The origin of this chapter was an invitation to contribute a paper on the evolution of post-war macroeconomics to a conference in Leuven, in 1988. In an attempt to provide a novel twist to the story, I tried to tell it in Lakatosian terms, applying Roy Weintraub’s idea of a neo-Walrasian research programme. On a visit to England, Weintraub pointed out that I had not succeeded, and explained to me how it should be done. I presented the resulting paper at the History of Economic Thought conference in Bristol that year, where Mark Blaug heard it and invited me to present a revised version of it at the conference in Capri in 1989. It remains the only paper in which I have worked entirely within Lakatos’s methodology of scientific research programmes. It is because it is the key to explaining the origin of the other chapters in this volume that it is reprinted here, despite having been reprinted in Backhouse (1995).