A Treatise on Money, completed in 1930, was the outcome of six years of intensive work and argument with D. H. Robertson, R. G. Hawtrey and others. As in the Tract on Monetary Reform, the central concerns of the Treatise are the causes and consequences of changes in the value of money and the means of controlling such changes to increase well-being. The analysis is, however, considerably more complex and the applied statistical work much more elaborate. The Treatise has long been of interest amongst economists, as a precursor of the General Theory, as an important discussion of the mechanics of inflationary and deflationary processes and as an important statement of the problems of national autonomy in the international economy. This edition provides a new edition of the original, corrected on the basis of Keynes’s correspondence with other economists and translators. It also provides the prefaces to foreign editions.