This paper engages with the following closely related questions that have recently received some attention in the literature: what is the status of the equivalence principle in general relativity?; how does the metric field obtain its property of being able to act as a metric?; and is the metric of GR derivative on the dynamics of the matter fields? The paper attempts to complement these debates by studying the spin-2 approach to gravity. In particular, the paper argues that three lessons (...) can be drawn from the spin-2 approach: different from what is sometimes claimed in the literature, central aspects of the non-linear theory of GR are already derivable in classical spin-2 theory; in particular, ‘universal coupling’ can be considered a derived ‘theorem’ in both the classical and the quantum spin-2 approach; this provides new insights for the investigation of the equivalence principle; the ‘second miracle’ that Read et al. argue characterises GR is explained in the classical as well as in the quantum version of the spin-2 approach; the spin-2 approach allows for an ontological reduction of the metrical part of spacetime to the dynamics of matter fields. (shrink)

According to the standard model of cosmology, Λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda $$\end{document}CDM, the mass-energy budget of the current stage of the universe is not dominated by the luminous matter that we are familiar with, but instead by some form of dark matter (and dark energy). It is thus tempting to adopt scientific realism about dark matter. However, there are barely any constraints on the myriad of possible properties of this entity—it is not even certain (...) that it is a form of matter. In light of this underdetermination I advocate caution: we should not (yet) be dark matter realists. The “not(-yet)-realism” that I have in mind is different from Hacking’s (Philos Sci 56 (4), 555–581, 1989) anti-realism, in that it is semantic rather than epistemological. It also differs from the semantic anti-realism of logical empiricism, in that it is naturalistic, such that it may only be temporary and does not automatically apply to all other unobservables (or even just to all other astronomical unobservables, as with Hacking’s anti-realism). The argument is illustrated with the analogy of the much longer history of the concept of a gene, as the current state of the concept of dark matter resembles in some relevant ways that of the early concept of genes. (shrink)

Many areas of frontier physics are confronted with the crisis of a lack of accessible, direct evidence. As a result, direct model building has failed to lead to any new empirical discoveries. In this paper I argue that these areas of frontier physics have developed common methods for turning precision measurements of known quantities into potential evidence for anomalies hinting at new physics. This method of framework generalization has arisen as a sort of model-independent method for generalizing beyond known physics (...) and organizing experimental searches. I argue that this method is well-justified given the current epistemic landscape, and that theory construction in general is much broader than simply building new dynamical models. (shrink)

While $$\Lambda $$ Λ CDM has emerged as the standard model of cosmology, a small group of physicists defends modified newtonian dynamics (MOND) as an alternative view on cosmology. Exponents of MOND have employed a broad, at times explicitly philosophical, conceptual perspective in arguing their case. This paper offers reasons why that MONDian defense has been ineffective. First, we argue that the defense is ineffective according to Popperian or Lakatosian views–ostensibly the preferred philosophical views on theory assessment of proponents of (...) MOND. Second, we argue that the defense of MOND can instead best be reconstructed as an instance of meta-empirical theory assessment. The formal employment of meta-empirical assessment by MONDians is unconvincing, however, because it lacks a sufficient epistemic foundation. Specifically, the MONDian No Alternatives Argument relies on falsifiability or explanation conditions that lack epistemic relevance, while the argument from Unexpected Explanatory Success fails since there is a known alternative to MOND. In the last part of the paper, we draw some lessons for applications of meta-empirical assessment more generally. (shrink)

Super-substantivalism (of the type we’ll consider) roughly comprises two core tenets: (1) the physical properties which we attribute to matter (e.g. charge or mass) can be attributed to spacetime directly, with no need for matter as an extraneous carrier “on top of” spacetime; (2) spacetime is more fundamental than (ontologically prior to) matter. In the present paper, we revisit a recent argument in favour of super-substantivalism, based on General Relativity. A critique is offered that highlights the difference between (various accounts (...) of) fundamentality and (various forms of) ontological dependence. This affords a metaphysically more perspicuous view of what super-substantivalism’s tenets actually assert, and how it may be defended. We tentatively propose a re-formulation of the original argument that not only seems to apply to all classical physics, but also chimes with a standard interpretation of spacetime theories in the philosophy of physics. (shrink)