Discussion of natural law reaches a new level of sophistication in Suarez’s elaborate and careful treatment. He takes account of Aquinas, Scotus, Ockham, and their successors, and claims to defend Aquinas’ views on the main issues. Since his discussion is usually fuller than Aquinas’ discussion, and explores questions that Aquinas does not discuss at length, Suarez deserves careful study.

We may not always agree with his claim to defend Aquinas’ position. Indeed, some readers, especially among those sympathetic to Aquinas, have argued that Suarez does not simply disagree with Aquinas on some details, but radically alters Aquinas’ views on natural law and the foundations of ethics, and alters them for the worse. This departure from Aquinas is historically significant because—it is suggested—Suarez strongly influences the theory of natural law that has been prominent in post-Reformation Roman Catholic moral theology. Historians of ethics and political theory have concentrated on Suarez’s treatment of law, and especially of natural law. His treatise ‘On Laws and God the Legislator’ clarifies many issues that his predecessors pass over. Aquinas has relatively little to say on the relation of the principles of natural law to the will of God. Some of his successors, particularly Scotus and Ockham, have more to say. Suarez sets out and discusses in full the major issues that arise in his predecessors; he considers how many separable claims can be made, and what follows from each of them. Since Grotius and Cudworth are probably familiar with Suarez’s discussion, it provides a useful basis for comparing modern with mediaeval views.