This book addresses the revival of classical political economy in the Cambridge tradition. This framework, which explains economic activity in terms of the reproduction and distribution of a surplus produced by labour, and which has underpinned the work of authors from Adam Smith to Karl Marx, was abandoned by orthodox theory after the marginalist revolution. The marginalists promoted a different methodology from the one adopted by classical political economists, focusing on optimising behaviour under scarcity (rather than on the reproduction of a surplus), while resorting extensively to mathematical modelling. After the marginalist revolution, Alfred Marshall, perhaps the greatest Cambridge economist of all attempted to render marginalist theory compatible with classical political economy, and initiated the Cambridge economic tradition. Shaped by his contribution, a current of thinking that has informed the work of many notable Cambridge economists including John Maynard Keynes, Joan Robinson and Piero Sraffa, developed only to fall by the wayside once again in the late twentieth century. Happily, the tradition is now back in vogue through the work of Amartya Sen and the Cambridge Realist project.