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### What is counterfactual thought?

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.

### Two poles of counterfactual thought

The two poles of the continuum are as follows:

1. The alternate world ought to be as close as possible to our world, except that the desideratum is true; we ought to start from our exact world and alter things, first of all so as to make the desideratum true, second of all so as to make the world coherent. I will call this ceteris paribus (CE) counterfactual thinking.
2. The alternate world ought to be one in which the desideratum happens naturally; we ought to alter what happens before and around the desideratum so that it is as plausible as possible within the context of the alternate world. I will call this most likely explanation (MLE) counterfactual thinking\$^2\$.

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.

### Example: What if you were a billionaire?

Consider, for instance, the hypothetical "what would you do if you were a billionaire?" The two poles would look like this:

1. 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.)

2. 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".