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Caspar Jacobs
Leiden University
  1. Invariance, intrinsicality and perspicuity.Caspar Jacobs - 2022 - Synthese 200 (2):1-17.
    It is now standard to interpret symmetry-related models of physical theories as representing the same state of affairs. Recently, a debate has sprung up around the question when this interpretational move is warranted. In particular, Møller-Nielsen :1253–1264, 2017) has argued that one is only allowed to interpret symmetry-related models as physically equivalent when one has a characterisation of their common content. I disambiguate two versions of this claim. On the first, a perspicuous interpretation is required: an account of the models’ (...)
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  2. Invariance or equivalence: a tale of two principles.Caspar Jacobs - 2021 - Synthese 199 (3-4):9337-9357.
    The presence of symmetries in physical theories implies a pernicious form of underdetermination. In order to avoid this theoretical vice, philosophers often espouse a principle called Leibniz Equivalence, which states that symmetry-related models represent the same state of affairs. Moreover, philosophers have claimed that the existence of non-trivial symmetries motivates us to accept the Invariance Principle, which states that quantities that vary under a theory’s symmetries aren’t physically real. Leibniz Equivalence and the Invariance Principle are often seen as part of (...)
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  3.  18
    Absolute Velocities Are Unmeasurable: Response to Middleton and Murgueitio Ramírez.Caspar Jacobs - 2022 - Australasian Journal of Philosophy 100 (1):202-206.
    ABSTRACT In this journal, Middleton and Murgueitio Ramírez argue that absolute velocity is measurable, contrary to the received wisdom. Specifically, they claim that ‘there exists at least one reasonable analysis of measurement according to which the speedometer in [a world called “the Basic World”] measures the absolute velocity of the car.’ In this note, I critically respond to that claim: the analysis of measurement that Middleton and Murgueitio Ramírez propose is not reasonable; nor does it entail that absolute velocities are (...)
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  4. The Coalescence Approach to Inequivalent Representation: Pre-QM ∞ Parallels.Caspar Jacobs - 2023 - British Journal for the Philosophy of Science 74 (4):1069-1090.
    Ruetsche ([2011]) argues that the occurrence of unitarily inequivalent representations in quantum theories with infinitely many degrees of freedom poses a novel interpretational problem. According to Ruetsche, such theories compel us to reject the so-called ideal of pristine interpretation; she puts forward the ‘coalescence approach’ as an alternative. In this paper I offer a novel defence of the coalescence approach. The defence rests on the claim that the ideal of pristine interpretation already fails before one considers the peculiarities of QM∞: (...)
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  5.  87
    In Defence of Dimensions.Caspar Jacobs - forthcoming - British Journal for the Philosophy of Science.
    The distinction between dimensions and units in physics is commonplace. But are dimensions a feature of reality? The most widely-held view is that they are no more than a tool for keeping track of the values of quantities under a change of units. This anti-realist position is supported by an argument from underdetermination: one can assign dimensions to quantities in many different ways, all of which are empirically equivalent. In contrast, I defend a form of dimensional realism, on which some (...)
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  6. The Nature of a Constant of Nature: the Case of G.Caspar Jacobs - 2022 - Philosophy of Science 90 (4):797-81.
    Physics presents us with a symphony of natural constants: G, h, c, etc. Up to this point, constants have received comparatively little philosophical attention. In this paper I provide an account of dimensionful constants, in particular the gravitational constant. I propose that they represent inter-quantity structure in the form of relations between quantities with different dimensions. I use this account of G to settle a debate over whether mass scalings are symmetries of Newtonian Gravitation. I argue that they are not, (...)
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  7.  80
    Du Chatelet: Idealist about extension, bodies and space.Caspar Jacobs - 2020 - Studies in History and Philosophy of Science Part A 82:66-74.
    - Emilie du Châtelet offers an interesting and unusual account of the origin of our representation of extension. - She is an idealist about the essence extension, bodies and space, regarding them as mental constructs. - Du Châtelet's account requires a brute fact about the mind, in apparent tension with the Principle of Sufficient Reason.
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  8. Are Models Our Tools Not Our Masters?Caspar Jacobs - 2023 - Synthese 202 (4):1-21.
    It is often claimed that one can avoid the kind of underdetermination that is a typical consequence of symmetries in physics by stipulating that symmetry-related models represent the same state of affairs (Leibniz Equivalence). But recent commentators (Dasgupta 2011; Pooley 2021; Pooley and Read 2021; Teitel 2021a) have responded that claims about the representational capacities of models are irrelevant to the issue of underdetermination, which concerns possible worlds themselves. In this paper I distinguish two versions of this objection: (1) that (...)
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  9. The metaphysics of fibre bundles.Caspar Jacobs - 2023 - Studies in History and Philosophy of Science Part A 97 (C):34-43.
    Recently, Dewar (2019) has suggested that one can apply the strategy of 'sophistication' - as exemplified by sophisticated substantivalism as a response to the diffeomorphism invariance of General Relativity - to gauge theories such as electrodynamics. This requires a shift to the formalism of fibre bundles. In this paper, I develop and defend this suggestion. Where my approach differs from previous discussions is that I focus on the metaphysical picture underlying the fibre bundle formalism. In particular, I aim to affirm (...)
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  10. Comparativist Theories or Conspiracy Theories: the No Miracles Argument Against Comparativism.Caspar Jacobs - forthcoming - Journal of Philosophy.
    Although physical theories routinely posit absolute quantities, such as absolute position or intrinsic mass, it seems that only comparative quantities such as distance and mass ratio are observable. But even if there are in fact only distances and mass ratios, the success of absolutist theories means that the world looks just as if there are absolute positions and intrinsic masses. If comparativism is nevertheless true, there is a sense in which it is a cosmic conspiracy that the world looks just (...)
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  11. Some Neglected Possibilities: A Reply to Teitel.Caspar Jacobs - 2024 - Journal of Philosophy 121 (2):108-120.
    The infamous Hole Argument has led philosophers to develop various versions of substantivalism, of which metric essentialism and sophisticated substantivalism are the most popular. In this journal, Trevor Teitel has recently advanced novel arguments against both positions. However, Teitel does not discuss the position of Jeremy Butterfield, which appeals to Lewisian counterpart theory in order to avoid the Hole Argument. In this note I show that the Lewis-Butterfield view is immune to Teitel’s challenges.
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  12. Are Dynamic Shifts Dynamical Symmetries?Caspar Jacobs - 2023 - Philosophy of Science 90 (5):1352-1362.
    Shifts are a well-known feature of the literature on spacetime symmetries. Recently, discussions have focused on so-called dynamic shifts, which by analogy with static and kinematic shifts enact arbitrary linear accelerations of all matter (as well as a change in the gravitational potential). But in mathematical formulations of these shifts, the analogy breaks down: while static and kinematic shift act on the matter field, the dynamic shift acts on spacetime structure instead. I formulate a different, `active' version of the dynamic (...)
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  13. How (Not) to Define Inertial Frames.Caspar Jacobs - forthcoming - Australasian Journal of Philosophy.
    It is nearly impossible to open a textbook on Newtonian mechanics without encountering the concept of inertial frames: the frames that are privileged by the theory’s dynamics. In this paper, I argue that extant definitions of inertial frames are unsatisfactory. I criticise two common definitions of inertial frames: law-based definitions, according to which inertial frames are simply those in which the laws are true, and structure-based definitions, according to which inertial frames are those that are ‘adapted’ to spatiotemporal structure. I (...)
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