 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).