On counterfactuals: Judea Pearl: The Book of Why: The New Science of Cause and Effect https://books.google.com/books?isbn=0465097618: "I think that his critics (and perhaps Lewis himself) missed the most important point. We do not need to argue about whether such worlds exist as physical or even metaphysical entities...
...If we aim to explain what people mean by saying “A causes B,” we need only postulate that people are capable of generating alternative worlds in their heads, judging which world is “closer” to ours and, most importantly, doing it coherently so as to form a consensus. Surely we could not communicate about counterfactuals if one person’s “closer” was another person’s “farther.” In this view, Lewis’s appeal “Why not take counterfactuals at face value?” called not for metaphysics but for attention to the amazing uniformity of the architecture of the human mind.
As a licensed Whiggish philosopher, I can explain this consistency quite well: it stems from the fact that we experience the same world and share the same mental model of its causal structure. We talked about this all the way back in Chapter 1. Our shared mental models bind us together into communities. We can therefore judge closeness not by some metaphysical notion of “similarity” but by how much we must take apart and perturb our shared model before it satisfies a given hypothetical condition that is contrary to fact (Joe not taking aspirin).
In structural models we do a very similar thing, albeit embellished with more mathematical detail. We evaluate expressions like “had X been x” in the same way that we handled interventions do( X = x), by deleting arrows in a causal diagram or equations in a structural model. We can describe this as making the minimal alteration to a causal diagram needed to ensure that X equals x. In this respect, structural counterfactuals are compatible with Lewis’s idea of the most similar possible world...
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