Dear all, our next speaker in the Philosophy of Science Colloquium organized by the Institute Vienna Circle is Matteo Collodel (IVC), who will give a talk on May 7, 4.45-6.15 pm. All are welcome! ---------------------------------------------------------------------------------------- *Philosophy of Science Colloquium TALK: Matteo Collodel (IVC)* Popper's Problem of Incommensurability Philosophy of Science Colloquium The Institute Vienna Circle holds a Philosophy of Science Colloquium with talks by our present fellows. * Date:* 07/05/2026 * Time:* 16h45 * Venue:* New Institute Building (NIG), Universitätsstraße 7, 1010 Wien, HS 3C * Abstract:* Despite the rich secondary literature on Kuhn's and Feyerabend's concepts of incommensurability, it has so far gone unnoticed that Popper was the first to introduce such a metaphor in 20th-century philosophy of science to refer to a methodological and conceptual issue in inter-theoretic relations. This paper aims to clarify the terms of Popper's problem of incommensurability, highlighting the crucial role it played in the development of Popper's thought. In the mid-1930s, with his Logik der Forschung, Popper advanced falsificationism as a methodological proposal for scientific research, intended to account for and promote scientific progress. In short, falsificationism is encapsulated in the rule prescribing the maximisation of the falsifiability of scientific theories, as expressed by universal statements and advanced as conjectural explanations for problem situations, by making them explanatorily and predictively more powerful, broadening their scope (universality) and/or increasing their accuracy (precision). Popper explicated both properties of a theory in terms of its "empirical content" or the class of their potential falsifiers, namely those "basic statements," or singular observation statements, inconsistent with the theory. As the empirical content of scientific theories corresponds to their degrees of falsifiability, Popper assumed that the progress of science or the growth of scientific knowledge could be comparatively evaluated on this basis. However, he also realised that such a procedure is problematic: it is feasible only when the classes of potential falsifiers of scientific theories are in a subclass relation; in contrast, "incommensurable" theories, whose empirical contents intersect or have no members in common, preclude it. In the following two decades, Popper continued to struggle with the problem of incommensurability. At the turn of the 1950s, he emphasised that, within falsificationism, as in evolutionary theory, increasing theoretical competition by proliferating the number and diversity of explanatory solutions to the same problem facilitates the progress of science through theory testing and theory selection by crucial experiments, which could sanction the corroboration of a theory and the tentative rejection of an alternative rival. At the end of the decade, however, he became dissatisfied with the metaphor of incommensurability, which was dropped in the English translation of his masterpiece and, only a few years later, at the turn of the 1960s, he thought he had finally overcome this potentially fatal issue for his methodological proposal, thanks to the concept of verisimilitude: a more formal characterisation of truthlikeness for scientific theories that compared them based on both their falsity content and their truth content — a solution that would be proved wrong in the mid-1970s. In fact, he had only paved the way for Feyerabend's concept of incommensurability.