This paper was presented in the session on ‘Long Waves in Political Economy’ organised by Ingo Schmidt at the Congress of the Humanities and Social Sciences, Ottawa, June 1-4 2015. It discusses the ‘theoretical turn’ towards state intervention in the last Great Depression and the need for clarity about the underlying views of Keynes and Schumpeter – two of the major opposed players in that theoretical turn. It argues that primary function of economics as an esoteric discipline disguises the essence of these underlying theoretical positions. Thus in order to make a rational and evidence-based connection between theory and policy, attention both to interpretation and to assertive pluralism is indispensable.