I was talking to Eliza Block the other day about ‘irrelevant’ counterfactuals, counterfactuals where the antecedent is intuitively irrelevant to the consequent, and by the end I was wondering why anyone should think there’s a serious problem here. In case I forget why this is so, I’ll write it down. (I can’t remember how many of these ideas were Eliza’s, or even which she agreed with, or which ideas are completely familiar, hence the somewhat cautious statement of where this all came from.)

So the problem cases are meant to be things like.

(1) Had I driven from Berlin to Moscow this summer, Churchill would have been Prime Minister of Britain during WWII.

Clearly there is something wrong in a Gricean sense with (1). But is there a semantic problem with (1)? I.e. is it false? If so Lewis’s theory of counterfactuals has a problem, since (1) is true on Lewis’s theory. It seems to me the answer to that is *no*, (1) is pretty clearly true. Here’s the argument for that.

First, (2) seems to be true.

(2) Had I driven from Berlin to Moscow this summer, I would have driven from the city where Hitler died to the city where Stalin died.

(I hope my history facts are right here – otherwise make relevant substitutions.)

Moreover, if (2) is true then (3), which just involves filling out the details of the relevant deaths in some detail, is true.

(3) Had I driven from Berlin to Moscow this summer, I would have driven from the city where Hitler died after the defeat of his army in WWII at the hands of the Allies, led in large part by British Prime Minister Winston Churchill, to the city where Stalin died.

Now we need a schematic principle. It is that the following inference is valid.

Had it been that p, it would have been that q

Necessarily, if q then r

Hence

Had it been that p, it would have been that r

That seems right, and so, it seems, is (4).

(4) Necessarily, **if** I drove from the city where Hitler died after the defeat of his army in WWII at the hands of the Allies, led in large part by British Prime Minister Winston Churchill, to the city where Stalin died, **then** Churchill was Prime Minister of Britain during WWII.

And from (3) and (4), (1) follows by the principle. It may take a bit of work to do it, but it seems for any old counterfactual that seems ‘irrelevant’ but turns out to be true on Lewis’s theory we can construct a similar argument.

Posted by Brian Weatherson in *Uncategorized*