Research Group
in Analytic Philosophy

Abstract

It has been famously argued (Baxter, "Many-One Identity" and Lewis, "Parts of Classes") that any composite object is somehow identical to its parts, a mereological thesis better known as Composition as Identity (CAI). A stronger version of the thesis, which is defended by Baxter but not by Lewis and which is at issue in my paper, claims that any object is *strictly* identical to its parts and, hence, that composition *literally* is identity.  Traditionally, all the attempts to defend strong CAI have been focused on the indiscernibility challenge that results from the fact that an object (one) is identical to its parts (many), which stands out as a blatant failure of Leibniz's Law. However, no one focuses on the ontological dimension of the problem: what does in fact mean, from a specifically ontological point of view, that the parts are the same "portions of reality" -- a term that is as frequent as obscure in the literature on CAI -- as their whole? This paper is aimed at filling this gap: I will thus argue that, if we want to defend strong composition as identity (CAI) -- the thesis that the whole is strictly identical to its parts -- then we have to take the ontological challenge at face value and to abandon a Quinean meta-ontology. In particular, I shall propose a framework for CAI where portions of reality play a pivotal role and which crucially rests on Kit Fine's notion of interpretational modality and on the indefinite extendibility of the domain of quantification.