 Feyerabend defended a realism according to which “the interpretation of a scientific theory depends upon nothing but the state of affairs it describes” (Philosophical Papers, Volume 1, p. 42). At the same time he claimed to find in Wittgenstein’s Philosophical Investigations a contextual theory of meaning according to which the meaning of terms is determined not by their use, nor by their connection with experience, but by the role they play in the wider context of a theory or explanation. Thesis I, the key proposition of Feyerabend’s early work, is supposed to encapsulate both the contextual theory of meaning and scientific realism. Only realism, by insisting on interpreting theories in their most vulnerable form as universally-quantified statements which strive for truth, leads to scientific progress instead of stagnation, he argued. Only realism allows us to live up to the highest intellectual ideals of critical attitude, honesty, and testability.