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What is a temporal part? Most accounts explain it in terms of timeless parthood: a thing's having a part without temporal qualification. Some find this hard to understand, and thus find the view that persisting things have temporal parts--fourdimensionalism--unintelligible. T. Sider offers to help by defining temporal parthood in terms of a thing's having a part at a time. I argue that no such account can capture the notion of a temporal part that figures in orthodox four-dimensionalism: temporal parts must be timeless parts. This enables us to state four-dimensionalism more clearly.

According to the doctrine of four-dimensionalism, our world and everything in it consists of stages or temporal parts; moreover, where an object exists at various times, it does so, according to the four-dimensionalist, in virtue of having distinct temporal parts at those times. While four-dimensionalism is often motivated by its purported solutions to puzzles about material objects and their persistence through time, it has also been defended by more direct arguments. Three such arguments stand out: (1) the argument from temporary intrinsics, (2) the argument from vagueness and (3) the argument from recombination, Humean supervenience and causal constraints. Not surprisingly, each of these arguments originates in the work of four-dimensionalism’s most prominent modern defender, David Lewis.1 The third of these arguments has received, by far, the least attention, critical or otherwise; it is now time to begin to address this imbalance.

Four-dimensionalism, as I’ll use the term, is the doctrine that reality is spread out in time as well as space.1 Just as objects that are located at multiple regions of space contain parts con ned to those regions of space, so objects that are located at multiple regions of time contain parts — temporal parts — that are con ned to those regions of time. (Or better: an object that occupies an extended spatiotemporal region R has parts con ned to the various subregions of R; but I’ll ignore this complication henceforth.) Most who accept this ontology of perduring objects, as they are often called, identify the continuants of our everyday ontology with “space-time worms” — mereological sums of stages from different times. Elsewhere ( ) I have proposed a different version of four-dimensionalism, which identi es continuants with the stages themselves, and which analyses de re temporal predication with a temporal version of modal counterpart theory (Lewis, , ). On this view, a current assertion of ‘Clinton was indiscreet’ is true iff the (current) referent of ‘Clinton’ — a stage — has an indiscreet temporal counterpart in the past. The temporal counterpart relation is the same “genidentity” or “unity” relation used by the worm theorist to unify the successive stages of continuing space-time worms. In my I supported this view by appeal to its ability to resolve various philosophical puzzles, including the paradoxes of material constitution and Derek Par t’s ( ) puzzle about identity and what matters; the purpose of the present note is to mention one other line of argument. A widely discussed contemporary argument for temporal parts is David Lewis’s argument from temporary intrinsics, according to which only the fourdimensionalist can explain the phenomenon of intrinsic change.2 I am now straight-shaped, but will fail to be straight-shaped in the future. There is an..

How do the familiar concrete objects of common-sense – houses, trees, people, cars and the like – persist through time? According to the position known as ‘four-dimensionalism’ or ‘the doctrine of temporal parts’, ordinary concrete objects persist through time by perduring, i.e., by having temporal parts at all those times at which they exist, in addition to their ordinary spatial parts.1 The contrasting position, known as ‘three-dimensionalism’, holds that ordinary concrete objects lack such an additional temporal dimension; rather, they persist through time by enduring, i.e., by being ‘wholly present’ (whatever exactly that comes to) at each of those times at which they exist.2,3 In his excellent recent 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’: according to this view, ordinary persisting objects are analyzed as being identical to momentary stages; they persist by having temporal counterparts at other times. (The ‘stage-theory’ contrasts with the more familiar ‘worm-theory’, according to which ordinary persisting objects are analyzed as extended space-time worms, rather than momentary stages.) Sider’s claim on behalf of the stagetheory is that it is the position which, on the whole, provides the best analysis of the persistence of ordinary concrete objects: when compared with competing views, the stage-theory yields the best unified solution to a wide range of classical metaphysical puzzles and has “on balance, the most important advantages and the least serious drawbacks” (Sider, 2001, p. 140). Despite all of its many significant virtues, however, Sider’s case for four-dimensionalism is troubling in certain crucial respects, both philosophically and meta-philosophically. My purpose in this paper Philosophical Studies 114: 107–134, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 108..

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.

Some philosophers believe that everyday objects are 4-dimensional spacetime worms, that a person (for example) persists through time by having temporal parts, or stages, at each moment of her existence. None of these stages is identical to the person herself; rather, she is the aggregate of all her temporal parts.1 Others accept “three dimensionalism”, rejecting stages in favor of the notion that persons “endure”, or are “wholly present” throughout their lives.2 I aim to defend an apparently radical third view: not only do I accept person stages; I claim that we are stages.3 Likewise for other objects of our everyday ontology: statues are statue-stages, coins are coin-stages, etc. At one level, I accept the ontology of the worm view. I believe in spacetime worms, since I believe in temporal parts and aggregates of things I believe in. I..

Until recently, perdurantism has been considered to be incompatible with the presentist ontology of time. However, discussions about presentist theories of perdurance are now surfacing, one of the most prominent arguments for which being Berit Brogaard’s essay: “Presentist Four-Dimensionalism”. In this paper, I examine Brogaard’s argument in contrast to Ted Sider’s arguments for (an Eternalist theory of) the “Stage View”. I then argue for another (and, I think, novel) view of presentist perdurantism, which avoids the problematic consequences that Brogaard’s view faces, and which also successfully solves philosophical puzzles without the difficulties that Sider’s view faces. This view, which I call “Stage View Presentism,” thus seems to be an appealing alternative for presentists who remain impartial to both the endurantist and the worm theories of persistence.

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.

Ignoring the temporal dimension, an object such as a railway tunnel or a human body is a three-dimensional whole composed of three-dimensional parts. The four-dimensionalist holds that a physical object exhibiting identity across time—Descartes, for example—is a four-dimensional whole composed of 'briefer' four-dimensional objects, its temporal parts. Peter van Inwagen (1990) has argued that four-dimensionalism cannot be sustained, or at best can be sustained only by a counterpart theorist. We argue that different schemes of individuation of temporal parts are available, which undermines van Inwagen's argument.

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 (Jackson 1998, p. 138). 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!