 Although Feyerabend first used the term ‘incommensurable’ to describe successive scientific theories in 1962, he had been developing his conception of incommensurability for about a decade prior to meeting Kuhn in the late 1950s. According to Feyerabend, he first discussed his notion of incommensurable concepts with the Kraft Circle from 1949–1951, while working toward his doctoral thesis on protocol statements (Feyerabend 1951). The Kraft Circle was a student group named after Feyerabend’s Ph.D. supervisor Viktor Kraft, which was modeled after the Vienna Circle of which Kraft had been a member. Prominent guests such as Elizabeth Anscombe and Ludwig Wittgenstein attended some meetings (Feyerabend 1978, 108ff., 115–116; 1993, 259–260; 1995, 92). Feyerabend traced the origins of his conception of incommensurability to those ideas as represented by ‘thesis I’ in “An attempt at a realistic interpretation of experience” (1958a), which is a condensed version of his 1951 doctoral thesis.