Symmetry and the Scope of Scientific Realism

Abstract

Scientific realism characteristically encompasses semantic as well as epistemological claims. When a theory of modern physics is empirically successful, the realist considers this a reason to believe that it is approximately true, and that terms of the theory (including those it newly introduces) typically refer to or represent real physical structures—irrespective of whether these are accessible to our senses or independently measurable. But suppose every model of a theory may be mapped into a distinct model by a transformation that preserves all measurable structures. Then the empirical success of the theory fails to support realist claims about purportedly distinct structures related by such a symmetry. Assuming there are such structures, the theory’s success provides no reason to believe that terms it introduces determ- inately refer to or represent them, and no basis for any specific belief about them. Even a scientific realist then has no grounds for thinking there are any such struc- tures. These include Newtonian absolute space and the gauge potentials of classical electromagnetism acting on classical or quantum charged particles.