 At the University of Vienna, although he had originally planned to submit a thesis on physics, Feyerabend swapped to philosophy when he got nowhere with the electrodynamics problem he was calculating (the philosopher of science as failed scientist?). He completed his doctoral thesis, “Zur Theorie der Basissätze” in 1951 under Kraft’s supervision. The subject of the thesis was “basic sentences”, or “protocol sentences”, i.e. the kind of sentences that, the Logical Positivists had theorised, comprise the foundations of scientific knowledge. He later reported that in his philosophical work he had “started from and returned to the discussion of protocol statements in the Vienna Circle” (“Concluding Unphilosophical Conversation”, in Munévar (1991), p. 526). This is unsurprising, given that Kraft was then the Vienna Circle’s only survivor in Vienna. However, Kraft’s influence on Feyerabend has only recently been emphasised. Much of the material from Feyerabend’s thesis was presented at (or gleaned from) meetings of the Kraft Circle, and also appears in his early articles, such as “An Attempt at a Realistic Interpretation of Experience” (1958). The thesis itself was “a condensed version of the discussions in the Kraft Circle” (p. 115).