Eleanor Knox (King's College London)
This paper discusses the distinction between internal and external symmetries. I argue (in line with the suggestions of the other papers at the symposium) that no purely mathematical distinction between these symmetries can be made. Instead, the distinction can only be upheld if one has an independent criterion for what counts as a spatiotemporal variable. Spacetime functionalism, which identifies as spacetime whatever defines a structure of inertial frames within a theory, provides such a criterion. The paper will illustrate the internal/external symmetry distinction with reference to Newton-Cartan theory and Teleparallel gravity.
