This paper opposes Universal Mereological Composition. Sider defends it: unless UMC were true, he says, it could be indeterminate how many objects there are in the world. I argue that there is no general connection between how widely composition occurs and how many objects there are in the world. Sider fails to support UMC. Moreover, we should disbelieve in UMC objects. Existing objections against them say that they are radically unlike Aristotelian substances. True, but there is a stronger objection. This is that they are characterized by no properties, and so fail to be like anything—not even themselves.
Elder, Crawford, "Against Universal Mereological Composition" (2008). Philosophy Articles. 10.