The Prologue to Bishop Ivo of Chartres' Decretum and Panormia has long been recognized as a seminal text in medieval canon law. It can be fairly called the first extended treatment of ecclesiastical jurisprudence. In its attention to categories of law and context, it also demonstrates the nascent scholastic method. This treatise on the tension between rigor and mercy in judgment - and how they could be reconciled through dispensation - spoke not only to legal and theological concerns of the early twelfth century but also to enduring questions about the nature and limits of ecclesiastical law. This study offers the first critical edition of the text based not only on extensive examination of the manuscripts but also the sources Ivo used in its composition. This enables a detailed examination of the text, which, from start to finish, reveals Ivo's conviction that love, caritas, was the essence of canon law.