For more than thirty years Hartmut Kliemt has been one of the leading philosopher economists in Germany and worldwide. Following David Hume and the tradition of the Scottish moralists he uses the term moral science (Moralwissenschaft) to denote a unified scientific outlook on all aspects of human nature and conduct including social relationships and institutions which are to be understood as a result of individual conduct. Moral science in this sense deals with the world of human action and interaction in all its different empirical and normative dimensions; it is an approach guided by a fundamental interest in practical matters of human affairs, their troubles, shortcomings and possible betterment. As an interdisciplinary project the research programme of moral science combines scientific endeavors of philosophy, economics, politics and the social sciences in general. This volume in honor of Hartmut Kliemt includes contributions by leading scholars in this field. It illustrates the variety of subjects and problems within moral science while developing and outlining its common perspective. The first part comprises papers that examine basic issues in moral science, such as the capabilities and limits of rational agency. In the second part, the economic perspectives on human conduct are expounded. The articles in the third part exemplify the different outlooks of a moral science approach to justice and rights. Finally, in the last part, contributions from practical ethics demonstrate the scope of moral reasoning solidly based on the facts of moral practice without any metaphysical backing.