in Section 4. The more methodological point being made here is that any adequate account of ability ought to provide an account of ability-ascriptions, and as such may want to reckon with this ongoing debate in the semantics of modal expressions.
The bulk of theories of ability that have been defended in the historical and contemporary literature have been what we might call hypothetical theories. On such views, to have an ability is for it to be the case that one would act in certain ways if one were to have certain volitions. One arrives at different theories depending on how one understands the volitions in question and how exactly these actions would hypothetically depend on them, but nonetheless these views constitute something like a unified family. Given their prominence and unity, it is natural to begin our survey of theories of ability with them.
The most prominent hypothetical theory of ability is what has come to be called the ‘conditional analysis’. In this section, we will survey that form of analysis, the problems for it, and alternatives to it that are supposed to overcome those problems.
The conditional analysis of ability has at least two aspects. First, S has an ability to A just in case a certain conditional is true of her. Second, that conditional has the following form: S would A if S were to have a certain volition. The precise form such an analysis will take will depend on, first, how we interpret this conditional and, second, which volition figures in the antecedent.
It has been standard in the literature, when this first question has been raised, to understand the conditional as a subjunctive conditional (Ginet 1980), and we will assume in what follows that this is the best form of the conditional analysis. There has been some disagreement about whether it is a might or a would conditional that is relevant (for an account of this distinction, see Lewis 1973, 21–24), as well as about which volition is relevant. In the following, we will take the relevant conditional to be a would conditional, and the relevant volition to be trying, though nothing will hang on these selections, and the points to be raised would apply also to other forms of conditional analysis, mutatis mutandis.
We thus arrive at the following form of the conditional analysis:
(CA) S has the ability to A iff S would A if S tried to A.
If (CA) were true, it would constitute a theory of ability in that it would say under exactly what conditions some agent has the ability to perform some action without making reference to the idea of ability itself. (Note that a variant on (CA) that is sometimes discussed, according to which S has the ability to A iff S could A if S tried to A, would not meet this standard, since the ‘could’ seems to make a claim about S’s abilities. So such a view is not really a conditional analysis. Indeed, it is not even clear that it involves a genuine conditional, for reasons discussed in Austin 1970 (211–213).
The conditional analysis so understood has been subject to a fair amount of criticism, which will be reviewed in the following section. It bears noting, however, just how apt an account of ability it seems at first pass. It satisfies, at least at first approximation, the extensional constraints: there are many actions with respect to which a typical agent satisfies the relevant conditional, and also many actions with respect to which she does not, and these roughly correspond to her abilities. This imposes a demand even on those who wish to reject (CA), namely to explain why, if (CA) is simply false, it so closely approximates to the truth about abilities.
Its approximate satisfaction of the extensional constraints is also plausibly a reason why something like (CA) has found so many thoughtful advocates. It is at least strongly suggested, for example, by the following remarks from Hume’s Enquiry:
For what is meant by liberty, when applied to voluntary actions? We cannot surely mean that actions have so little connexion with motives, inclinations, and circumstances, that one does not follow with a certain 