ABSTRACT
This chapter suggests that Substantial Priority is in fact a fruitful theory about the mereological structure of composite substances, it is certainly not without its own problems and counterintuitive consequences. It argues that a fundamental mereologoy that ascribes metaphysical primacy to at least some intermediate composite objects if defensible despite recent opinion to the contrary. The chapter starts with the confusion: ordinary material objects do not mereologically overlap their occupying regions, rather, they stand in the primitive occupation relation to them. The phenomena of mereological harmony offers reason to think that material objects not only occupy their regions, but also mereologically overlap their regions in sharing the same compositional structure. The chapter possess candidate diagnostic as to which intermediate objects are metaphysically privileged in terms of the instantiation of certain fundamental or perfectly natural properties, in particular those natural properties that carve out non-redundant causal structure in the world.
