This book is a defense of modal realism; the thesis that our world is but one of a plurality of worlds, and that the individuals that inhabit our world are only a few out of all the inhabitants of all the worlds. Lewis argues that the philosophical utility of modal realism is a good reason for believing that it is true.

Those who accept the necessity of mereological universalism face what has come to be known as the ‘junk argument’ due to Bohn [2009], which proceeds from the incompatibility of junk with universalism and the possibility of junk, to conclude that mereological universalism isn't metaphysically necessary. Most attention has focused on ; however, recent authors have cast doubt on . This paper undertakes a defence of premise against three main objections. The first is a new objection to the effect that Bohn's (...) defence of that premise presupposes far too much. I show that one can defend premise from a much weaker set of assumptions. The second objection, due to Contessa [2012], is that those who accept unrestricted composition should only accept the existence of binary sums rather than infinitary fusions. I argue that this conception of unrestricted composition is problematic: it is in conflict with an intuitive remainder principle. The final objection is .. (shrink)

(No abstract is available for this citation).

(No abstract is available for this citation).

According to standard, pre-philosophical intuitions, there are many composite objects in the physical universe. There is, for example, my bicycle, which is composed of various parts - wheels, handlebars, molecules, atoms, etc. Recently, a growing body of philosophical literature has concerned itself with questions about the nature of composition.1 The main question that has been raised about composition is, roughly, this: Under what circumstances do some things compose, or add up to, or form, a single object? It turns out that (...) it is surprisingly difficult to give a satisfactory answer to this question that accords with standard, pre-philosophical intuitions about the universe's composite objects. In fact, the three rival views in response to this question that have received the most support in the literature are (i) that there are no objects composed of two or more parts (which means that there are no stars, chairs, humans, or bicycles);2 (ii) that the only objects composed of two or more parts are living organisms (which still means no stars. (shrink)

Let’s begin with a simple example. Consider two quarks: one near the tip of your nose, the other near the center of Alpha Centauri. Here is a question about these two subatomic particles: Is there an object that has these two quarks as its parts and that has no other parts? According to one view of the matter (a view that is surprisingly endorsed by a great many contemporary philosophers), the answer to this question is Yes. But I think it (...) is fair to say that according to common sense, the answer to this question is really No, there is no object that has as its only two parts a quark near the tip of your nose and another quark near the center of Alpha Centauri. (shrink)

I first explore the notion of the world's being such that everything in it is a proper part. I then explore the notion of the world's being such that everything in it both is and has a proper part. Given two well recognized assumptions, I argue that both notions represent genuine metaphysical possibilities. Finally I consider, but dismiss, some possible objections.

‘‘Thus I believe that there is no part of matter which is not—I do not say divisible—but actually divided; and consequently the least particle ought to be considered as a world full of an infinity of different creatures.’’ (Leibniz, letter to Foucher).

A mereological structure is junky if and only if each of its elements is a proper part of some other. The young literature on junk has focused on junky worlds and whether they are counterexamples to unrestricted composition. The present note defends the possibility of junky structures that are not worlds. This possibility complicates a recent attempt in the literature to render junk consistent with a weakened form of unrestricted composition. The upshot is that junky non-worlds threaten the weakened form (...) of unrestricted composition as much as junky worlds threaten the traditional version. (shrink)

In this paper I argue that we need to take irreducibly plural logic more seriously in metaphysical debates due to the fact that the verdict of many metaphysical debates hangs on it. I give two examples. The main example I focus on is the debate recently revived by Jonathan Schaffer over the fundamental cardinality of the world. I show how the three main arguments provided by Schaffer are unsound in virtue of an employment of plural logic. The second example I (...) give is a more general issue about the possibility of emergent properties of mereological wholes. Employing plural logic there is a new way to understand such cases. The upshot is that plural logic greatly matters to metaphysics and hence can no longer be ignored the way it has in this area. (shrink)

Many metaphysicians accept the view that, necessarily, any collection of things composes some further thing. Necessarily, my arms, legs, head, and torso compose my body; necessarily, my arms, my heart, and the table compose something y; necessarily, my heart and the sun compose something z; and so on. 1 Though there have been a few recent attempts to argue against the necessity of this principle of unrestricted composition the consensus is that if it is true, it is necessarily true. 2In (...) what follows I will join the few dissenters and argue that this principle of unrestricted composition is not necessarily true. If I am right, it follows that either some principle of restricted composition is necessarily true or the existence of composite objects is a contingent matter. I will end by indicating why the latter option seems the most plausible. 3I proceed by reductio. Assume the following: Unrestricted composition is necessarily true.That is, assume that necessarily, any collection of things composes something. Then, necessarily, the collection of everything composes something. That is, necessarily, there exists a universal object U having all things as parts, not itself being a proper part of anything. Hence, by our assumption, we get: There must be a universal object U.It is important to note that this is so whether the world is finite or infinite. Holding that in worlds of finite cardinality there is a universal object U while in worlds of infinite cardinality there is no universal object U amounts to accepting a restricted form of composition. 4Now consider the following scenario. Everything in this world is spatially extended and just one half of something else that is also spatially extended. That is, for any thing in this world, there is something else of which …. (shrink)

There is widespread disagreement as to what the facts are concerning just when a collection of objects composes some further object; but there is widespread agreement that, whatever those facts are, they are necessary. I am unhappy to simply assume this, and in this paper I ask whether there is reason to think that the facts concerning composition hold necessarily. I consider various reasons to think so, but find fault with each of them. I examine the theory of composition as (...) identity, but argue that the version of this doctrine that entails universalism is implausible. I consider the claim that the a priority of such facts leads to their necessity, but give a defence of substantial contingent a priori truths. I ask whether the contingency of such facts would lead to unwelcome possibilities, but argue that the worrying looking possibilities can be blocked if it is desired. Next, I argue against the thought that the Lewis-Sider argument against restricted composition might give us reason to accept the necessity of universalism. Lastly, I respond to two objections from the 2006 BSPC. I conclude in favour of the contingency of the facts concerning when some things compose some thing. (shrink)