Equivalent Theories and Ontological Commitment

Abstract The literature on theoretical equivalence in philosophy of physics is replete with physical theories that look quite different but are purportedly equivalent. Plausibly, there might exist a pair of equivalent theories that look different insofar as they existentially quantify over different entities. However, given the preeminence of the quantificational theory of ontological commitment, which tells us to look to quantified entities to inform ontology, such a pair of theories seems to be a problem. In this paper, I argue that there is no good way out of the problem, and I reject the quantificational theory of ontological commitment.