Until recently, many have perhaps assumed that metaphysics, or at least that branch of it called ontology, is concerned with issues of existence, and that one's metaphysical position is more or less exhausted by one's position on what entities exist. In his "On What There Is", Quine argued that the ontological commitment of a theory or set of views is determined by what things its quantifiers range over: "To be is to be the value of a variable", as he succinctly put it (Quine 1948: 15). Quine's views were never universal, but the weaker assumption that one's ontological commitments are at the center of one's metaphysics is very widespread. Recently there has been some pushback against this broad Quinean framework. Kit Fine has suggested that "we give up on the account of ontological claims in terms of existential quantification" (Fine 2009: 167). Jonathan Schaffer claims that the Quinean approach has created a "tension in contemporary metaphysics" (Schaffer 2009: 354), one that can only be resolved by returning to a more "Aristotelian" conception of metaphysics. The positive proposals of