I'm in the process of reading through Mark Schroeder's latest (fascinating) book, Slaves of the Passions. Therein, he makes the following argument about Brett, who is in a position where he can only satisfy one of two conflicting desires:
". . . there simply can't be a reason for Brett to do everything that promotes his desires. His very situation shows that it is impossible for him to do everything that promotes his desires. So on a generalization of the principle that 'ought' implies 'can', we simply shouldn't accept that there is a reason for Brett to do this." (53)
What I'm curious about here is this generalization of 'ought' implies 'can'. Do we need to think that the generalization holds, that 'has reason' also implies 'can'? I will make a few preliminary remarks about my thoughts so far, and then I'd like to see what people think.
First, a bit about why we might think this is true: Of course, one might think that 'has reason' implies 'can' is just intuitively true (perhaps in the same way that 'ought' implies 'can' is). For a more principled reason, consider the fact that many (including myself) take it that oughts and reasons can be understood in terms of one another, allowing for the following platitudes (my thanks to Christian Coons for mentioning the relevance of the latter): (A) x ought to φ just in case x has most reason to φ; (B) If x has reason to φ then, ceteris paribus, x ought to φ.
If one accepts (A) and (B), it does seem prima facie plausible that having a reason to φ means one can φ. After all, consider a case in which one's only reason were to do some impossible thing. In such a case, one would (it seems) have most reason to do that thing, in which case—by (A)—one ought to do that thing. But then, of course, 'ought' implies 'can' has been violated.
But I find none of this particularly persuasive. First, I do not find the idea that 'has reason' implies 'can' intuitive. It seems to me that if I want to experience what it is like to be a bat, I have some reason to turn into a bat.* Now, of course, it is not possible for me to turn into a bat, and so it will never be the case that I ought to do so, but this doesn't make me think that I have no reason to do so.
But what of the connection to 'ought'? I'm not sure how I feel about this, but let's try it on for size: What if I take the very fact that it is impossible for me to turn into a bat as a very good reason for me not to do so? What's more, I take it that any act's being impossible is going to be a very good reason for me not to perform that act. Then (A) and (B) don't seem to pose a problem any longer. It will never turn out to be the case that my reason to do something impossible is what I have most reason to do (or that all else is really equal) because I will always have a stronger reason not to do it—namely that it is impossible.
Then again, I must admit I'm a bit queasy about the idea that something's being impossible is a reason not to do it. There is something odd about the idea that I take the fact that I can't φ as a consideration against my φ-ing. Then again, there might be other solutions in the same area. Perhaps the impossibility isn't itself a reason against, but there is some other explanation for why it will never turn out that in the balancing of reasons, those to do impossible things rise to the top (or that everything else is ever equal when one has reason to do an impossible thing).
Anyway, I'd like to know what people think. Where do intuitions lie? Is this just an intuitive matter? Or is there some more principled reason to accept 'has reason' implies 'can', perhaps stemming from acceptance of 'ought' implies 'can'?
*Actually, I don't believe this at all, but insofar as I'm playing with this Humean framework, I think it plausible that if desires were connected with reasons in the relevant way, then this desire would mean I had this reason.