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It is widely accepted by physicists and philosophers of physics alike that there are certain contexts in which general relativity will "break down". In such cases, one expects to need some as-yet undiscovered successor theory. This paper will discuss certain pathologies of general relativity that might be taken to signal that the theory is breaking down, and consider how one might expect a successor theory to do better. The upshot will be an unconventional interpretation of the "Strong Cosmic Censorship Hypothesis"., Comment: 15 pages

In this paper I bring the recent philosophical literature on theoretical equivalence to bear on dualities in physics. Focusing on electromagnetic duality, which is a simple example of S-duality in string theory, I will show that the duality fits naturally into at least one framework for assessing equivalence---that of categorical equivalence---but that it fails to meet a necessary condition for equivalence on that account. The reason is that the duality does not preserve "empirical content" in the required sense; instead, it takes models to models with "dual" empirical content. I conclude by discussing how one might react to this., Comment: 15 pages; given as part of a symposium at the 2018 PSA meeting. This version corrects an error in the previous version wherein a quote was misattributed to Polchinski (2017)

Why do people who disagree about one subject tend to disagree about other subjects as well? In this paper, we introduce a model to explore this phenomenon of ‘epistemic factionization’. Agents attempt to discover the truth about multiple propositions by testing the world and sharing evidence gathered. But agents tend to mistrust evidence shared by those who do not hold similar beliefs. This mistrust leads to the endogenous emergence of factions of agents with multiple, highly correlated, polarized beliefs.

This special issue of Foundations of Physics collects together articles representing some recent new perspectives on the hole argument in the history and philosophy of physics. Our task here is to introduce those new perspectives.

Scientists are generally subject to social pressures, including pressures to conform with others in their communities, that affect achievement of their epistemic goals. Here we analyze a network epistemology model in which agents, all else being equal, prefer to take actions that conform with those of their neighbors. This preference for conformity interacts with the agents’ beliefs about which of two (or more) possible actions yields the better result. We find a range of possible outcomes, including stable polarization in belief and action. The model results are sensitive to network structure. In general, though, conformity has a negative effect on a community’s ability to reach accurate consensus about the world.

We provide a novel perspective on “regularity” as a property of representations of the Weyl algebra. In Part I, we critiqued a proposal by Halvorson [2004, “Complementarity of representations in quantum mechanics”, Studies in History and Philosophy of Modern Physics 35 (1), pp. 45–56], who advocates for the use of the non-regular “position” and “momentum” representations of the Weyl algebra. Halvorson argues that the existence of these non-regular representations demonstrates that a quantum mechanical particle can have definite values for position or momentum, contrary to a widespread view. In this sequel, we propose a justification for focusing on regular representations, pace Halvorson, by drawing on algebraic methods.

The Black-Scholes(-Merton) model of options pricing establishes a theoretical relationship between the “fair” price of an option and other parameters characterizing the option and prevailing market conditions. Here I discuss a common application of the model with the following striking feature: the (expected) output of analysis apparently contradicts one of the core assumptions of the model on which the analysis is based. I will present several attitudes one might take toward this situation and argue that it reveals ways in which a “broken” model can nonetheless provide useful (and tradeable) information.

The COVID-19 pandemic has created enormously difficult decisions for individuals trying to navigate both the risks of the pandemic and the demands of everyday life. Good decision making in such scenarios can have life and death consequences. For this reason, it is important to understand what drives risk assessments during a pandemic, and, in particular, to investigate the ways that these assessments might deviate from ideal risk assessments. Two studies (N = 841) investigate risk judgments related to COVID-19. The results indicate that risk judgments are sensitive to factors unrelated to the objective risks of infection. In particular, activities that are morally justified are perceived as safer while those that might subject people to blame, or culpability, are seen as riskier.

In recent years philosophers of science have explored categorical equivalence as a promising criterion for when two (physical) theories are equivalent. On the one hand, philosophers have presented several examples of theories whose relationships seem to be clarified using these categorical methods. On the other hand, philosophers and logicians have studied the relationships, particularly in the first order case, between categorical equivalence and other notions of equivalence of theories, including definitional equivalence and generalized definitional (aka Morita) equivalence. In this article, I will express some skepticism about this approach, both on technical grounds and conceptual ones. I will argue that "category structure" (alone) likely does not capture the structure of a theory, and discuss some recent work in light of this claim.

In their recent book Merchants of Doubt [New York:Bloomsbury 2010], Naomi Oreskes and Erik Conway describe the "tobacco strategy" , which was used by the tobacco industry to influence policy makers regarding the health risks of tobacco products. The strategy involved two parts, consisting of (1) promoting and sharing independent research supporting the industry's preferred position and (2) funding additional research, but selectively publishing the results. We introduce a model of the Tobacco Strategy, and use it to argue that both prongs of the strategy can be extremely effective—even when policy makers rationally update on all evidence available to them. As we elaborate, this model helps illustrate the conditions under which the Tobacco Strategy is particularly successful. In addition, we show how journalists engaged in "fair" reporting can inadvertently mimic the effects of industry on public belief.

I critically discuss two dogmas of the "dynamical approach" to spacetime in general relativity, as advanced by Harvey Brown [Physical Relativity (2005) Oxford:Oxford University Press] and collaborators. The first dogma is that positing a "spacetime geometry" has no implications for the behavior of matter. The second dogma is that postulating the "Strong Equivalence Principle" suffices to ensure that matter is "adapted" to spacetime geometry. I conclude by discussing "spacetime functionalism". The discussion is presented in reaction to and sympathy with recent work by James Read ["Explanation, geometry, and conspiracy in relativity theory"(20??) Thinking about Spacetime. Boston: Birkauser]., 33 pages

We use models and historical cases to try and understand some of the ways scientific beliefs can go wrong. In particular, we consider questions like: how do conformity and social trust influence the spread of beliefs? What is the ideal network structure for a scientific community? And how do industrial propagandists influence the progress of science, as well as public belief?

A classic problem in general relativity, long studied by both physicists and philosophers of physics, concerns whether the geodesic principle may be derived from other principles of the theory, or must be posited independently. In a recent paper [Geroch & Weatherall, “The Motion of Small Bodies in Space-Time,” Comm. Math. Phys. (forthcoming)], Bob Geroch and I have introduced a new approach to this problem, based on a notion we call “tracking.” In the present paper, I situate the main results of that paper with respect to two other, related approaches, and then make some preliminary remarks on the interpretational significance of the new approach. My main suggestion is that “tracking” provides the resources for eliminating “point particles”—a problematic notion in general relativity—from the geodesic principle altogether.

Scientists are generally subject to social pressures, including pressures to conform with others in their communities, that affect achievement of their epistemic goals. Here we analyze a network epistemology model in which agents, all else being equal, prefer to take actions that conform with those of their neighbors. This preference for conformity interacts with the agents' beliefs about which of two (or more) possible actions yields the better outcome. We find a range of possible outcomes, including stable polarization in belief and action. The model results are sensitive to network structure. In general, though, conformity has a negative effect on a community's ability to reach accurate consensus about the world.

We consider the motion of small bodies in general relativity. The key result captures a sense in which such bodies follow timelike geodesics (or, in the case of charged bodies, Lorentz-force curves). This result clarifies the relationship between approaches that model such bodies as distributions supported on a curve, and those that employ smooth fields supported in small neighborhoods of a curve. This result also applies to "bodies" constructed from wave packets of Maxwell or Klein-Gordon fields. There follows a simple and precise formulation of the optical limit for Maxwell fields., 30 pages, forthcoming in Communications in Mathematical Physics

Michael Weisberg’s Simulation and Similarity reflects the state of the art in the philosophical literature on scientific models. It presents an account of modeling that aims to accommodate essentially all examples of scientific models discussed in the extant philosophical literature, and many more besides. The view that results is pluralist, in the sense that Weisberg tends to divide and conquer. He recognizes three broad classes of models, and within each class, he identifies multiple sub-classes. Cutting across these classes, he draws distinctions between “targeted” and “untargeted” modeling practices, and analyzes these separately. Cutting in yet another direction, he identifies three varieties of idealization, which he argues function in different ways, but all of which involve some kind of distortion of the model with respect to its target. Many of these distinctions are intended to broaden the tent, to draw attention to features of the practice that others have neglected: the philosophical literature, he argues, has tended to focus on a few kinds of model, rather than addressing the breadth of modeling practice. All of this is to the good: drawing attention to the richness and diversity of models in the wild is a valuable contribution in itself, and faced with this diversity, his pluralism serves him well. There are also striking successes in his attempts to regiment the subject. Indeed, the framework he has devised has already given form to the modeling literature in the wake of the book. He has set the terms for future work on this subject. Perhaps it goes without saying that this is a major accomplishment on two counts: the book succeeds in its goal of

We consider various curious features of general relativity, and relativistic field theory, in two spacetime dimensions. In particular, we discuss: the vanishing of the Einstein tensor; the failure of an initial-value formulation for vacuum spacetimes; the status of singularity theorems; the non-existence of a Newtonian limit; the status of the cosmological constant; and the character of matter fields, including perfect fluids and electromagnetic fields. We conclude with a discussion of what constrains our understanding of physics in different dimensions., 31 pages, 1 figure

I argue that the Hole Argument is based on a misleading use of the mathematical formalism of general relativity. If one is attentive to mathematical practice, I will argue, the Hole Argument is blocked., 27 pages

There are well-known problems associated with the idea of (local) gravitational energy in general relativity. We offer a new perspective on those problems by comparison with Newtonian gravitation, and particularly geometrized Newtonian gravitation (i.e., Newton-Cartan theory). We show that there is a natural candidate for the energy density of a Newtonian gravitational field. But we observe that this quantity is gauge dependent, and that it cannot be defined in the geometrized (gauge-free) theory without introducing further structure. We then address a potential response by showing that there is an analogue to the Weyl tensor in geometrized Newtonian gravitation., Comment: 30 pages; derived from a paper presented at the 2016 UK/EU Foundations of Physics Conference in London, UK

I review some recent work on applications of category theory to questions concerning theoretical structure and theoretical equivalence of classical field theories, including Newtonian gravitation, general relativity, and Yang–Mills theories. In particular, the chapter explains how the Baez–Bartel–Dolan framework for classifying forgetful functors provides a precise way of saying when one formulation of a physical theory posits more or less structure than another, and also when two theories posit equivalent amounts of structure.

We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin's response to it., 18 pages; 8 figures. Forthcoming in Foundations of Physics

The celu of the philosophical literature on the hole argument is the 1987 paper by Earman \& Norton ["What Price Space-time Substantivalism? The Hole Story" Br. J. Phil. Sci.]. This paper has a well-known back-story, concerning work by Stachel and Norton on Einstein's thinking in the years 1913-15. Less well-known is a connection between the hole argument and Earman's work on Leibniz in the 1970s and 1980s, which in turn can be traced to an argument first presented in 1975 by Howard Stein. Remarkably, this thread originates with a misattribution: the argument Earman attributes to Stein, which ultimately morphs into the hole argument, was not the argument Stein gave. The present paper explores this episode and presents some reflections on how it bears on the subsequent literature., 28 pages. Forthcoming in Studies in History and Philosophy of Modern Physics

In their recent book Merchants of Doubt [New York:Bloomsbury 2010], Naomi Oreskes and Erik Conway describe the "tobacco strategy", which was used by the tobacco industry to influence policy makers regarding the health risks of tobacco products. The strategy involved two parts, consisting of (1) promoting and sharing independent research supporting the industry's preferred position and (2) funding additional research, but selectively publishing the results. We introduce a model of the Tobacco Strategy, and use it to argue that both prongs of the strategy can be extremely effective--even when policy makers rationally update on all evidence available to them. As we elaborate, this model helps illustrate the conditions under which the Tobacco Strategy is particularly successful. In addition, we show how journalists engaged in "fair" reporting can inadvertently mimic the effects of industry on public belief., Comment: 26 pages, 9 figures, forthcoming in the British Journal for Philosophy of Science

Why do people who disagree about one subject tend to disagree about other subjects as well? In this paper, we introduce a network epistemology model to explore this phenomenon of “epistemic factionization”. Agents attempt to discover the truth about multiple beliefs by testing the world and sharing evidence gathered. But agents tend to mistrust evidence shared by those who do not hold similar beliefs. This mistrust leads to the endogenous emergence of factions of agents with multiple, highly correlated, polarized beliefs.

Laura Ruetsche, Interpreting Quantum Theories. Oxford: Oxford University Press. Pp. xvii, 377. Most philosophical work on quantum physics has concerned simple systems. And for good reason. Even one or two particle systems can exhibit the striking features we have come to associate with quantum physics—features such as entanglement, interference, and non-locality. But as far as physics goes, such systems barely scrape the surface. In particular, they have only a finite number of degrees of freedom, which means their states are characterized by a finite number of independent parameters. The systems studied in fields such as high energy particle physics and many-body physics, meanwhile, have uncountably many degrees of freedom. They are far more complicated than the usual philosophical fare. This is untroubling as long as the conceptual heart of quantum physics can be effectively condensed down. But what if philosophers’ toy systems are fundamentally different from realistic ones? That would be a problem. And indeed, as Laura Ruetsche convincingly argues in Interpreting Quantum Theories, systems with uncountable degrees of freedom—what Ruetsche collectively calls QM ∞ —are fundamentally different from the systems that have become the stock and trade of philosophy of physics, in ways that change the interpretational project. Ruetsche’s book does two things exceedingly well. The first is to provides a (comparatively) accessible and philosophically-oriented introduction to the algebraic approach to quantum physics, which is essential for understanding QM ∞ . This is a valuable contribution. The algebraic approach is the setting for much recent philosophical work. And yet learning it is notoriously difficult, as even pedagogical texts are aimed at research-level mathematicians. Ruetsche’s book is technically demanding, but it works to bring non-mathematicians along. It is, without a doubt, the best place to enter this literature. Second, the book sets the agenda for future work on QM ∞ , by effectively and judiciously drawing important foundational questions out of a sprawling and difficult physics literature. In this regard, it is a close cousin to John Earman’s excellent Bangs, Crunches, Whimpers, and Shrieks, which has had a significant influence on subsequent philosophy of spacetime physics. 1 Philosophers of physics will be addressing the questions Ruetsche has raised, in many cases for the first time, for years to come. Interpreting Quantum Theories centers on what might be called the problem of inequivalent representations. The quantum theories that philosophers are accustomed to are set in a mathematical structure known as a (separable) Hilbert space, which is an at-most countably infinite dimensional complex vector space. Rays in a Hilbert space represent possible states of a physical system, and self- adjoint operators on that Hilbert space correspond to properties of the system. 1 John Earman, Bangs, Crunches, Whimpers, and Shrieks (Oxford: Oxford University Press, 1995).

I provide an alternative characterization of a "standard of rotation" in the context of classical spacetime structure that does not refer to any covariant derivative operator., 13 pages

This chapter reports findings from an interdisciplinary investigation of charitable giving. The authors studied charity contributions using a Dictator Game experimental design whereby participants are given tokens with real money value and can decide to contribute to charity or to keep the money for themselves. But to get a better sense of the role of morals and emotions, they also asked participants to explain their motivations for giving. In addition, they conducted the experiment with the same student participants at two different points in time. They found that those who contribute more to charity tend to be women, tend to evaluate themselves as less self-interested, and are more likely to have been those who gave to charity at the first point in time. The choices of particular charities are not very consistent over time but depend on participants' moral and emotional evaluations. The chapter concludes that even in abstract experimental conditions, moral judgments and emotional underpinnings are not discrete influences on how people think about and use money but are thoroughly intertwined, relationally grounded, and reinforced by practice.

As Harvey Brown emphasizes in his book Physical Relativity, inertial motion in general relativity is best understood as a theorem, and not a postulate. Here I discuss the status of the "conservation condition", which states that the energy-momentum tensor associated with non-interacting matter is covariantly divergence-free, in connection with such theorems. I argue that the conservation condition is best understood as a consequence of the differential equations governing the evolution of matter in general relativity and many other theories. I conclude by discussing what it means to posit a certain spacetime geometry and the relationship between that geometry and the dynamical properties of matter., 48 pages; Forthcoming in Studies in History and Philosophy of Modern Physics

Contemporary societies are often "polarized", in the sense that sub-groups within these societies hold stably opposing beliefs, even when there is a fact of the matter. Extant models of polarization do not capture the idea that some beliefs are true and others false. Here we present a model, based on the network epistemology framework of Bala and Goyal ["Learning from neighbors", \textit{Rev. Econ. Stud.} \textbf{65}(3), 784-811 (1998)], in which polarization emerges even though agents gather evidence about their beliefs, and true belief yields a pay-off advantage. The key mechanism that generates polarization involves treating evidence generated by other agents as uncertain when their beliefs are relatively different from one's own., Comment: 22 pages, 5 figures, author final version

We study the Johansen-Ledoit-Sornette (JLS) model of financial market crashes (Johansen, Ledoit, and Sornette [2000] "Crashes as Critical Points." Int. J. Theor. Appl. Finan. 3(2) 219-255). On our view, the JLS model is a curious case from the perspective of the recent philosophy of science literature, as it is naturally construed as a "minimal model" in the sense of Batterman and Rice (Batterman and Rice [2014] "Minimal Model Explanations." Phil. Sci. 81(3): 349-376) that nonetheless provides a causal explanation of market crashes, in the sense of Woodward's interventionist account of causation (Woodward [2003]. Making Things Happen. Oxford:Oxford University Press)., Comment: 32 pages

I argue that a criterion of theoretical equivalence due to Clark Glymour [Nous 11(3), 227-251 (1977)] does not capture an important sense in which two theories may be equivalent. I then motivate and state an alternative criterion that does capture the sense of equivalence I have in mind. The principal claim of the paper is that relative to this second criterion, the answer to the question posed in the title is "yes", at least on one natural understanding of Newtonian gravitation., Comment: 27 pages

© 2015, Springer Science+Business Media Dordrecht. I articulate and discuss a geometrical interpretation of Yang–Mills theory. Analogies and disanalogies between Yang–Mills theory and general relativity are also considered.

© 2016 by The Massachusetts Institute of Technology. The 2008 financial crisis revealed that key players in finance, regulation, and the academy failed to understand realities outside their own area of expertise. Within the academy, scholars from an increasing number of disciplines study finance, and yet few of them seem to be in conversation. Perhaps understandably, given the complexity of a phenomenon such as “financial crisis,” no single discipline has yet offered an adequate analysis of what happened in 2008, or what could help prevent another such systemic threat to the economy. In this article, we argue that developing more effective capacity to comprehend and regulate financial markets requires an interdisciplinary approach that moves beyond pluralism and tolerance of other approaches. Rather, in-depth critical engagement with the underlying assumptions, methods, and findings across fields of research and practice is needed. To advance this argument, we discuss four specific, connected intra-disciplinary projects in progress, and show how key assumptions underlying approaches in each are revealed and revised through systematic engagement with other fields.

© 2016 by the Philosophy of Science Association. All rights reserved. I address a question recently raised by Simon Saunders concerning the relationship between the space-time structure of Newton-Cartan theory and that of what I will call “Maxwell-Huygens space-time.” This discussion will also clarify a connection between Saunders’s work and a recent paper by Eleanor Knox.