There is a long history of governments with activist policy agendas, and they have had no shortage of economists to offer them advice. But the economic approaches Keynes developed or amplified, inspired by a respect he and many other economists held for the Soviet and German planning systems, provided a major boost to legitimising government economic policy activism. As well as a belief in a greater role for planning, Keynesianism also reflected a popular belief that free enterprise entailed considerable waste and that the Great Depression was evidence that it could become chronically unstable. From the 1920s at least until…