Irving Fisher (1867-1947), economist, Yale University teacher, inventor, mathematician and activist reformer, was one of the most important American economists of the first half of the 20th century. On the 50th anniversary of his death in May of 1998, a large gathering of economists met at Yale to reassess Fisher's enormous scientific contribution. Such a reevaluation was facilitated by welcomed republication of all of Fisher's books and articles in 14 volumes the previous year. The offices of the Cowles Foundation at Yale University were made available for the presentations and the Cowles Foundation directors and administrators assisted with the preparation of this important volume. This book consists of original papers explaining Fisher's technical contributions to econometrics, a reassessment of his prescient and much neglected textbook on economics, his theories of capital and interest, his debt-deflation theory of depression, the various financial devices that he developed to improve governance and policy-making, and finally his eugenic crusades that included the prohibition of alcoholic beverages and healthy diets. Fisher's ideas were so advanced for his time that many of the contributors to these volumes delight in pointing out how the recent financial inventions in the world economy are catching up to the insights that Fisher provided decades earlier. This volume consists of the major papers from that conference including written versions of the comments that were pre