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Counterfactual thought is fundamentally about alternate worlds$^{1}$. More specifically, we are presented with a scenario to think about: what if, instead of X, we had Y?, and consider what worlds in which this desideratum (Y) held would look like.
There are, however, two poles of counterfactual thought, or fundamental assumptions about how the structure of the alternate worlds we reason about is to be formed, between which we interpolate. Unspoken differences about on this continuum tend to drive disagreements about counterfactuals, which cannot be resolved because it is tricky to make clear what exactly they are about, which is what I will attempt to do.
The two poles of the continuum are as follows:
These do not by themselves fix an alternate world to work in, but are instead tendencies that arise in figuring out how to construct the alternate world, as will be shown below.
Consider, for instance, the hypothetical "what would you do if you were a billionaire?" The two poles would look like this:
You, exactly as you are, are somehow made into a billionaire.
An answer to how this might happen might look like "several pallets of stacked hundred dollar bills appear in your garage", or "a billionaire suddenly dies and leaves you exactly a billion dollars worth of shares in some stock".
(Intuitively, I interpret "billionaire" as "having a set of reasonably liquid assets whose value is at least a billion US dollars"; any of these would satisfy that intuition. So disagreement may yet persist about not only this intuition, but how exactly the hypothetical is to be constructed; this is why I say that CE and MLE are tendencies.)
You have become a billionaire in the way you would most likely have become a billionaire. This is a form of backwards reasoning: given a state of affairs X (you're a billionaire), how did it most likely happen? An answer to this might look like "you bought a bunch of bitcoin a decade ago" or "that business you tried to start a long time ago actually took off".