In Causation: Reductionism Versus Realism, Michael Tooley proposes a thought experiment where we imagine a simple world with only two "causal laws":
For any object x, x's having property P for a temporal interval of length At either causes x to acquire property Q, or else causes x to acquire property R, but does not do both;
For any object x, x's having property S for a temporal interval of length At either causes x to acquire property Q, or else causes x to acquire property R, but does not do both.
He then asks us to imagine a case where an object a acquires both properties P and S, and go on to acquire property Q and R. The quotation goes on,
Here, a has acquired both property Q and property R, and, as a result, there are two possibilities concerning the relevant causal relations:
Pa causes Qa, and Sa causes Ra
Pa causes Ra, and Sa causes Qa
One is therefore confronted with the question of what the relevant causal relations are. Was it the possession of property P, for the appropriate interval, that caused the acquisition of property Q, and the possession of S that caused the acquisition of R? Or was it, instead, the other way around? Given a reductionist view, however, no answer is possible.
But it seems to me that the counterfactual account of causation has no problem with this. In the counterfactual world where object a never had P, for instance, the object would fail to acquire one of either Q or R. Whichever one that would have been, that's the property which would have been caused by P.
Why does Tooley believe that this analysis is impossible or inadequate?