2009 Articles

Universalism Entails Extensionalism

Varzi, Achille C.

Universalism (also known as Conjunctivism, or Collectivism) is the thesis that mereological composition is unrestricted. More precisely: Any non-empty collection of things has a fusion, i.e., something that has all those things as parts and has no part that is disjoint from each of them. Extensionalism is the thesis that sameness of composition is sufficient for identity. More precisely: No two things have exactly the same proper parts (unless they are atomic, i.e., have no proper parts at all). Clearly these two theses are not equivalent. They are, however, more closely related than one might think. More precisely, the entailment holds as long as it is agreed that the following postulates are constitutive of the meaning of ‘part’: Transitivity: Any part of any part of a thing is itself part of that thing. Supplementation: Whenever a thing has a proper part, it has at least another part that is disjoint from the first.