I argue that Universalism (the thesis that mereological composition is unrestricted) entails Extensionalism (the thesis that sameness of composition is sufficient for identity) as long as the parthood relation is transitive and satisfies the Weak Supplementation principle (to the effect that whenever a thing has a proper part, it has another part disjoint from the first).

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.

Timothy Williamson gives an original and provocative treatment of deep metaphysical questions about existence, contingency, and change, using the latest resources of quantified modal logic. Contrary to the widespread assumption that logic and metaphysics are disjoint, he argues that modal logic provides a structural core for metaphysics.

Until recently, an almost perfect parallelism seemed to hold between theories of identity through time and across possible worlds,as every account in the temporal case(endurantism,perdurantism, exdurantism) was mirrored by a twin account in the modal case (trans-world identity, identity-via-parts, identity-via-counterparts). Nevertheless, in the recent literature, this parallelism has been broken because of the implementation in the debate of the relation of location. In particular, endurantism has been subject to a more in-depth analysis, and different versions of it, corresponding to different (...) ways an entity can be located in time, emerged. In this article, we provide a precise map of the conceptions at stake, complete the debate by introducing a version of endurantism not yet considered in the debate — we call transcendentism — and show that it allows us to provide an effective interpretation of the relation of trans-world identity and an intuitive solution in the temporal case. (shrink)

Four- Dimensionalism defends the thesis that the material world is composed of temporal as well as spatial parts. This defense includes a novel account of persistence over time, new arguments in favour of the four-dimensional ontology, and responses to the challenges four- dimensionalism faces." "Theodore Sider pays particular attention to the philosophy of time, including a strong series of arguments against presentism, the thesis that only the present is real. Arguments offered in favour of four- dimensionalism include novel arguments based (...) on time travel, the debate between spacetime substantivalists and relationalists, and vagueness. Also included is a comprehensive discussion of the paradoxes of coinciding material objects, and a novel resolution of those paradoxes based on temporal counterpart theory. In conclusion Sider replies to prominent objections to four- dimensionalism, including discussion of the problem of the rotating homogenous disk. (shrink)

Thinking about space is thinking about spatial things. The table is on the carpet; hence the carpet is under the table. The vase is in the box; hence the box is not in the vase. But what does it mean for an object to be somewhere? How are objects tied to the space they occupy? This book is concerned with these and other fundamental issues in the philosophy of spatial representation. Our starting point is an analysis of the interplay between (...) mereology (the study of part/whole relations), topology (the study of spatial continuity and compactness), and the theory of spatial location proper. This leads to a unified framework for spatial representation understood quite broadly as a theory of the representation of spatial entities. The framework is then tested against some classical metaphysical questions such as: Are parts essential to their wholes? Is spatial colocation a sufficient criterion of identity? What (if anything) distinguishes material objects from events and other spatial entities? The concluding chapters deal with applications to topics as diverse as the logical analysis of movement and the semantics of maps. (shrink)

Introduction In the first four chapters of this book, I develop and defend a monistic account of human persons according to which human persons are highly ...

Counterfactuals is David Lewis' forceful presentation of and sustained argument for a particular view about propositions which express contrary to fact conditionals, including his famous defense of realism about possible worlds and his theory of laws of nature.

Although the relationship of part to whole is one of the most fundamental there is, this is the first full-length study of this key concept. Showing that mereology, or the formal theory of part and whole, is essential to ontology, Simons surveys and critiques previous theories--especially the standard extensional view--and proposes a new account that encompasses both temporal and modal considerations. Simons's revised theory not only allows him to offer fresh solutions to long-standing problems, but also has far-reaching consequences for (...) our understanding of a host of classical philosophical concepts. (shrink)

The topic of this book is material objects. Like most interesting concepts, the concept of a material object is one without precise boundaries.

In his excellent book, Four-Dimensionalism: An Ontology of Persistence and Time (Sider, 2001), Theodore Sider defends a version of four-dimensionalism which he calls the ‘stage-theory’. This paper focuses on Sider's argument from vagueness and argues that, due to the problematic nature of the argument from vagueness, Sider’s case in favor of four-dimensionalism is in the end not successful.

There is a well-known argument from Leibniz's Law for the view that coincident material things may be distinct. For given that they differ in their properties, then how can they be the same? However, many philosophers have suggested that this apparent difference in properties is the product of a linguistic illusion; there is just one thing out there, but different sorts or guises under which it may be described. I attempt to show that this ‘opacity’ defence has intolerable consequences for (...) the functioning of our language and that the original argument should therefore be allowed to stand. (shrink)

Classical mereology is a formal theory of the part-whole relation, essentially involving a notion of mereological fusion, or sum. There are various different definitions of fusion in the literature, and various axiomatizations for classical mereology. Though the equivalence of the definitions of fusion is provable from axiom sets, the definitions are not logically equivalent, and, hence, are not inter-changeable when laying down the axioms. We examine the relations between the main definitions of fusion and correct some technical errors in prominent (...) discussions of the axiomatization of mereology. We show the equivalence of four different ways to axiomatize classical mereology, using three different notions of fusion. We also clarify the connection between classical mereology and complete Boolean algebra by giving two "neutral" axiom sets which can be supplemented by one or the other of two simple axioms to yield the full theories; one of these uses a notion of "strong complement" that helps explicate the connections between the theories. (shrink)

There is more than one way to say that composition is identity. Yi has distinguished the Weak Composition thesis from the Strong Composition thesis and attributed the former to David Lewis while noting that Lewis associates something like the latter with me. Weak Composition is the thesis that the relation between the parts collectively and their whole is closely analogous to identity. Strong Composition is the thesis that the relation between the parts collectively and their whole is identity. Yi is (...) right that Strong Composition does not fully reflect my view. We must recognize further what, borrowing Lewis's characterization, could be called the "stronger, and stranger" Composition thesis, or what I'll call the Stronger Composition thesis for short. On Strong Composition, it is only collectively that the parts are identical with the whole. On Stronger Composition, they are individually identical with it as well. I will explain and motivate this thesis. (shrink)

Hud Hudson presents an innovative view of the metaphysics of human persons according to which human persons are material objects but not human organisms. In developing his account, he formulates and defends a unique collection of positions on parthood, persistence, vagueness, composition, identity, and various puzzles of material constitution. The author also applies his materialist metaphysics to issues in ethics and in the philosophy of religion. He examines the implications for ethics of his metaphysical views for standard arguments addressing the (...) moral permissibility of our treatment of human persons and their parts, fetuses and infants, the irreversibly comatose, and corpses. He argues that his metaphysics provides the best foundation in the philosophy of religion for the Christian doctrine of the resurrection of the body. Hudson addresses a broad range of metaphysical issues, but among his most strikingly original contributions are his defense of the "Partist" view and his argument for the compatibility of Christianity with a materialistic theory of human persons. (shrink)

According to Peter van Inwagen, visible inanimate objects do not, strictly speaking, exist. In defending this controversial thesis, he offers fresh insights on such topics as personal identity, commonsense belief, existence over time, the phenomenon of vagueness, and the relation between metaphysics and ordinary language.

Precis of my book by this title, for a symposium.

The following quotation, from Frank Jackson, is the beginning of a typical exposition of the debate between those metaphysicians who believe in temporal parts, and those who do not: The dispute between three-dimensionalism and four-dimensionalism, or more precisely, that part of the dispute we will be concerned with, concerns what persistence, and correllatively, what change, comes to. Three-dimensionalism holds that an object exists at a time by being wholly present at that time, and, accordingly, that it persists if it is (...) wholly present at more than one time. For short, it persists by enduring. Four-dimensionalism holds that an object exists at a time by having a temporal part at that time, and it persists if it has distinct temporal parts at more than one time. For short, it persists by perduring. In the light of these comments, some readers will perhaps find the question that forms the title of this paper a little puzzling. They may have learned to use the terms ‘fourdimensionalism’ ‘perdurantism’ and ‘belief in temporal parts’ interchangeably; or perhaps even to define one in terms of the other. Such a usage, however, is inapposite. We might imagine a Flatland-like world of two spatial dimensions and one temporal, whose philosophers are divided between a theory of persistence on which they persist by having temporal parts, and a theory on which they persist by being wholly located in each of several times. This is just the same issue we face, but at least the label ‘four-dimensionalism’ seems inapposite: the four-dimensionalist Flatlanders believe in only three dimensions! (shrink)

Thomas Sattig develops a comprehensive framework for doing philosophy of time, and offers an original three-dimensionalist picture of the material world. He brings together a variety of different perspectives, linking our ordinary conception of time with the physicist's conception, and linking metaphysical questions about time with questions in the philosophy of language.

This paper opposes universal mereological composition (UMC). Sider defends it: unless UMC were true, he says, it could be indeterminate how many objects there are in the world. I argue that there is no general connection between how widely composition occurs and how many objects there are in the world. Sider fails to support UMC. I further argue that we should disbelieve in UMC objects. Existing objections against them say that they are radically unlike Aristotelian substances. True, but there is (...) a stronger objection. This is that they are characterized by no properties, and so fail to be like anything – even themselves. (shrink)

This paper defends Mereological Universalism(the thesis that, for any set S of disjoint objects, there is an object that the members of S compose. Universalism is unpalatable to many philosophers because it entails that if there are such things as my left tennis shoe, W. V. Quine, and the Taj Mahal, then there is another object that those three things compose. This paper presents and criticizes Peter van Inwagen's argument against Universalism and then presents a new argument in favor of (...) Universalism. It turns out that the most reasonable way to resist the argument for Universalism is to deny the existence of artifacts; thus, if we believe in artifacts, we have no real choice other than to embrace Universalism. (shrink)

I focus on three mereological principles: the Extensionality of Parthood (EP), the Uniqueness of Composition (UC), and the Extensionality of Composition (EC). These principles are not equivalent. Nonetheless, they are closely related (and often equated) as they all reflect the basic nominalistic dictum, No difference without a difference maker. And each one of them—individually or collectively—has been challenged on philosophical grounds. In the first part I argue that such challenges do not quite threaten EP insofar as they are either self-defeating (...) or unsupported. In the second part I argue that they hardly undermine the tenability of EC and UC as well. (shrink)

Does a commitment to mereological universalism automatically bring along a commitment to the controversial doctrine of mereological extensionalism—the view that objects with the same proper parts are identical? A recent argument suggests the answer is ‘yes’. This paper attempts a systematic response to the argument, considering nearly every available line of reply. It argues that only one approach—the mutual parts view—can yield a viable mereology where universalism does not entail extensionalism.

Multilocation and Minimal Mereology do not mix well. It has been pointed out that Three-Dimensionalism, which can be construed as multilocation-friendly, runs into trouble with Weak Supplementation. But in fact, regardless of one’s theory of persistence, if someone posits the possibility of any one of several kinds of multilocation, he or she will not be able to maintain the necessity of any of the three axioms of Minimal Mereology: the Transitivity of Proper Parthood, the Asymmetry of Proper Parthood, and Weak (...) Supplementation. In fact, positing even the mere conceivability of cases involving multilocation will require the denial of the analyticity of Minimal Mereology. In response to this, some have claimed that we ought to relativise parthood, either to one region or to two. Unfortunately, if we replace the axioms of Minimal Mereology with region-relativised counterparts, we will not be able to capture the intuitions that supported the original axioms. The only adequate solution, I maintain, is to restrict multilocation to a domain outside the scope of the rules we intuitively take to govern the parthood relation. For those who take Minimal Mereology to be necessary and universal, that will mean relinquishing the possibility of multilocation. (shrink)

I formulate a theory of persistence in the endurantist family and pose a problem for the conjunction of this theory with orthodox versions of special or general relativity. The problem centers around the question: Where are things?

I examine the link between extensionality principles of classical mereology and the anti‐symmetry of parthood. Varzi's most recent defence of extensionality depends crucially on assuming anti‐symmetry. I examine the notions of proper parthood, weak supplementation and non‐well‐foundedness. By rejecting anti‐symmetry, the anti‐extensionalist has a unified, independently grounded response to Varzi's arguments. I give a formal construction of a non‐extensional mereology in which anti‐symmetry fails. If the notion of ‘mereological equivalence’ is made explicit, this non‐anti‐symmetric mereology recaptures all of the structure (...) of classical mereology. (shrink)

The paper addresses various questions about the logical and metaphysical relations between notions of parthood, location and persistence. In particular it argues that the conjunction of mereological extensionalism and multilocation, is highly problematic, if not utterly inconsistent. It thus provides an alternate route to reject multilocation, one that does not rely on Barker and Dowe's well known argument, at least for those who endorse extensionality of parthood. It then argues that other major metaphysical theses such as three-dimensionalism turn out to (...) be at odds with extensionalism. (shrink)

This chapter takes a close look at the thought that mereological relations on material objects mirror, and are mirrored by, parallel mereological relations on their exact locations. This hypothesis is made more precise by means of a battery of principles from which more substantive consequences are derived. Mereological harmony turns out to entail, for example, that atomistic space is an inhospitable environment for material gunk or that Whiteheadian space is not a hospitable environment for unextended material atoms.

This paper defends Mereological Universalism (the thesis that, for any set S of disjoint objects, there is an object that the members of S compose. Universalism is unpalatable to many philosophers because it entails that if there are such things as my left tennis shoe, W. V. Quine, and the Taj Mahal, then there is another object that those three things compose. This paper presents and criticizes Peter van Inwagen’s argument against Universalism and then presents a new argument in favor (...) of Universalism. It turns out that the most reasonable way to resist the argument for Universalism is to deny the existence of artifacts; thus, if we believe in artifacts, we have no real choice other than to embrace Universalism. (shrink)

In a recent article in this journal, Achille Varzi (2009) argues that mereological universalism (U) entails mereological extensionalism (E). The thesis that U entails E (call it ‘T’) has important implications. For example, as is well known, T plays a crucial role in Peter van Inwagen’s argument against universalism (1990: 74–79). In what follows, I show that Varzi’s arguments for T rely on a tendentious assumption about parthood.

The paper provides a new and detailed critique of Barker and Dowe’s argument against multi-location. This critique is not only novel but also less committal than previous ones in the literature in that it does not require hefty metaphysical assumptions. The paper also provides an analysis of some metaphysical relations between mereological and locational principles.

This paper opposes universal mereological composition. Sider defends it: unless UMC were true, he says, it could be indeterminate how many objects there are in the world. I argue that there is no general connection between how widely composition occurs and how many objects there are in the world. Sider fails to support UMC. I further argue that we should disbelieve in UMC objects. Existing objections against them say that they are radically unlike Aristotelian substances. True, but there is a (...) stronger objection. This is that they are characterized by no properties, and so fail to be like anything – even themselves. (shrink)