The two historical debates studied here are concerned with the impact of technological change on unemployment and on the economy generally. The topic is of enduring interest among both economists and the public at large. The history of these 20th century debates has not previously been studied in detail, and the book provides valuable insight into the evolution of the understanding of a fundamental issue in the economy. By providing insight into idea evolution and economic methodology, the book is a valuable description of the ways in which economists work and react to each other.