Though the concept of natural law took center stage during the Middle Ages, the theological aspects of this august intellectual tradition have been largely forgotten by the modern church. In this book, ethicist Jean Porter shows the continuing significance of the natural law tradition for Christian ethics. Based on a careful analysis of natural law as it emerged in the medieval period, Porter's work explores several important scholastic theologians and canonists whose writings are not only worthy of study in their own right but also make important contributions to moral reflection today.