This is a book about Keynes's theory or theories. As such, it is inevitably a work in the history of economic thought, a study of past ideas. But, perhaps more than most studies of the past, my aim is to revive interest in some of Keynes's ideas, and the vision behind them, that have been neglected. Other ideas, less important and, I believe, less faithful to Keynes's vision, have come to be regarded as Keynes's intellectual heritage.

I began this work, inadvertently, more than twenty years ago. Students in my graduate macroeconomics course lacked an understanding of the classical problems that macroeconomists address, or so I thought. One way to let them learn about the problems was to see them through the eyes of the great economists who had posed them, often in the context of their own time. Economists such as Thornton, Wicksell, Fisher, and Keynes had laid out some of the problems without always finding a solution. Problems such as the reason for unemployment, the nature and role of money, the role of the money-credit system, and inflation remain on economists’ active research agenda. The great and generally helpful increase in the degree of abstraction and in the technical skills that economists now bring to these problems had the effect, at times, of obscuring rather than clarifying the nature of the problems. A few classes on the past seemed to me time well spent before turning to models and recent developments.