A strange kind of power: Vetter on the formal adequacy of dispositionalism

According to dispositionalism about modality, a proposition is possible just in case something has, or some things have, a power or disposition for its truth; and is necessary just in case nothing has a power for its falsity. But are there enough powers to go around? In Yates (2015) I argued that in the case of mathematical truths such as , nothing has the power to bring about their falsity or their truth, which means they come out both necessary and not possible. Combining this with axiom (T): p⊃◇p, it is easy to derive a contradiction. I suggested that dispositionalists ought to retreat a little and say that is possible just in case either p, or there is a power to bring it about that p, grounding the possibility of mathematical propositions in their truth rather than in powers. Vetter’s (2015) has the resources to provide a response to my argument, and in her (2018) she explicitly addresses it by arguing for a plenitude of powers, based on the idea that dispositions come in degrees, with necessary properties a limiting case of dispositionality. On this view there is a power for , without there being a power to bring about its truth. In this paper I argue that Vetter’s case for plenitude does not work. However, I suggest, if we are prepared to accept metaphysical causation, a case can be made that there is indeed a power for .