The history of political economy is punctuated by outstanding and passionate figures, many of them English—Reverend Thomas R. Malthus pleading for population restraint among the working classes; stockbroker David Ricardo fighting the protectionist Corn Laws and ushering in an era of free trade. Joan Robinson belongs on this list of outstanding and passionate English economists. For more than fifty years of the twentieth century, her living influence was felt wherever economics was taught or discussed. t Cambridge, economics was considered to be one of the moral sciences and was treated as a study of the causes of material welfare, a part of the long tradition established by Adam Smith's Wealth of Nations. Economics in North America was less unified than at Cambridge. While Marshall's theory was dominant, the European marginalists were also a strong influence.