Recent philosophy of science has been seized by what may appear a schizophrenic attitude towards analytic metaphysics. Some philosophers of science have embraced metaphysical theorizing as an important tool for interpreting and extending scientific theories, while others reject analytic metaphysics as misguided, futile, or epistemically impotent. The idea of naturalized metaphysics—metaphysics appropriately ‘grounded’ in the details of empirical science—offers one possibility of a rapprochement between these seemingly conflicting attitudes. In this chapter, however, it is argued that the crucial notion of ‘grounding’, and hence the idea of naturalized metaphysics itself, have not yet been articulated in a compelling manner. The beginnings of an articulation are sketched.