There has been a recent resurgence of interest in the work of Vilfredo Pareto, one of the founders of modern economics. This book reconstructs the genesis and significance of Pareto's theory of choice which is Pareto's greatest contribution to economic science and which was used by John Hicks, amongst others, to develop microeconomics. Hicks, Allen, Samuelson and others acknowledged Pareto as the father of the new ordinalist microeconomics but at the same time, portrayed him as confused and contradictory, caught between the old and new paradigms. Luigino Bruni argues that Pareto's revolution in choice theory is better understood in the context of his own philosophical framework. This framework is revealed by reconstructing his dialogues with economists (Pantaleoni) and philosophers (Vailati and Croce), and by exploring Pareto's economic theory in the light of his philosophy of science. In addition, Luigino Bruni argues that Pareto's contribution was different and more complex than Hicks's ordinalism and Samuelson's operationalism. From this analysis emerges an image of Pareto as a man whose ideas and work was only partially fulfilled.This original and sometimes unconventional book will be of great interest to economists, historians of economic thought and philosophers of the social sciences.