In what has universally been recognized as a classic of institutional economics, John R. Commons combined the skills of a professional economist, the sensibilities of an American historian, and the passion of an active participant in the conflicts of individuals, self-interest of groups, and function of voluntary associations. The aim of this volume is to work out an evolutionary and behavioral theory of value. In order to do so thoroughly, Commons examines the decisions of the courts. Doing so compelled an examination of what the courts mean by reasonable value. Commons found that the answer was tied up with a notion of reasonable conduct. It was Commons who carried the study of the habits and customs of social life to the next stage: the decisions of the courts that are based on custom and that profoundly impact the nature and function of the economic system as such.