St. Thomas Aquinas’s “De Regno” (one of the “other” works in addition to the Summa) is often translated, “On Kingship,” and at other times, “On Government.” The former is somewhat incomplete because it sounds as if the treatise is about monarchical arrangements alone. It is, of course, true that Aquinas defends monarchy in De Regno (the treatise was written to advise the King of Cyprus), but he does so within a broader exploration of the nature of political governance and the more general problem of tyrannical government (to include tyranny by the many, and not only by the one). “On Government” might be acceptable if “government” is taken to mean “politics” in the broadest sense as the “common thing” or fundamental commitments of the community.

Maybe the most accurate translation would be something like, “On the Political Establishment,” just in the way that our own Constitution talks about “establishments” in the First Amendment when it proscribes establishments “of religion.” One might wonder just which sort of establishments are permitted, or even encouraged, under such an arrangement. But back to Aquinas: the more expressly theological features of De Regno also incorporate a view of church-state relations that one might call mutually supportive or, more controversially, integrated, blending Christian and classical themes and arguments (as is usual for Aquinas). And there is much of interest as respects what we call “civil religion” and its dangers in De Regno.

Here is a relatively new book emphasizing the church-state issues in this important work: The Christian Structure of Politics: On the De Regno of Thomas Aquinas (Catholic University of America Press), by William McCormick, SJ (with a new paperback out next spring).

The Christian Structure of Politics, the first full-length monograph on Thomas Aquinas’s De Regno in decades, offers an authoritative interpretation of De Regno as a contribution to our understanding of Aquinas’s politics, particularly on the relationship between Church and State. William McCormick argues that Aquinas takes up a via media between Augustine and Aristotle in De Regno, invoking human nature to ground politics as rational, but also Christian principles to limit politics because of both sin and the supernatural end of man beyond politics. Where others have seen disjoined sections on the best regime, tyranny, and the reward of the king, McCormick identifies a dialogical structure to the text – one not unlike the disputed question format – whereby Aquinas both tempers expectations for the best government and offers a spiritual diagnosis of tyranny, culminating in a sharp critique of civil religion and political theology.

McCormick draws upon historical research on Aquinas’ context, especially that of Anthony Black, Cary Nederman and Francis Oakley, from which he develops three themes: the medieval preponderance of kingship and royal ideology; the relationship between Church and State; and the intersection of Latin Christianity and Greco-Roman antiquity. While age-old concerns, recent research in these areas has allowed us to move beyond simplistic platitudes.

For scholars of political theory and the history of political thought, De Regno will prove fascinating for the interplay of Aristotelian and Augustinian elements, undercutting the conventional wisdom that Aquinas was simply an Aristotelian. De Regno also includes an extended treatment of civil religion, one of Aquinas’ most historically-oriented discussions of politics.