Abstract

According to one popular criterion of property identity, where X and Y are properties, X is identical with Y if and only if X and Y bestow the same conditional powers on their bearers. In this paper, I argue that this causal criterion of property identity is unsatisfactory, because it fails to provide a sufficient condition for the identification of properties. My argument for this claim is based on the observation that the summing of properties does not entail the summing of the conditional powers that they bestow on an object, but, rather, in some cases their subtraction. If so, the following causal structure seems possible: There are two properties, A and B. Each bestows a different set of conditional powers on its bearer, but the conjunctive property A-and-B bestows exactly the same set of conditional powers as either A or B. If this causal structure is possible, then it creates a serious problem for the causal criterion of property identity