Logic and Ontological Pluralism

According to ontological pluralism, there are different modes of being — different ways to exist. The view has been thought dead for a long time, destroyed by the Quinean doctrine that to be is to be needed as the value of a variable bound by an existential quantifier. Announcements of its death were premature. Ontological pluralism is consistent with the Quinean doctrine if there are multiple existential quantifiers. We can have two modes of being — perhaps one for abstracta and another for concreta — and still stay broadly within the Quinean tradition if we also have two quantifiers, say ‘∃a’ and ‘∃c’ for abstracta and concreta, respectively. To be (in the abstract way) is to be needed as the value of a variable bound by ‘∃a’; to be (in the concrete way) is to be needed as the value of a variable bound by ‘∃c’. A defense of this sort of pluralism requires movement on many fronts. In recent work, Kris McDaniel (2009, forthcoming) and I (2010) have developed the view, and defended it against several objections each of which, if correct, would show the view false. But a further objection has yet to be addressed: the objection that, although not false, ontological pluralism fails to be a distinct view from its apparent foe, ontological monism. According to this view, ontological pluralism is a mere notational variant to ontological monism. There is no battle here at all: just one army that can’t agree on what to call itself. I am here to respond to this further objection. More precisely, I will argue that, given a plausible thesis about the relationship between metaphysics and logic, we have good reason to think that ontological pluralism and ontological monism are not notational variants but rather genuine alternatives to each other. In §1, I state more precisely the theory to be defended and the objection it is to be defended from. In §2, I give the basic idea behind the argument. §3 contains a much-needed aside on some details involving the logic(s) of ontological pluralism. §4 provides a technical generalization of §2’s argument, and §5 draws some conclusions from it. ∗This paper grew out of an extended discussion with Jonathan Schaffer. So: Thanks, Jonathan! Thanks also to Robbie Williams and an anonymous referee for valuable suggestions and guidance.