Frank Gerald Shove was a close friend of Keynes and the other protagonists of the economic debates in Cambridge during the 1920s and 1930s. Shove's influence on those debates is not well documented because he published little and had all his notes destroyed after his death. This paper looks at Shove's most significant contributions to the debates of the 1930s. Attention is concentrated on the debates over increasing returns and imperfect competition. Shove emphasized the complexity of economic phenomena and the need to develop tools to deal with it. He found his analytical and methodological inspiration in Marshall's work. This position led him to clash with younger economists, in particular Joan Robinson, whose work on imperfect competitio...