 Though MacDonald and MacDonald (1986) don’t officially offer an account of determination, they were the first to see determination as useful for addressing the threat of causal overdetermination. Effectively, they suggest that the relation between mental and physical properties is analogous to determination: in both cases the properties at issue are, they maintain, type-distinct but token-identical, thus avoiding problematic overdetermination while preserving type-level causal relevance. Here and elsewhere, token-identity accounts of determinables and determinates do not clearly accommodate certain of the (e.g., perceptual) motivations for irreducible determinables; token-identity accounts are also subject to an extension of Horgan’s (1989) concerns with reductive accounts of mental states, according to which, insofar as the causal relata are ultimately located particulars (events, objects, property instances), the efficacy of determinables qua determinable—that is, qua distinctively unspecific—requires that determinable and determinate tokens as well as types be distinct.