Abstract

I discuss the idea of relativistic causality, i.e. the requirement that causal processes (signals) can propagate only within the light-cone. After briefly locating this requirement in the philosophy of causation, my main aim is to draw philosophers’ attention to the fact that it is subtle, and even problematic, in contemporary physics. For there are scenarios in which it fails.

I report four such scenarios from relativistic quantum physics. Two are familiar to philosophers of physics: viz. the pilot-wave approach, and the Newton-Wigner representation.

But I stress two unfamiliar examples: the Drummond-Hathrell and Scharnhorst effects. These effects also illustrate a general moral in the philosophy of geometry: that the mathematical structures, especially the metric tensor, that represent geometry get their geometric significance by dint of detailed physical arguments. My exposition of these effects, and this moral, follows Brown (2005).