Ontology of Powers

John Heil

Our conference organizers have posed the question, ‘which ontology does the assumption of irreducible powers suggest or even presuppose?’ In particular we have been asked:

  (1)   How should powers be ontologically categorized? Do they need bearers? If so, to which ontological category might such bearers belong?
  (2)   Does dispositional realism favour an ontology of substances, or events, or tropes, &c?
  (3)   Which account of persistence should dispositionalists endorse?
  (4)   Are there irreducible powers only in the microphysical realm or also in the macrophysical realm?

I accept what I take to be the organizers’ presumption, the idea that ontology is a package deal. An ontology is not something to be constructed by bolting together off-the-shelf parts in the way a hobbyist might assemble a home computer from components purchased at Radio Shack. The components of an ontology owe their integrity to their place in the system.
I sketch an account of powers situated within a substance–property ontology. Substance and property are, as I see it, correlative notions: substances are various ways, properties are ways substances are; every substance is some way or other, every way is a way some substance is. What substances do or would do depends on their properties and properties of substances with which they interact.
Properties, on such a view, are powers, powerful ways substances are. Properties are not purely powers, however: properties are powerful qualities. Properties are qualities the identity of which depends on how they would manifest themselves with particular kinds of reciprocal partner.
A conception of this kind provides sufficient resources to make sense of modality and causation in a decidedly non-Humean manner. Powers can serve as truthmakers for various modal truths. Causation, understood as the mutual manifestation of powers, is revealed to be a kind of internal relation. With this ontological picture in play, it is possible to provide systematic answers to the questions posed above.