Abstract

Isometry hypotheses are propositions that assert the constancy of a specific physical magnitude of a system under prescribed conditions. This paper addresses the controversy concerning the conventionality of this type of hypotheses. It discusses several instances of isometry hypotheses and it is shown that experimental facts can be invoked to criticise (or "refute") isometry hypotheses, just as other types of hypotheses. This proves that isometry hypotheses, and the choices of measurement standards that are grounded in such hypotheses, are not merely conventional.