Mereological nihilism is the metaphysical thesis that composite objects do not exist. Formally, letting P denote the parthood relational predicate:
Pxy ↔ x = y.
When combined with materialism (as is often done), mereological nihilism entails that the only things that exist are physical simples (such as, for example, quarks and electrons). What are taken by common sense to be composite objects (sometimes referred to by philosophers as "common objects") are, according to the mereological nihilist, really nothing but various arrangements of these simples. So, for instance, a chair is nothing but a collection of simples arranged chair-wise. Similarly, a rock is nothing but a collection of simples arranged rock-wise. And so on. The reality of metaphysical substances is denied. With that being said, some forms of mereological nihilism are less radical than others. For example, the metaphysician Peter van Inwagen holds to a restricted form of mereological nihilism that allows for the existence of composite living things (e.g., plants, animals, and humans), while holding everything else to be nothing but arrangements of simples.
In this post, I want to focus on the most extreme form of mereological nihilism: the thesis that there are no composite objects whatsoever, be they living or otherwise. I also will be assuming strict materialism (i.e., to be is to be physical). I shall argue that mereological nihilism thus understood—what we might call strong materialist mereological nihilism—is incompatible with the reality of rationality and valid logical inference.
