James Weatherall

It is deeply entrenched dogma that relativity theory prohibits superluminal propagation. It is also experimentally well-established that under some circumstances, classical electromagnetic fields propagate through a dielectric medium with superluminal group velocities and superluminal phase velocities. But it is usually claimed that these superluminal velocities do not violate the relativistic prohibition. Here I analyze electromagnetic fields in a dielectric medium within a framework for understanding superluminal propagation recently developed by Geroch and elaborated by Earman. I will argue that for some parameter values, electromagnetic fields do propagate superluminally in the Geroch-Earman sense

Soon after the 2008 financial crisis, Gillian Tett, an anthropologist and the US Managing Editor of the Financial Times, suggested that regulators’ and practitioners’ inability to anticipate and respond to deep problems in the financial industry could be traced back to what she called “silo thinking,” wherein experts in one area know nothing about the methods and research of other areas. As she put it, “the essential challenges for investors today…”—and, we might add, for regulators and academics—is “to understand the micro-details of the silos, and see how all the macro-pieces add up”.In years since, many researchers in many fields have sought to identify causes of the...

I consider two usages of the expression "gauge theory". On one, a gauge theory is a theory with excess structure; on the other, a gauge theory is any theory appropriately related to classical electromagnetism. I make precise one sense in which one formulation of electromagnetism, the paradigmatic gauge theory on both usages, may be understood to have excess structure, and then argue that gauge theories on the second usage, including Yang-Mills theory and general relativity, do not generally have excess structure in this sense.

A new reading of G.E. Moore's ‘Proof of an External World’ is offered, on which the Proof is understood as a unique and essential part of an anti-sceptical strategy that Moore worked out early in his career and developed in various forms, from 1909 until his death in 1958. I begin by ignoring the Proof and by developing a reading of Moore's broader response to scepticism. The bulk of the article is then devoted to understanding what role the Proof plays in Moore's strategy, and how that role is played.