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

How do things persist? Are material objects spread out through time just as they are spread out through space? Or is temporal persistence quite different from spatial extension? This key question lies at the heart of any metaphysical exploration of the material world, and it plays a crucial part in debates about personal identity and survival. This book explores and compares three theories of persistence — endurance, perdurance, and stage theories — investigating the ways in which they attempt to account (...) for the world around us. Having provided valuable clarification of its two main rivals, the book concludes by advocating stage theory. Such a basic issue about the nature of the physical world naturally has close ties with other central philosophical problems. This book includes discussions of change and parthood, of how we refer to material objects at different times, of the doctrine of Humean supervenience, and of the modal features of material things. In particular, it contains new accounts of the nature of worldly vagueness, and of what binds material things together over time, distinguishing the career of a natural object from an arbitrary sequence of events. Each chapter concludes with a reflection about the impact of these metaphysical debates upon questions about our personal identity and survival. (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)

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)

In his interesting article 'Constitution is not Identity' (1992), Mark Johnston argues that (in a sense soon to be explained) constitution is distinct from identity. In what follows, I dispute Johnston's contention.

It seems evident that things sometimes get bigger by acquiring new parts. But there is an ancient argument purporting to show that this is impossible: the paradox of increase or growing argument.i Here is a sketch of the paradox. Suppose we have an object, A, and we want to make it bigger by adding a part, B. That is, we want to bring it about that A first lacks and then has B as a part. Imagine, then, that we conjoin (...) B to A in some appropriate way. Never mind what A and B are, or what this conjoining amounts to: let A be anything that can gain a part if anything can gain a part, and let B be the sort of thing that can become a part of A, and suppose we do whatever it would take to make B come to be a part of A if this is possible at all. Have we thereby made B a part of A? It seems not. We seem only to have brought it about that B is attached to A, like this. (shrink)

Among theories which fit all of our data, we prefer the simpler over the more complex. Why? Surely not merely for practical convenience or aesthetic pleasure. But how could we be justified in this preference without knowing in advance that the world is more likely to be simple than complex? And isn’t this a rather extravagant a priori assumption to make? I want to suggest some steps we can take toward reducing this embarrassment, by showing that the assumption which supports (...) favouring simplicity is far more modest than it first seems. (shrink)

This paper defends the view of continuants as 'four-dimensional worms' against an argument of Geach's. This is to the effect that if continuants are four-dimensional worms then their stages either do, or do not, fall under the very general terms satisfied by the continuants themselves (a stage of a man either is, or is not, a man); but that either alternative is untenable. I try to show how the former alternative may be defended by appealing to some of Geach's own (...) ideas about identity; then go on to defend the four-dimensionalist view from a criticism of it by Mellor, and finish with an account of the intuitive distinction between process and continuant terms. (shrink)