The Received View of particles in quantum mechanics is that they are indistinguishable entities within their kinds and that, as a consequence, they are not individuals in the metaphysical sense and self-identity does not meaningfully apply to them. Nevertheless cardinality does apply, in that one can have n> 1 such particles. A number of authors have recently argued that this cluster of claims is internally contradictory: roughly, that having more than one such particle requires that the concepts of distinctness and (...) identity must apply after all. A common thread here is that the notion of identity is too fundamental to forego in any metaphysical account. I argue that this argument fails. I then argue that the failure of individuality and identity applies also to macroscopic physical objects, that the problems cannot be constrained to apply only within the microscopic realm. (shrink)

I introduce a thin concept of ad hoc identity -- distinct from metaphysical accounts of either relative identity or absolute identity -- and an equally thin account of concepts and their content. According to the latter minimalist view of concepts, the content of a concept has behavioral consequences, and so content can be bounded if not determined by appeal to linguistic and psychological evidence. In the case of counting practices, this evidence suggests that the number concept depends on a notion (...) of identity at least as strong as ad hoc identity. In the context of nonrelativistic QM in particular, all of the counting procedures appealed to in the existing literature on nonindividuality are shown to involve ad hoc identity. I then show that Goyal Complementarity and the associated derivation of a strong symmetrization principle in QM can be understood in terms ad hoc identity. Specifically, persistence and non-persistence models of quantum processes are seen to be complementary in the sense that they involve two relations of ad hoc identity that occasionally overlap in empirically meaningful ways. Finally, I attempt to draw out consequences for theories of nonindividuality from the above conceptual analysis. The upshot is that counting and definite cardinality are incompatible with nonindividuality, and that none of the counting procedures cited for quantum phenomena offer positive support for an interpretation in terms of nonindividuals. (shrink)