 This entry addresses questions framed in terms of modal notions. Are extended simples possible? Is it necessary that nothing is multilocated? All talk of possibility and necessity in what follows should be understood as talk of metaphysical possibility and metaphysical necessity, respectively. In keeping with current orthodoxy, we assume that being metaphysically necessary (a property of propositions or sentences) is not to be identified with being a logical truth, being an analytic truth, being a conceptual truth, or being an a priori truth. Although metaphysical necessity is not identified with conceptual truth—and, correlatively, metaphysical possibility is not identified with conceivability—one might still think that conceivability (or something in that vicinity) is evidence for metaphysical possibility. See Chalmers (2002) for distinctions between various sorts of conceivability and for discussion of how each of them connects or fails to connect to metaphysical possibility. Also see the entry on  the epistemology of modality.