This book presents a thorough reconstruction of the late-scholastic logical treatises De Obligationibus by the methods of modern logic and set theory. It defends the view that the treatises are intended to put forward a theory of disputation. Hajo Keffer's excellent monograph is the first full-scale treatment of the complete range of medieval treatises on Obligations, from the earliest known treatises of the mid-thirteenth century through to Paul of Pergula's tract from the early fifteenth century.