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.

Persistence through time is like extension through space. A road has spatial parts in the subregions of the region of space it occupies; likewise, an object that exists in time has temporal parts in the various subregions of the total region of time it occupies. This view — known variously as four dimensionalism, the doctrine of temporal parts, and the theory that objects “perdure” — is opposed to “three dimensionalism”, the doctrine that things “endure”, or are “wholly present”.1 I will (...) attempt to resolve this dispute in favor of four dimensionalism by means of a novel argument based on considerations of vagueness. But before argument in this area can be productive, I believe we must become much clearer than is customary about exactly what the dispute is, for the usual ways of formulating the dispute are flawed, especially where three dimensionalism is concerned. (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)

In this book, Lawrence Sklar demonstrates the interdependence of science and philosophy by examining a number of crucial problems on the nature of space and ...

A formal theory of quantity T Q is presented which is realist, Platonist, and syntactically second-order (while logically elementary), in contrast with the existing formal theories of quantity developed within the theory of measurement, which are empiricist, nominalist, and syntactically first-order (while logically non-elementary). T Q is shown to be formally and empirically adequate as a theory of quantity, and is argued to be scientifically superior to the existing first-order theories of quantity in that it does not depend upon empirically (...) unsupported assumptions concerning existence of physical objects (e.g. that any two actual objects have an actual sum). The theory T Q supports and illustrates a form of naturalistic Platonism, for which claims concerning the existence and properties of universals form part of natural science, and the distinction between accidental generalizations and laws of nature has a basis in the second-order structure of the world. (shrink)

This paper is concerned with the debate between substantival and relational theories of space-time, and discusses two difficulties that beset the relationalist: a difficulty posed by field theories, and another difficulty called the problem of quantities. A main purpose of the paper is to argue that possibility can not always be used as a surrogate of ontology, and that in particular that there is no hope of using possibility to solve the problem of quantities.

In this chapter, I evaluate various conceptions of distance. Of the two most prominent, one takes distance relations to be intrinsic, the other extrinsic. I recommend pluralism: different conceptions can peacefully coexist as long as each holds sway over a distinct region of logical space. But when one asks which conception holds sway at the actual world, one conception stands out. It is the conception of distance embodied in differential geometry, what I call the Gaussian conception. On this conception, all (...) fundamental facts about distance are “local” facts.” But there is a problem: the Gaussian conception, notwithstanding its mathematical and physical credentials, appears metaphysically suspicious on Humean grounds. In the final section, I suggest that the Gaussian conception can be given a sound metaphysical footing in terms of non-standard analysis. (shrink)

This is a defense of endurantism against an alleged paradox.

I will discuss only one of the several entwined strands of the philosophy of space and time, the question of the relation between the nature of motion and the geometrical structure of the world.1 This topic has many of the virtues of the best philosophy of science. It is of long-standing philosophical interest and has a rich history of connections to problems of physics. It has loomed large in discussions of space and time among contemporary philosophers of science. Furthermore, there (...) is, I think, widespread agreement that recent insights here have lead to a genuine deepening of our understanding. (shrink)

After Leibniz's death in 1716, Clarke published an edition of their philosophical correspondence--a wide-ranging discussion of the nature of God, human souls, free will and indifference of choice, space and time, the vacuum, miracles, and matter and force. Clarke included his own letters, his translations of Leibniz's letters, and some translated passages from Leibniz's French and Latin works that helped to illuminate their exchanges.

Part One of my dissertation is about composite objects: things with proper parts, like plates, planets, plants and people. I begin chapter 1 by pointing out that if one were to judge by the way we normally speak about composite objects, one would suppose that we were all completely certain of a theory I call folk mereology. For instance, we seem to be completely convinced that whenever some things are piled up, there is an object---a pile---which they compose. I point (...) out that folk mereology is neither an analytic truth nor a theory for which we have conclusive empirical evidence. So what are we to make of the feeling that it makes no sense to deny folk mereology? What this shows, I claim, is that the standard which an assertion about composite objects has to meet in order to be correct is not strict and literal truth, but something less demanding. ;In the last part of chapter 1 and in chapter 2, I argue that we have no evidence for the existence of composite objects, and that without such evidence we ought to believe that there aren't any composite objects. Chapter 3 is devoted to working out some details of a broadly "fictionalist" explanation of the fact that claims about composite objects can be correct without being strictly and literally true. ;In Part Two I defend a parallel view about complex attributes---properties, relations and propositions. In our ordinary talk about attributes, we seem to presuppose a theory according to which there are very many of these entities; but, as I argue in chapter 4, we cannot justifiably be certain that this theory is true. I conclude that in this case too, correct assertion diverges from strict and literal truth. Chapter 5 is devoted to an argument that there are in fact no complex attributes. Finally, in chapter 6, I develop a fictionalist account of the conditions under which ordinary assertions about attributes are correct. (shrink)

I thank my commentators for their kind words, and for their close reading and challenging criticisms of my book. I have chosen selective and substantive replies. Those criticisms I ignore, I ignore because I have little more to say, not because they are unworthy of discussion.