The Great Depression of the 1930s with its dramatic unemployment rates was one of the most striking economic events of the past century. It shook economists' belief in the existence of self-adjusting forces and prompted Keynes to write his masterwork, The General Theory of Employment, Interest and Money (1936). This book studies the evolution of macroeconomics viewed through the window of involuntary unemployment. Involuntary unemployment has played a central role in the development of macroeconomics and has also been the object of heated debates, being defended and attacked by prominent economists with equal vehemence. However, this concept has gradually disappeared from textbooks and research. This book recounts and ponders this demise, asking is this a manifestation of a defect of economic theory or is it rather that the involuntary unemployment concept is of little use when it comes to economic theory? In order to disentangle these issues, the author critically examines the different explnations of involuntary unemployment that have been offered from Keynes up to the end of the 1980's. After a consideration of the General Theory , the author studies the the works of pioneering ÍNDICE Chapter 1: Introduction Part 1: Conceptual Prerequisites Chapter 2: Defining Involuntary Unemployment Chapter 3: From Labour Rationing to (Involuntary) Unemployment Chapter 4: Trade Organisation Part II: Involuntary Unemployment in Keynes' General Theory Chapter 5: Keynes' Programme. A Reconstruction Chapter 6: Involuntary Unemployment in Keynes' General Theory Part III: LM Macroeconomics Chapter 7: Hicks Mr Keynes and the Classics Chapter 8: IS-LM a la Modigliani Chapter 9: Lange, Leontief, Tobin, Klein and Hansen Chapter 10: Involuntary Unemployment in Macroeconomic Textbooks Part IV: Reconstructing Keynesian Economics: the Disequilibrium Approach Chapter 11: The Forerunners: Patinkin, Clower, Leijonhufvud Chapter 12: The Second Generation: Barro and Grossman, Dreze, Benassy and M