On the Existence of Spacetime Structure

Abstract

I examine the debate between substantivalists and relationalists about the ontological character of spacetime and conclude it is not well posed. I argue that the so-called Hole Argument does not bear on the debate, because it provides no clear criterion to distinguish the positions. I propose two such precise criteria and construct separate arguments based on each to yield contrary conclusions, one supportive of something like relationalism and the other of something like substantivalism. The lesson is that one must fix an investigative context in order to make such criteria precise, but different investigative contexts yield inconsistent results. I examine questions of existence about spacetime structures other than the spacetime manifold itself to argue that it is more fruitful to focus on pragmatic issues of physicality, a notion that lends itself to several different explications, all of philosophical interest, none privileged a priori over any of the others. I conclude by suggesting an extension of the lessons of my arguments to the broader debate between realists and instrumentalists. † This paper is forthcoming in British Journal for Philosophy of Science, 2015. ‡ I owe a great debt to Howard Stein's papers "Yes, but. . . : Some Skeptical Remarks on Realism and Anti-Realism" and "Some Reflections on the Structure of Our Knowledge in Physics", both of which inspired the paper's spirit. I am not sure whether Prof. Stein would endorse the paper's methods. I have hopes he would. It is a pleasure to thank the Philosophy Department at Carnegie Mellon for tough questioning after a colloquium in which I presented an earlier version of this paper, and in particular Richard Scheines, Teddy Seidenfeld and Peter Spirtes for pushing me on the arguments of §3; I thank as well the philosophy of physics reading group at Irvine, and especially Jim Weatherall, for penetrating questions about §3. The paper is much stronger for my attempts to address their skepticism. I also thank the Fellows at the Center for Philosophy of Science (2008Science ( -2009 [W]e must bear in mind that the scientific or science-producing value of the efforts made to answer these old standing questions is not to be measured by the prospect they afford us of ultimately obtaining a solution, but by their effect in stimulating men to a thorough investigation of nature. To propose a scientific question presupposes scientific knowledge, and the questions which exercise men's minds in the present state of science may very likely be such that a little more knowledge would shew us that no answer is possible. The scientific value of the question, How do bodies act on one another at a distance?is to be found in the stimulus it has given to investigations into the properties of the intervening medium. James Clerk Maxwell "Attraction", Encyclopaedia Brittanica (9th ed.)[B]etween a cogent and enlightened "realism" and a sophisticated "instrumentalism" there is no significant difference-no difference that makes a difference.

Understanding quantum mechanics: a review and synthesis in precise language

“…In presentism only the present is real [71]. Deciding on the best metaphysical approach to spacetime may depend on the specific context [72]. It is not clear which, if any, of these approaches is best suited to quantum mechanics [68,71], in which the mathematical formalisms neither depend on, nor necessarily involve, the concept of spacetime [68].…”

The Hole Argument Against Everything

“…As an example of how to extend the Hole Argument to everything, consider a world like our own but which also contains certain objects which I will call "persons". 7 For the sake of argument, assume that a single person exists at different places and times and does so by having a soul. According to this metaphysics, souls are a kind of non-physical substance which distinguish persons from one another.…”

“…I assume, however, that empirical content is sufficient for physical content. 15 For related remarks see [14,7].…”

Structuralism in the philosophy of physics

“…Despite the focus in the literature on the structural nature of spacetime points (as discussed above), structuralism about spacetime need not recognize these latter as genuine physical relata of the spacetime or world structure. More broadly, even if one considers that the traditional debate between substantivalism and relationalism is actually not physically genuine and fruitful, spacetime structuralism remains a genuine ontological conception about the structural nature of the spatiotemporal (and gravitational) aspects of the world (see Dorato, ; structuralism in this broad sense would even fit into the critical and pragmatic stance of Curiel, —note that these two authors make explicit reference to Howard Stein's conception of spacetime).…”