The question of whether there could be a physical object that is necessarily constantly active has a long history, and it has recently arisen again in the literature on dispositions. I examine and critique two proposals for affirming the possibility of such an object. I then advocate a third option, one which is workable if paired with natural-kind essentialism. Finally I briefly outline three possible implications of this view for wider debates concerning the ontology of dispositions and natural kinds.

Marc Lange and Ann Whittle have independently developed an important challenge to dispositionalism, arguing that dispositions are reducible to primitive subjunctive facts. I argue in reply that by pairing dispositionalism with a certain version of natural-kind essentialism, their objection can be overcome. Moreover, such a marriage carries further advantages for the dispositionalist. My aim is therefore two-fold: to defend dispositionalism, and to give the dispositionalist some new motivation to adopt natural-kind essentialism.

Talk of powers is muddled. Building upon Powers and capacities in philosophy: The new aristotelianism, Routledge, London, 2012a, pp 207–227), I disambiguate four senses of the term: powers construed as activity, as capacity/potentiality, as essence and as necessity, respectively, in an attempt to clarify what it is that realists about causal powers take themselves to be realists about.

I argue that realism about causal powers sublates the passivist, Humean-inflected free will problematic. In the first part of the paper I show that adopting what I call ‘powers-non-determinism’ reconfigures the conceptual terrain with respect to the causation component of the contemporary problematic. In part two I show how adopting ‘powers-non-determinism’ significantly alters the nature of the discussion with respect to the agency component of the problematic. In part three I compare ‘powers-non-determinism’ to an otherwise- Humean agent causal position.

Dispositional essentialists ultimately appeal to dispositional essences in order to provide (a) an explanation of the conservation of physical quantities and (b) identity conditions for fundamental physical properties. This paper aims to offer alternative suggestions based on symmetry considerations and exhibits their consequences for the thesis of dispositional essentialism.