The economic model of behaviour is fundamental not only in economic theory, but also in modern approaches of other social sciences, above all in political science and law. This book provides a comprehensive treatise of the general model, its philosophical and methodological foundations and its applications in different fields. In addition to the basic model, extensions to its assumptions are examined to account for complex applications like low-cost situations with moral behaviour. Finally, the book takes a broader perspective by evaluating the impact of the model on economic policy and on the development of the field of social science as a whole, such as the competition between individualistic and collectivist approaches.