 Albert Einstein used the term ‘incommensurable’ to apply specifically to difficulties selecting and evaluating scientific theories before Kuhn and Feyerabend, and there are strong reasons to believe that Feyerabend’s development of incommensurability was directly inspired by Einstein’s use of the term (Oberheim 2016). In his ‘Autobiographical notes’ (1949), Einstein attempted to explain that assessing the relative merits of universal physical theories involves making difficult judgments about their ‘naturalness’ that requires making judgments based on the reciprocal weighing of incommensurable qualities: “The second point of view is not concerned with the relation to the material observation but with the premises of the theory itself, with what may briefly but vaguely be characterized as the ‘naturalness’ or ‘logical simplicity’ of the premises (of the basic concepts and of the relations between these which are taken as a basis). This point of view, an exact formulation of which meets with great difficulties, has played an important role in the selection and evaluation of theories since time immemorial. The problem here is not simply one of a kind of enumeration of the logically independent premises (if anything like this were at all unequivocally possible), but that of a kind of reciprocal weighing of incommensurable qualities” (1949a, 23).