I have a roughly formulated and half-baked inquiry:
Suppose that rationality endorses maximizing utility, but there is room for rational supererogation, and so it is sometimes rationally permissible to drink a coffee even if doing so does not maximize utility.
Would you say that there is no decisive reason against drinking the coffee because, although drinking the coffee is rationally inferior to another available option, it is still rationally permissible? Or would you say that, because drinking the coffee is rationally inferior to another available option, there is decisive reason against drinking the coffee even though drinking it is rationally permissible?
I am attracted to a usage of decisive reason according to which the consideration that C pinpoints a decisive reason against A’s X-ing if and only if, because C, A should not X. Given this usage, there is no decisive reason against drinking the coffee (from the point of view of rationality) because, although drinking the coffee is rationally inferior to another available option, drinking the coffee is still rationally permissible and so it is not true that one should not drink the coffee. I wonder if folks would balk at this implication and see usages with this implication as thereby counter-intuitive.
I think that ‘decisive reason’ is pretty much just a technical term. And I think that it tends to be used such that “there is no decisive reason against drinking the coffee because, although drinking the coffee is rationally inferior to another available option, it is still rationally permissible.” The thought would be that if it is rationally permissible to drink the coffee, then there is sufficient reason to drink the coffee, and if there is sufficient reason to drink the coffee, then there isn’t decisive reason against drinking it. So, I would say that you ought to refrain from drinking the coffee, because you have more (or better) reason to do otherwise, but you’re not required to refrain from drinking the coffee.
I don’t find the phrase “A should not X” maximally helpful when we are talking about cases in which there is most reason to not X yet not X-ing is permissible. “A must not X” seems to me clearly to point to the issue of what is permissible rather than what is best but to my ear “A should not X” is ambiguous between the two. Anyway, I don’t know that the history of the usage of “decisive” reasons clearly disambiguated these cases. It might fit with “decisively best” or “decisive with respect to what is permissible”. So I feel like this is a case where stipulation is called for rather than following past practice.
I think you can stipulate it however you’d like, but to my ear “decisive reason against” means it is rationally impermissible.
Super helpful. Thanks so much. Just the sort of feedback I was looking for.