Geometric Possibility, Ideological Parsimony, and Monistic Substantivalism

Monistic substantivalists believe that material objects and regions of space-time are not two distinct kinds of fundamental of entities. For the monist, objects either are identical with regions or are somehow derivative from them. Dualistic substantivalists view regions and objects as distinct kinds of fundamental entities. One virtue monists claim over dualists is that their view is more ideologically parsimonious than dualism because monists can do without a primitive notion of location. In this paper I provide an argument that undercuts some of the theoretical edge that monists claim over dualists. The assumption that the monist can provide a reduction of location unique to her position rests on a false assumption about the possible structures spacetime can have. If it is metaphysically possible for two distinct regions to coincide with respect to all their significant spatiotemporal properties and relations (call these 'coincident regions'), then analyses of location unique to monism will turn out to be inadequate.