserting this is committing the fallacy of retrospective determinism. This type of fallacy is often used as a build-up to a hasty generalization: because something happened in given circumstances, it was not only bound to happen, but will in fact always happen given those circumstances. For example:
This not only does not follow on logical grounds, but is false: a dictator may be murdered by a political rival, killed in a war with a foreign power, or simply die by accident or natural causes. Discounting these possibilities, it still does not follow that any dictator, if they lived long enough, would be assassinated because Caesar was assassinated. While the conclusion is correct, the premise is faulty. Caesar's assassination does not predict the inevitable assassination of all other dictators.