Simon Thunder

There is a widespread intuition that mereology should be ontologically innocent. In this paper, we compare two attempts to deliver this innocence. They both identify a fusion with the plurality of its parts, but they disagree over the logical status of the fusion: according to Composition as Identity (CAI), the fusion is a genuine individual, and in this sense it is both one and many; according to manyism, the fusion is not an individual, and so is merely many. We argue that no version of CAI can make mereology ontologically innocent without violating some independently attractive desiderata. But manyism can. In fact, when the details are appropriately filled out, manyism yields (what we call) mereologicism, the result that all of the axioms of Classical Mereology are logical theorems. Given manyism, mereology is innocent because logic is.

Mereological nihilists typically employ a paraphrase strategy in order to mitigate the apparent absurdity of their denial of the existence of composite objects. I argue here that the nihilist's paraphrase strategy is incomplete, because no schema for generating nihilistically acceptable paraphrases of sentences concerning material constitution has ever been given. Nor can an adequate schema be arrived at by generalising things that nihilists have already said. I fill this lacuna in the nihilist's account by developing and defending a novel paraphrase schema that makes essential reference to the determinable‐determinate relation that holds between arrangement‐properties instantiated by the simples.

I here defend microphysical manyism. According to microphysical manyism, each composite or higher-level object is a mere plurality of microphysical particles. After clarifying the commitments of the view, I offer two physicalist-friendly arguments in its favour. The first argument appeals to the Canberra Plan. Here I argue that microphysical particles acting in unison play the theoretical roles associated with composite objects - that they do everything that we think of composite objects as doing - and thus that composite objects are to be identified with pluralities ofmicrophysical particles. Along the way I rebut the objections that pluralities of particles don’t display the right emergent, ‘lingering’, or modal properties to be good candidates for identification with higher-level objects. In the second argument I claim that microphysical manyism is uniquely able to capture a compelling and widespread physicalist intuition concerning the intimate nature of the relationshipbetween higher-level, composite objects and the microphysical world.

A ubiquitous assumption about composite material objects is that—if they exist at all—they are single things. This chapter articulates and defends manyism, which rejects that assumption. According to manyism, each composite object is simply its many parts. Since manyism accepts the existence of composite objects, it is distinct from nihilism; since manyism denies that composite objects are each one in number in addition to being many in number, it is distinct from the view known as composition as identity (CAI). What’s more, manyism is both coherent and attractive. Manyism is coherent because it can be underwritten by a defensible quasi-Quinean metaontology, and because it’s not analytic that objects are each one in number. Manyism is attractive because it shares all of the benefits of CAI without having to join CAI in objectionably positing many–one identities, and without incurring other serious costs.

In recent times it has become common to encounter philosophers who recommend the replacement of one principle concerning theory choice, Ockham’s Razor, with another: the Laser. Whilst the Razor tells us not to multiply entities beyond necessity, the Laser tells us only to avoid multiplying fundamental entities beyond necessity. There appear to be seven arguments in the literature for the Laser. They divide into three categories: arguments from the nature of non-fundamentality attempt to motivate the Laser by appeal to various observations about what it is to be non-fundamental; arguments from cases describe hypothetical or actual cases, and allege that only the Laser accords with our intuitive judgements about them; and arguments from analogy claim that ontological parsimony is analogous to conceptual economy, and that this analogy recommends the Laser. I provide novel responses to each of the extant arguments for the Laser, and conclude that there is currently no good reason for replacing the Razor with the Laser.

(Mereological) nihilism states that there are no composite objects—there are only sub-atomic particles such as quarks. Nihilism’s biggest rival, (mereological) universalism, posits vast numbers of composite objects in addition to the sub-atomic particles, and so nihilism appears to be the more ontologically parsimonious of the two theories. If this is the case, it’s a significant result for the nihilist: ontological parsimony is almost always thought to be a theoretical virtue, so a nihilist victory in the parsimony stakes gives us a defeasible reason to be nihilists. But things aren’t so straightforward. Karen Bennett (2009) has argued that nihilism is no more quantitatively parsimonious than universalism. Furthermore, her argument can be redirected so that it threatens the nihilist’s perceived advantage over universalism in the qualitative parsimony stakes too. I here argue that these arguments are flawed and that nihilism is indeed more quantitatively and qualitatively parsimonious than universalism.