 It should be emphasized that these ways of delimiting metaphysics do not presuppose that all of the topics we've considered as examples of metaphysics are substantive or important to the subject. Consider the debate about modality. Quine (1953) and Sider (2012) both argue from their respective theories about the nature of metaphysics that aspects of the debate over the correct metaphysical theory of modality are misguided. Others are skeptical of the debates about composition or persistence through time. So theories about the nature of metaphysics might give us new resources for criticizing particular first-order debates that have historically been considered metaphysical, and it is common practice for metaphysicians to regard some debates as substantive while adopting a deflationist attitude about others.