It seems obvious that I could have failed to exist. My parents could easily never have met, in which case I should never have been conceived and born. The like applies to everyone. More generally, it seems plausible that whatever exists in space and time could have failed to exist. Events could have taken an utterly different course. Our existence, like most other aspects of our lives, appears frighteningly contingent. It is therefore surprising that there is a proof of my (...) necessary existence, a proof that generalizes to everything whatsoever. I will explain the proof and discuss what to make of it. A first reaction is that a ‘proof’ of such an outrageous conclusion must contain some dreadful fallacy. Yet the proof does not collapse under scrutiny. Further reflection suggests that, suitably interpreted, it may be sound. So interpreted, the conclusion is not outrageous, although it may not be the view you first thought of. (shrink)

(No abstract is available for this citation).

According to the indispensability argument, the fact that we quantify over numbers, sets and functions in our best scientific theories gives us reason for believing that such objects exist. I examine a strategy to dispense with such quantification by simply replacing any given platonistic theory by the set of sentences in the nominalist vocabulary it logically entails. I argue that, as a strategy, this response fails: for there is no guarantee that the nominalist world that go beyond the set of (...) sentences in the nominalist language such theories entail. However, I argue that what such theories show is that mathematics can enable us to express possibilities about the concrete world that may not be expressible in nominalistically acceptable language. While I grant that this may make quantification over abstracta indispensable, I deny that such indispensability is a reason for accepting them into our ontology. I urge that the nominalist should be allowed to quantify over abstracta whilst denying their existence and I explain how this apparently contradictory practice (a practice I call 'weaseling') is in fact coherent, unproblematic and rational. Finally, I examine the view that platonistic theories are simpler or more attractive than their nominalistic reformulations, and thus that abstract ought to be accepted into our ontology for the same sorts of reasons as other theoretical objects. I argue that, at least in the case of numbers, functions and sets, such arguments misunderstand the kind of simplicity and attractiveness we seek. (shrink)

1. IntroductionA popular view in metaphysics is that which propositions are true depends upon how the world is . In more evocative language, truth requires ground. This thought then gets used to do some serious work. As Sider has it, ‘[t]he point of … the principle that truth supervenes on being is to rule out dubious ontologies’. Here, I argue that ‘dubious’ ontologies are theoretically virtuous.

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)