General Relativity Needs No Interpretation†

I argue that, contrary to the recent claims of physicists and philosophers of physics, general relativity requires no interpretation in any substantive sense of the term. I canvass the common reasons given in favor of the alleged need for an interpretation, including the difficulty in coming to grips with the physical significance of diffeomorphism invariance and of singular structure, and the problems faced in the search for a theory of quantum gravity. I find that none of them shows any defect in our comprehension of general relativity as a physical theory. I conclude by comparing general relativity with quantum mechanics, a theory that manifestly does stand in need of an interpretation in an important sense. Although many aspects of the conceptual structure of general relativity remain poorly understood, it suffers no incoherence in its formulation as a physical theory that only an “interpretation” could resolve. †Submitted Nov 2007, accepted without revisions for publication Jul 2008. ‡I thank John Norton for penetrating remarks and hard questions, Jeremy Butterfield for insightful comments on an earlier version of the paper, Chris Pincock for a useful conversation on interpreting physical theories, and David Malament for many helpful discussions over several years on essentially every issue I discuss in the paper and especially for pressing me to clarify my notion of “interpretation”. Author’s email: [email protected]; postal address: Center for Philosophy of Science, University of Pittsburgh, 817 Cathedral of Learning, Pittsburgh, PA 15260, USA