From Possibility to Properties? Or from Properties to Possibility?

This paper contrasts two metaphysical accounts of modality and properties: Modal Realism which treats possible entities as primitive; and Strong Dispositionalism in which metaphysical possibility and necessity are determined by actually existing dispositions or powers. I argue that Strong Dispositionalism loses its initial advantages of simplicity and parsimony over Modal Realism as it is extended and amended to account for metaphysical rather than just causal necessity. Furthermore, to avoid objections to its material and formal adequacy, Strong Dispositionalism requires a richer fundamental ontology which it cannot explicate without appealing either to possible worlds or to an account of counterfactual truth conditions, both of which Strong Dispositionalism was intended to replace.