David Malament's (1977) well-known result, which is often taken to show the uniqueness of the Poincare-Einstein convention for defining simultaneity, involves an unwarranted physical assumption: that any simultaneity relation must remain invariant under temporal reflections. Once that assumption is removed, his other criteria for defining simultaneity are also satisfied by membership in the same backward (forward) null cone of the family of such cones with vertices on an inertial path. What is then unique about the Poincare-Einstein convention is that it (...) is independent of the choice of inertial path in a given inertial frame, confirming a remark in Einstein 1905. Similarly, what is unique about the backward (forward) null cone definition is that it is independent of the state of motion of an observer at a point on the inertial path. (shrink)

The question whether distant simultaneity has a factual or a conventional status in special relativity has long been disputed and remains in contention even today. At one point it appeared that Malament had settled the issue by proving that the only non-trivial equivalence relation definable from causal connectability is the standard simultaneity relation. Recently, however, Sarkar and Stachel claim to have identified a suspect assumption in the proof by defining a non-standard simultaneity relation from causal connectability. I contend that their (...) critique is based on a misunderstanding of the criteria for the definability of a relation, a misunderstanding that Malement's original treatment helped to foster. There are in fact a variety of notions of definability that can be brought to bear. They all, however, require a condition that suffices to secure Malament's result. The non-standard relation Sarkar and Stachel claim to be definable is not so definable, and, I argue, their proposal to modify the notion of “causal definability” is misguided. Finally, I address the relevance of Malament's result to the thesis of conventionalism. (shrink)

In debate about the nature of persistence over time, the view that material objects endure has played the role of "champion" and the view that they perdure has played the role of the "challenger." It has fallen to the perdurantists rather than the endurantists to motivate their view, to provide reasons for accepting it that override whatever initial presumption there is against it. Perdurantists have sought to discharge their burden in several ways. For example, perdurantism has been recommend on the (...) grounds that: (i) it solves several of the puzzles that raise the problem of material constitution; (ii) it is (at least) suggested by the special theory of relativity (hereafter "SR"); (iii) it is the only view that makes sense out of the possibility of intrinsic change; (iv) it is the only view consistent with the doctrine of Humean supervenience; and (v) it makes better sense than its competitor out of the possibility of fission. There are primary and most powerful claims that have been made on behalf of perdurantism. They are individually persuasive and together they constitute a formidable assault upon the hegemony of endurantism. Endurantists of course, have not been without reply. However, since endurantists typically respond to these claims one at a time and in different ways, it is easy to get the impression that perdurantism offers a single, neat solution to a host of problems whereas endurantism requires a patchwork of different strategies. But this impression is an illusion. In Rea 1995, I argued that though perdurantism does solve some of the puzzles that raise the problem of material constitution, it does not solve the problem of material constitution itself. Thus, the problem of material constitution really has no bearing on the debate between endurantists and perdurantists. In his paper, I will show that the same is true with respect to SR, the problem of intrinsic change, the doctrine of Humean supervenience, and the possibility of fission. In short, I will argue that none of (ii-v) is true and that therefore the doctrine of temporal parts stands unmotivated. (shrink)

Summary A recurrent theme in the philosophical literature on the special theory of relativity is the question as to the reality of the Lorentz contraction. It is often suggested that there is a difference between the Lorentz-FitzGerald contraction in the pre-relativistic ether theory and the Lorentz contraction from special relativity in the sense that the former is a real contraction of matter conditioned by dynamical laws, whereas the latter should be compared with the apparent changes in the size of objects (...) when the perspective of the observer changes. It is here shown, however, that the same laws of nature which are operative in the Lorentz-FitzGerald contraction also condition the relativistic Lorentz contraction. The relevant distinction therefore is not between the reality of the two contractions. What is at issue is the difference in explanatory structure of the pre-relativistic theory on the one hand and the special theory of relativity on the other. In the course of the argument the question of the conventionality of simultaneity is also discussed. (shrink)

Background and assumptions. Persistence and philosophy of time ; Atomism and composition ; Scope ; Some matters of methodology -- Persistence, location, and multilocation in spacetime. Endurance, perdurance, exdurance : some pictures ; More pictures ; Temporal modification and the "problem of temporary intrinsics" ; Persistence, location and multilocation in generic spacetime ; An alternative classification -- Classical and relativistic spacetime. Newtonian spacetime ; Neo-Newtonian (Galilean) spacetime ; Reference frames and coordinate systems ; Galilean transformations in spacetime ; Special relativistic (...) spacetime ; Length contraction and time dilation ; Invariant properties of special relativistic spacetime -- Persisting objects in classical spacetime. Enduring, perduring, and exduring objects in Galilean spacetime ; The argument from vagueness ; From minimal D-fusions to temporal parts ; Motivating a sharp cutoff ; Some objections and replies ; Implications -- Persisting objects in Minkowski spacetime. Enduring, perduring, and exduring objects in Minkowski spacetime ; Flat and curved achronal regions in Minkowski spacetime ; Early reflections on persisting objects in Minkowski spacetime : Quine and Smart ; "Profligate ontology"? ; Is achronal universalism tenable in Minkowski spacetime? ; "Crisscrossing" and immanent causation -- Coexistence in spacetime. The notion of coexistence ; Desiderata ; Coexistence in Galilean spacetime ; Coexistence in Minkowski spacetime : CASH ; Alexandrov-Stein present and Alexandrov-Stein coexistence ; AS-Coexistence v. CASH : symmetry, multigrade, and objectivity ; As-coexistence v. CASH : relevance ; The mixed past of coexistence ; No need in the extended now -- Strange coexistence? Coexistence and existence@ ; The asymmetry thesis ; The absurdity thesis ; Collective CASH value of coexistence ; Collective existence@ and coexistence in classical spacetime ; Collective existence@ and coexistence in Minkowski spacetime ; Contextuality ; Chronological incoherence ; Some objections -- Shapes and other arrangements in Minkowski spacetime. How rigid is a granite block? ; Perspectives in space ; Perspectives in spacetime ; Are shapes intrinsic to objects? ; The causal objection ; The micro-reductive objection ; Pegs, boards, and shapes ; Perduring objects exist. (shrink)

Although considerations based on contemporary space-time theories, such as special and general relativity, seem highly relevant to the debate about persistence, their significance has not been duly appreciated. My goal in this paper is twofold: (1) to reformulate the rival positions in the debate (i.e., endurantism [three-dimensionalism] and perdurantism [four-dimensionalism, the doctrine of temporal parts]) in the framework of special relativistic space-time; and (2) to argue that, when so reformulated, perdurantism exhibits explanatory advantages over endurantism. The argument builds on the (...) fact that four-dimensional entities extended in space as well as time are relativistically invariant in a way three-dimensional entities are not. (shrink)