The primary aim of the book is to provide a critical evaluation of the origin and development of the Cambridge saving-investment analysis. This work disentangles painstakingly from a maze of sometimes contradictory, obscure and often neglected contributions, the line which leads from Marshall's interest theory to Keynes's income adjustment process. In particular, it charts, for the first time, the various steps taken by this line of inquiry in the writings of Pigou, Hawtrey, Robertson, Lavington and Keynes.