Friday, March 14, 2008

Lewis, free will and miracles

Compatibilists like Hume accept the Principle of Alternate Possibilities (PAP): if x freely does A, then x could have refrained from doing A. However, they give a counterfactual spin to the "could have": x could have done A if and only if were x to have willed to do A, x would have done A.

Suppose now:

  1. This Humean analysis of "could have" is correct.
  2. Lewis's account of counterfactuals is correct.
  3. Determinism holds.
  4. On some non-initial occasion I could have done otherwise (in the Humean sense).
(An occasion is initial provided it happens at the first moment of time.) It follows from these that in the occasion mentioned in (4), I could have acted in such a way that a w0-miracle would have occured, where a w-miracle is a violation of the laws of w, and where w0 rigidly designates the actual world.

The argument is simple. Suppose on that occasion I did A. Let p be the proposition that on that occasion I did not do A. On Lewis's account of counterfactuals, I evaluate counterfactuals of the form "were p to hold, q would hold" by looking at worlds close to w0 but where p holds, and in a deterministic case, these worlds match the actual world up to near the time of that occasion, and but depart therefrom in a way that goes against the laws of the actual world, i.e., in a way that is w0-miraculous. Hence, "were p to hold, a w0-miracle would occur" holds, and by the Humean analysis of "could have", it follows that I could have acted in such a way that a w0-miracle would have occurred.


Mike Almeida said...

". . . it follows that I could have acted in such a way that a w0-miracle would have occurred."

But, interestingly, you cannot cause a law-breaking event nor do anything that itself is a law-breaking event. For what it's worth, I blog about the same point here,

Heath White said...

I think Lewis takes up this question in "Are We Free to Break the Laws?" I believe his point (which I only understood half-well) was that while I could have done an action which would break the laws that obtain in the actual world, those laws wouldn't have obtained had I done the alternative action, and so I wouldn't have broken any laws. Maybe this is Mike's point too.

Alexander R Pruss said...


I agree that the laws wouldn't have obtained had I done the alternative action. But that's bad enough. In the time's arrow piece that Mike quotes from, Lewis says that you can't do miracles like going faster than light. But if my argument is right, then if determinism holds and Lewis's account of counterfactuals is correct, we can do miracles of that sort. If we did them, they wouldn't be violations of laws, but that we can do them is implausible enough.

By the way, I think the post Mike links to is right, and is a powerful criticism of Lewis: Lewis doesn't have the resources to explain why an omnipotent being could break laws and why a non-omnipotent couldn't.

Kevin Timpe said...

Jim Stone has an article which, while similar in some ways to Lewis' view, gives us non-omnipotent humans the ability to do miracles--he just thinks we never, as a matter of fact, exercise this ability.

Alexander R Pruss said...

Here's a view that might be coherent. We are capable of acting counternomically, but our probability of doing so is exactly zero, so we shouldn't expect to see any such counternomic actions.