Are models our tools not our masters?

Abstract It is often claimed that one can avoid the kind of underdetermination that is a typical consequence of symmetries in physics by stipulating that symmetry-related models represent the same state of affairs (Leibniz Equivalence). But recent commentators (Dasgupta in Philos Perspect 25:115–160, 2011; Pooley in: Knox and Wilson (eds) The Routledge companion to the philosophy of physics, Routledge, Milton Park, 2021; Pooley and Read in Br J Philos Sci, 2021, https://doi.org/10.1086/718274 ; Teitel in J Philos 119:233–278, 2021) have responded that claims about the representational capacities of models are irrelevant to the issue of underdetermination, which concerns possible worlds themselves. In this paper I distinguish two versions of this objection: (1) that a theory’s formalism does not (fully) determine the space of physical possibilities, and (2) that the relevant notion of possibility is not physical possibility. I offer a refutation of each.