This chapter outlines the Frankfurt School conceptions of ideology critique and critical theory. It gives an account of the “positivism dispute” in 1960s Germany between Popper and the Frankfurt School. This account indicates that the “dispute” was largely framed around a misunderstanding of the implications of Popper’s position. The discussion focusses on the Frankfurt School position on the impossibility of disinterested “scientific” knowledge in the social sciences. Popper’s contribution to the dispute suggests that the doctrine of falsifiability does not necessarily involve a “positivist” and scientistic fetishization of the form of natural scientific methods and that the nature of the “disinterest” implied in the demarcation of scientificity does not preclude a self-reflexive acknowledgement of values and interests.