On Marc's New Incompatibilist Argument
\ (3) CS differs > A<>The conclusion (3) favors incompatibilism, though exactly what it says depends on some choices of interpretation. >
supposed to be a future action of mine.
So (3)’s obvious counterfactual reading is, “If my CS were quite
different from what it actually is, I would do A.”
Considered as an ordinary subjunctive, the
latter seems truth-valueless; assuming only that my CS is quite
saying nothing about any specific differences or even types of
can (even under determinism) project nothing about my doing or my not
A. But in order to bring out the
conflict between (3) and compatibilism, we must read it, rather, as a
semifactual: “(Even) if my CS were quite different from what it
actually is, I
would (still) do A,” the idea being loosely that A would happen
my CS and hence is out of my control.
(Note that semifactuals differ logically from ordinary counterfactuals. E.g., all known counterexamples to Contraposition for subjunctives are semifactuals.<1>)
What if we now take A to be a past action of mine instead of a future one? Then it would read, “(Even) if my CS had been quite different from what it actually is, I would (still) have done A.” This seems to pose the same threat to compatibilism, whatever threat that is, so apparently the tense doesn’t matter.
It’s a good thing for the argument that (3) needs to be read semifactually, because each of the premises is obviously semifactual too. If (3) were an ordinary counterfactual while (1) and (2) were semifactuals, we could well doubt the argument’s validity on the grounds that a different similarity relation was mobilized as between premises and conclusion.
as things are, the argument is intuively valid.
And any standard similarity semantics would make the argument
long as there was no other reason why the similarity relation might
between the premises and the conclusion.
For simplicity, I assume Stalnaker semantics (Lewis’ semantics
only in that he abandons the Limit Assumption, and I see no relevance
to the free-will issue): At the closest
CS-differing world, S; at the closest CS-differing world, S É A; therefore, at the closest CS-differing
world, A (duh).
Premise (1) says that even if my CS were
different, S would still have obtained.
But under determinism, that is clearly false: Had anything
that is a
partial cause of A not obtained, then the initial conditions that were
causes of that thing would have had to differ all the way back to the
Big Bang. (Though (2) remains true, since
it holds by
law of nature alone.) Thus, the argument
does not show that free will is incompatible with determinism,
which was its primary objective.
What about (1) under indeterminism? (1) is no longer clearly false, because the laws no longer logically force initial conditions to have been different given that CS was. But I see no reason to accept (1), even so. (1) would now seem either truth-valueless, because of the vagueness of its antecedent, or very probably false given the (always problematic) view that a “quasi-” or “near”-determinism holds “at the macro- level.”
(2) no longer holds by law of nature alone, for S & ~A is now logically compatible with the laws. One may say that (2) is still very probable, given the macro-quasi-determinism assumption. (Objection: That assumption would also apply to the relation between my actual CS and S. If, however improbably, S would have been the same even if my CS had differed, can we then say that A would still have been the same? Reply: Very probably, yes, because S horseshoe A is still overwhelmingly probabilified by the laws regardless of my CS.)