Is Weak Supplementation analytic?

Synthese https://doi.org/10.1007/s11229-018-02066-9 S.I.: MEREOLOGY AND IDENTITY Is Weak Supplementation analytic? A. J. Cotnoir1 Received: 31 May 2018 / Accepted: 12 December 2018 © The Author(s) 2018 Abstract Mereological principles are often controversial; perhaps the most stark contrast is between those who claim that Weak Supplementation is analytic—constitutive of our notion of proper parthood—and those who argue that the principle is simply false, and subject to many counterexamples. The aim of this paper is to diagnose the source of this dispute. I’ll suggest that the dispute has arisen by participants failing to be sensitive to two different conceptions of proper parthood: the outstripping conception and the non-identity conception. I’ll argue that the outstripping conception (together with a specific set of definitions for other mereological notions), can deliver the analyticity of Weak Supplementation on at least one sense of ‘analyticity’. I’ll also suggest that the non-identity conception cannot do so independently of considerations to do with mereological extensionality. Keywords Mereology · Identity · Parthood · Supplementation · Analyticity · Extensionality Philosophy can be strange—perhaps metaphysics especially so. But the dispute over Weak Supplementation is particularly odd. Weak Supplementation is an intuitive mereological decomposition principle governing proper parthood; it is frequently used in the philosophical literature on mereology. The disputants on the one hand seem to think that the principle is so natural that it is analytic; the very meaning of ‘proper parthood’ guarantees its truth. On the other hand, many metaphysicians (both past and present) have argued that Weak Supplementation is false, or endorsed metaphysical theories in clear violation of it, and have supplied an ever-growing list of potential counterexamples. This is strange, since, the dispute over the axiom appears meaningful and substantive; those involved seem semantically competent and don’t appear to be talking past one another. B A. J. Cotnoir http://www.st-andrews.ac.uk/∼ac117 1 University of St Andrews, Edgecliffe G07, The Scores, St Andrews, Fife KY16 9AL, UK 123 Synthese The aim of this paper is to diagnose the source of the dispute. In Sect. 1, I’ll outline the main lines of the controversy, giving a run-down of most of the types of counterexamples to Weak Supplementation that have been put forward. In Sect. 2, I’ll suggest that the dispute has arisen by participants failing to be sensitive to two different conceptions of proper parthood—the outstripping conception and the non-identity conception. In Sect. 3, I’ll examine a number of different notions of analyticity and I’ll argue that, given the outstripping conception together with a specific set of definitions for other mereological notions, there’s at least one sense of ‘analyticity’ in which Weak Supplementation is indeed analytic. Finally, I’ll suggest that the analyticity of Weak Supplementation on the non-identity conception is deeply entangled with mereological extensionality. 1 The controversy I’ll use P for the parthood predicate, P P for proper parthood, and O for mereological overlap. How we should understand these notions, and how precisely they should be formally defined, is part of what is at issue in the debate. But to fix ideas, we can think of parthood P as a form of parthood compatible with identity as a limiting case, and mereological overlap O as the relation that holds when things have parts in common. The Weak Supplementation principle (WSP), can be stated as follows: Weak Supplementation ∀x∀y(P P x y → ∃z(Pzy ∧ ¬Ozx)) WSP states that whenever an object has a proper part, it has another part that does not overlap—that is mereologically disjoint—from the first. This is a straightforward statement of a basic decomposition intuition, the idea that when a proper part is ‘removed’ from a whole, there must be another ‘supplementing’ disjoint proper part. (This, of course, entails that no composite object can have exactly one proper part.) Many philosophers have been struck by how natural Weak Supplementation seems, and have suggested that the principle analytically true, that it is partly constitutive of the notion of proper parthood. For example, Varzi (2008, p. 110) claims ‘This principle expresses a minimal requirement which any relation must satisfy (besides reflexivity, antisymmetry and transitivity) if it is to qualify as parthood at all.’ Simons (1987, p. 116) claims that ‘[Weak Supplementation] is indeed analytic—constitutive of the meaning of proper part’.1 A growing number of metaphysicians have challenged the axiom and endorsed mereologies without Weak Supplementation. It is not difficult to conceive of mereological scenarios that appear to violate WSP. For instance, whoever thinks that a statue and the corresponding lump of clay are part of each other will find WSP unreasonable.2 After all, such parts are coextensive; why should we expect anything to be left over when, say, the clay is ‘subtracted’ from the statue (Donnelly 2011, p. 230)? 1 Similar attitudes toward supplementation principles are expressed in Oppy (2006, pp. 213–215), Effin- gham and Robson (2007, p. 635), Koslicki (2008, pp. 167–168), Bohn (2009, p. 27 footnote 3), Mcdaniel (2009, p. 264), Bynoe (2010, p. 93). 2 E.g. Thomson (1983, 1998), Cotnoir (2010, 2016). See also Sider (2001, p. 155). 123 Synthese Cotnoir and Bacon (2012) note that Weak Supplementation is inconsistent with the possibility of proper parthood loops. This is, in part, because WSP entails the irreflexivity of P P in any system where P P is transitive. Suppose P P x x. Then by WSP there must be some z such that Pzx and ¬Ozx, which is impossible. So any purported counterexample to irreflexivity of proper parthood—any self-part—will be thereby serve as a counterexample to Weak Supplementation. The growing literature surrounding the topic of mereology and time travel has delivered just such examples.3 Effingham offers the following scenario. Imagine a cube, with each side measuring 10m, made of a homogeneous substance. [...] Not only do we take it back to a time that it previously existed at, but we use a shrinking machine and miniaturize by a factor of 100. We then remove a cube-shaped portion, with edges measuring 10cm, from the earlier, larger version of the cube and replace that portion with the miniaturized future version (which now fits perfectly). The cube is now a proper part of itself at that time. (Effingham 2010, p. 335) Kearns (2011) has argued against irreflexivity, pointing out that if structured propositions are constructed mereologically, then e.g. the following proposition would appear to be a self-part.4 ( p) Proposition p is abstract. For different case, also due to Kearns (2011), self-similar shapes such as fractals might be said to contain themselves as parts in a sense other shapes do not. Indeed, the same could be (...truncated)