es. The new dispositionalist might contend that, while the agent in a Frankfurt case may lack the specific ability to do otherwise, she has the general ability to do otherwise, and that it is this general ability of which the new dispositionalist is giving an account.
This response, however, postpones a crucial and much broader question. The question is this: should ‘ability’ in (PAP) be understood as general ability, or specific ability? If general ability is what matters, then Frankfurt cases may indeed not tell against (PAP), for the agent retains the general ability to do otherwise. If it is specific ability that matters, however, the challenge to (PAP) stands (see also Whittle 2010). This is a vital question for understanding the purported connection between agents’ abilities and questions of moral responsibility, whatever our verdict on new dispositionalism itself. (See Cyr and Swenson 2019 for a helpful recent discussion of these issues).
As noted in Section 1.1, dispositions are simply one member of the broader family of powers, albeit one that has figured prominently in recent metaphysics. An alternative account of abilities might give an account of abilities in terms of some other kind of power, perhaps one better-suited to the distinctive aspects of abilities.
One account of this kind is developed in a series of works by Barbara Vetter (especially Vetter 2015). Vetter proposes that our basic modal notion should be potentiality. On a traditional view (which Vetter rejects) dispositions involve a dyadic relation between a stimulus and a manifestation (for example: a glass is disposed to break when struck). In contrast, potentials involve a monadic relation to a manifestation (for example: a glass has the potential to break). This makes potentials especially well-suited to give an account of abilities, which also appear to involve a monadic relation to an act, namely the act denoted by the complement of an ability-ascription (for example: I am able to play tennis). To have an ability, Vetter argues, is simply to have a certain kind of potentiality. Vetter also provides an explicit semantics for agentive modality in terms of the ascription of potentiality (Vetter 2013), which constitutes a systematic alternative to (MA).
Yet another view is suggested by recent work by Helen Steward emphasizing the traditional idea of a ‘two-way power’ (Steward 2012, Steward 2020; see also Alvarez 2013). Steward argues that actions are exercises of two-way powers — ‘powers which an agent can exercise or not at a given moment, even holding all prior conditions at that moment fixed’ (Steward 2020, 345). These are to be contrasted with one-way powers, which manifest whenever their manifestation conditions are realized, as a fragile glass breaks whenever it is struck. Unlike both the new dispositionalists on the one hand and Vetter on the other, Steward sees a fundamental asymmetry between agents, who are bearers of two-way powers, and mere objects, who are are bearers only of one-way powers. It is natural then to think that what it is to have an ability is to have a two-way power of a certain kind, and that a theory of ability should follow from an account of agency and the two-way powers.
We thus have at least three ‘power-based’ views of abilities: the new dispositionalism, Vetter’s potentiality-based view, and Steward’s two-way power-based view. It is instructive to consider how these three accounts differ with respect to two larger philosophical projects.
One is the project of giving an analysis of modal language, including ability-ascriptions, in terms of possible worlds. The new dispositionalist rejects (CA) and (MA) but she is still, in principle, sympathetic with that project, insofar as she allows that disposition ascriptions themselves may be ultimately understood in terms of quantification over possible worlds. This kind of view is explicitly endorsed, for instance, by Smith (2003). In contrast, Vetter is explicitly opposed to this project, while Steward’s view appears neutral on this question.
Another is the project of arg