ABSTRACT
It is often assumed that any entity or being whatever is trivially one entity, but this can certainly be questioned. Arguably, only an individual of some kind qualifies as one entity or being of that kind, and there are entities that are non-individuals—that is to say, we must include non-individuals in any adequate and comprehensive system of ontology. First of all, some entities are properly regarded as pluralities rather than as individuals, and a plurality is a many rather than a one. Importantly, a plurality of individuals should not be confused with the set of those individuals, such a set just being another (albeit abstract) individual. Second, some entities, such as quantities of matter, qualify neither as individuals nor as pluralities. Such a quantity, then, is neither one nor many: It is not countable but admits of measurement only in respect of its amount (how much, rather than how many). Finally, some entities, including the fundamental “particles” of quantum physics, lack individuality not because they lack countability but because they lack determinate identity. There can, in their case, fail to be a “fact of the matter” as to whether the relation of identity holds between “them”—for instance, between an electron absorbed by an atom and an electron subsequently emitted by that atom. This indeterminacy arises on account of the phenomenon of quantum superposition or entanglement. We can find precedents in Aristotelian metaphysics for some of these distinctions, including that between individual substances and quantities of matter, but others take us beyond anything that can be traced directly to Aristotelian roots.
