 In perhaps the most important of these early publications, “An Attempt at a Realistic Interpretation of Experience” (1958), Feyerabend argued against positivism and in favour of a scientific realist account of the relation between theory and experience, largely on grounds familiar from Karl Popper’s falsificationist views. Positivist theories of meaning, he complained, have consequences which are “at variance with scientific method and reasonable philosophy” (Philosophical Papers, Volume 1, p. 17). In particular, they imply what Feyerabend dubbed the “stability thesis”, that even major changes in theory will not affect the meanings of terms in the scientific observation-language. Against this supposition, Feyerabend defended what he called “Thesis I”, the idea that