some four thousand different texts and authoritative dicta, the so-called Decretum Gratiani formed the first part of what eventually became the Corpis iuris canonici (the Code of Canon law). Gratian’s work was a conduit for legal, philosophical, and theological opinions about natural law as well as for many other legal subjects. His method of reconciling, or harmonizing, diverse opinions became a model for the golden age of scholasticism in the schools of the thirteenth century.
About fifteen years later (circa 1155), Peter Lombard adopted a similar method in treating theological opinions in Sententiarum libri quatuor, and as a young student in Paris a generation later, Thomas Aquinas studied and wrote a commentary on the four books of the “Sentences of Lombard.” Thomas’s unfinished Summa theologiae, which he composed off and on for more than a decade in Paris and Italy during the mid-thirteenth century, is widely regarded as the most masterful expression of medieval scholasticism. This is because Thomas set out not only to harmonize nearly a millennium of theological opinions but also to treat the “new” learning of the recently recovered pagan philosophers, especially Aristotle.
Though he was well aware of the emerging legal systems of both civil and canon law, Thomas was not professionally trained in the laws. He was, instead, a Dominican theologian. In all his writings there is but one discussion of law for its own sake; this is found in the prima-secundae (I-II) of the Summa theologiae, questions 90 through 108. Most of this so-called “Treatise on Law” examines human and divine positive law as well as the lex nova, or “New Law,” of the Gospel. It is perhaps paradoxical that while Thomas’s treatment of natural law is by far the most influential and certainly the most quoted discussion of the subject in the history of philosophy, Thomas himself had relatively little to say about natural law. Whereas his Summa theologiae consists of more than five hundred discrete questions, only one is devoted exclusively to the lex naturalis.22
In this case, however, quantity is misleading; for in terms of the clarity of its analysis and exposition, the synthesis of materials (legal, theological, philosophical, political), and the deft application of natural law to disputed issues of human conduct (just war, theft, polygamy, etc.), Thomas’s work in this area was a significant achievement. It is written serenely and in a manner that a modern reader might regard as understated, but it is all the same a tour de force. It outlived its immediate medieval context and the various “Thomisms” that have evolved in the intervening centuries.
Thomas’s natural law theory had its greatest influence long after the Middle Ages. During the period of late scholasticism (roughly, the sixteenth and seventeenth centuries) Dominican and Jesuit theologians resurrected Thomas in order to respond both to the Reformation and to a series of international political crises. These crises were brought about by new and potent expressions of royal absolutism on the part of Protestant and Catholic sovereigns and by moral and political conflicts ignited by their colonial policies in the New World. In a period of civil wars and domestic disturbance, theories of royal absolutism were geared to enhance executive power. It is the recurrent story of natural law theory that it crops up precisely when the political order removes barriers to legislative and executive will.
Such is what happened during the Baroque era, where these issues were debated in the seminaries and in the courts of the Hapsburgs. Two centuries before the American Revolution, and nearly three centuries before the American Civil War, issues of political self-determination and slavery were debated in terms framed by Thomistic natural law theory. For example, the Dominican theologian Francisco Vitoria argued successfully for the natural rights of native peoples in the Indies and developed exacting criteria for the use of war by nations. His lectures, called the Relectiones (1527–40), influenced Hugo Grotius and the emerging modern jurisprudence of international law. Another Spanish Dominican, Bartolomé De Las Casas, whose Historia de las Indias (1561) was translated into several languages, worked and wrote tirelessly for the natural rights of Indians to political liberty and property. Consequently, the transition from medieval doctrines of natural law to modern conceptions of natural rights was achieved in no small part by Spanish scholastics.23
The best known of the late scholastics was the Spaniard Francisco Suérez (1548–1617), whose De Legibus ac Deo Legislatore (1612) was the most ambitious effort in the modern period to construct a Thomistic legal theory. Noteworthy for our purposes is that Rommen’s first book, Die Staatslehre des Franz Suarez (1927), was on Suárez, and there are repeated references to the Spanish Jesuit in The Natural Law. It was Suárez who vigorously defended the legality of natural law, which he applied to problems of political consent, just war, and right of revolution against unjust political authority. His emphasis upon the divine ground of natural law, and his critical application of it against the exaggerated imperial power of temporal sovereigns suggests that Suárez is more deserving of the title “father of modern natural law” than merely to be known as a “late” interpreter of Aquinas. Indeed, Suárezian natural law exerted considerable influence on both Catholic and Protestant legal and political theorists. That during the Second World War the Carnegie Endowment for International Peace published a Latin-English edition of Suárez’s De Legibus is but one measure of his continuing influence.
More immediately, Rommen and his fellow Catholic thinkers were the products of a new wave of scholasticism that can be traced to Pope Leo XIII’s encyclical Aeterni Patris (1878). Leo called for a return to the primary sources of scholastic philosophy, especially to Thomas Aquinas. Whereas “late scholasticism” was bred primarily in Roman and Spanish seminaries, the “neo-Thomism” prompted by the Leonine reform was led by lay scholars, many of whom taught in secular universities.
Neo-Thomism was marked by two main traits. The first was scholarly attention to original texts, which in turn led to fresh interpretations of the premodern natural law traditions. The second, and somewhat opposite tendency, was a lively interest in making the old traditions relevant to contemporary political and legal problems. Indeed, it was the combination of the two that made neo-Thomism the most creative period of scholasticism, which flourished in the absence of anything resembling the medieval schools.
Papal encyclical letters became another significant transmitter of the scholastic tradition by setting forth in brief form the principles that ought to apply to controverted issues of social, political, and economic policy. Rommen was imprisoned by the Nazis precisely because of his efforts in behalf of just such encyclical teachings. Pope Leo XIII himself issued more than eighty such encyclicals that addressed social issues such as the rights of workers and church-states relations, as well as more philosophical questions such as the origin of political authority. As Europe moved through the crises of the First World War, the Depression, the rise of Fascism, and the Second World War and its aftermath, the encyclicals became an increasingly important source of Catholic thinking on political matters.
Two points need to be made about the social encyclicals. The first is that these encyclicals produced an extensive body of applied natural law on issues both great and small, from the problem of socialism and rights of private property to the morality of dueling. The second point is the more important one for understanding Rommen’s work. The encyclicals provided a model for integrating two philosophical perspectives that had not been successfully unified in scholastic natural law doctrines. On one hand, the encyclicals were “conservative” on the intellectual grounding of natural law and quite traditional on particular matters of moral conduct; on the other hand, they were operationally “liberal” on many of the great political questions of modernity. For example, they favored the principle of subsidiarity against the practically unlimited powers of modern states; they supported the people’s right to select the particular form of government; they upheld the rights of individuals to organize into labor unions, to hold property, and to enjoy religious liberties.
Rommen, Maritain, Simon, and John Courtney Murray certainly shared the conviction that a traditional metaphysics of natural law could be expounded without its having to adopt an antimodernist stand on political institutions. As Rommen put the question in The State in Catholic Thought, the perennial philosophy must eschew the romantic reaction against modernity, a reaction that led many Catholic apologists of the
