John Maynard Keynes lent his name to the most influential paradigm in the political economy of the mid-twentieth century. During the last thirty years a distinction – though not always the same distinction – has increasingly been drawn between Keynes and Keynesianism. To study Keynes himself points towards problems which are essentially biographical, just as the impact of Keynesianism indicates problems which are more broadly historical; one approach enters into disputes about intentions, while the other is more concerned with assessing outcomes; and the two projects need to be linked. Major biographies by Donald Moggridge and Robert Skidelsky have now modified important features of Sir Roy Harrod's great monument to his friend, and thereby helped to retrieve the historical Keynes: a child born in the year that Marx died, a Victorian in his eighteenth year at the end of the old queen's reign, a man of only sixty-two at his death in 1946. Recently Keynes's early beliefs of which he gave a famous account, and his work on probability, have become the focus of lively debate among historians, philosophers and economists. All of this is relevant to understanding Keynes's own conception of political economy.

The historical fate of Keynesianism is likewise now seen in a new perspective. In the period up to the 1960s, naive Keynesian triumphalism postulated a conversion to Keynes's ideas which was at once inevitable, beneficent, and permanent; since then, vulgar anti-Keynesianism has been premised on Keynes's alleged deficiencies in analysis, foresight and practical wisdom.