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Prompted by this interview (which is interesting, but there should be a trigger warning for pompousness attached to Unger, even if I agree with most of his points about the virtues of the concrete), I looked up David Lewis. "Possible worlds" reminds me of the talk about Everett branches here. Neither is particularly useful.
Pretty sure Lewis' stuff generalizes the dominant paradigm for causal inference today.
It's too bad all the people who know how to do philosophy are too busy posting on reddit subforums.