Over the past several years, Brian McCall has brought his considerable legal and historical expertise to bear on such issues as the foundations and authority of law, the status of common law, and the moral legitimacy, or otherwise, of financial instruments such as secured credit. He is well known for his forthright and sometimes controversial views on Christian beliefs and practices, contemporary society, and the law, and he has proven his willingness to revive unpopular views from the past, for example, in a spirited defense of the medieval condemnation of usury. In The Architecture of Law, McCall brings together and expands upon the diverse strands of his work so far, setting out a comprehensive natural law jurisprudence grounded in classical figures (Cicero, medieval jurists, and, especially, Aquinas) and developed in conversation with well-known legal philosophers (H. L. A. Hart, Joseph Raz, John Finnis). In the process of doing so, he demonstrates the vitality and surprising relevance of the natural law, as understood by the (mostly) medieval jurists and theologians whom he engages.

In setting out his theory of the natural law, McCall draws on the metaphor of a building—hence, the title of the book—in order to express what he takes to be the structure of natural law reasoning. The natural law, he argues, rests on the foundation of the eternal law, which is the basis for both the substantive content and the authoritative force of moral and legal reasoning. The natural law itself corresponds to the walls of the structure that rest on this foundation, and human laws are the decorations on these bare walls. Human builders are, at best, fallible, and so the Architect has provided an instruction manual, in the form of divine, that is to say scriptural law, which supplements and where necessary corrects human reasoning. Finally, this building project needs a foreman to coordinate the efforts of the workers, and so McCall devotes a chapter to the source and limits of the authority of the lawgiver.

Setting aside the trope of law as building, how do these elements of moral and legal reasoning operate? On McCall's account, the eternal law is nothing other than God's own providential wisdom, through which he creates and governs the universe. As such, the eternal law contains, as it were, the ideal types of every kind of creature that exists, and every creature operates in such a way as to strive toward the attainment of that perfect ideal. In the human creature, this striving toward a specific ideal is carried out through deliberate, reasoned actions directed toward the attainment of fulfillment or happiness, in accordance with each person's best understanding of the human good. As Aquinas would express it, the natural law is the rational creature's participation in the eternal law, mediated through the first principle of practical reason, “good ought to be done and evil ought to be avoided” (102) as habitually known through synderesis.

This first principle is also identified with the first principle of natural law, but of course, as it stands, it is too abstract to provide actual moral or (much less) legal guidance. Further guidance is supplied through innate inclinations toward those goods that are constitutively bound up with the ideal of human existence contained in the eternal law, such as life, community, and knowledge of the truth. Through these inclinations, which must be discerned through reasoning as well as experience, we come to see that certain aims are worthy of pursuit, and certain kinds of actions which frustrate the attainment or possession of these goods are prohibited. For example, we recognize a duty to pursue the truth, and we recognize that murder, which destroys life, is prohibited. At this level of specificity, we move from first principles to what McCall describes as the primary precepts of the natural law, for example, “Pursue truth,” or “Do not kill” (149). McCall goes on to argue that human lawmakers generate legal enactments from the natural law through processes of determination, through which natural law precepts are formulated in a specific way for a particular community. Human law is necessary and legitimate because the natural law as such leaves open an indeterminate range of options for attaining the end of human perfection toward which it is developed. Lawgivers, who are charged with the care of the common good, have the task of specifying how the natural law is to be carried out in a given community. Of course, some laws follow more or less directly from the natural law, for example, the laws prohibiting murder. But even when human laws appear to be arbitrary—for example, traffic regulations—they carry the force of the natural law, as authoritative specifications of general precepts.

McCall is well aware that the processes of reason and lawmaking through which we move from the precepts of the natural law to specific legal enactments are by no means straightforward. He acknowledges the intrinsic indeterminacy of the natural law, and he recognizes that for this reason, if no other, we cannot treat the natural law as a full-fledged legal code (291–92). Granting all this, what role does the natural law play in legal theory? Most fundamentally, this account of natural law offers a foundational theory of legal authority, which on this view runs through natural law to God's own eternal law. It also offers what we might describe as a realist ontology of laws, which on this view are specifications or derivations of an objective natural law, rather than being the products of human fiat. And even though McCall does not treat the natural law as a legal code, he does seem to give it a kind of legal standing in some circumstances.

One advantage of a natural law jurisprudence, as McCall presents it, is that it offers an alternative to our current way of understanding the law as a set of enactments, brought into being through legislative fiat, and interpreted through painstaking attention to the meanings of written texts. McCall does not deny the necessity for lawmaking authority, or the legitimate place for written laws. However, he argues forcefully that any attempt to build a system of laws on the basis of formal enactments alone will lead to a superabundance of statutes, generating many problems of interpretation and application. In contrast, an approach to lawmaking informed by a sound understanding of natural law will have the resources to avoid these difficulties. McCall's key point here is that the natural law, in the form of collective moral reasoning and the formation of practices, operates throughout the community—and correlatively, a legal system can acknowledge the legal force of collective judgments, as expressed through long-standing traditions and current customs. By doing so, the lawgiver places him or herself in a position to take advantage of the rich situational contexts of meaning that inform the community in formulating and promulgating laws. Seen within the context of Anglo-American jurisprudence, this approach would lead to a renewed appreciation of the common law, and a turn away from the current focus on texts and original meanings in judicial interpretation. McCall's defenses of common law, customary law, and the historical traditions associated with the “law of nations” are among the highlights of this book, offering fresh perspectives on the unexpected ways in which the natural law can be legally relevant, without being accorded the status of formal statutes.

Defenders of the natural law have traditionally held that the natural law is legally significant in another way, insofar as (supposed) laws that violate the natural law are held to be invalid. This is McCall's view, as well. He is well aware of the complex issues raised by this claim, and his defense is carefully qualified to take account of these complexities. He distinguishes between laws that are simply bad (for example, imprudent) and laws that are truly unjust because they are not directed to the common good or violate some principle of natural law (369). Faced with a law that is genuinely unjust, the conscientious individual may be obliged to refuse to obey it, if it commands something clearly contrary to the natural law. If that is not the case, she may be permitted or even obliged to obey it, for the sake of public peace or even personal safety. McCall goes on to consider the implications of this line of analysis for judicial review, as it operates in the United States and other similar legal systems. Judicial review as practiced in this system presupposes a division of legal labor—the legislature enacts the law, whereas the judge interprets the enacted law, applying criteria derived from a comprehensive system of laws and legal principles. The relevant point is that the judge is not supposed to evaluate laws on the basis of extrajudicial principles, and so presumably she should not refuse to enforce a law on the grounds of its injustice or general morality.

McCall, however, insists that in some circumstances, at least, a judge is obliged to refuse to enforce an unjust (putative) law. In this case, the judge acts in accordance with the natural law, which is itself a real law: “a judge does not declare a purported human law invalid on the basis of personal moral norms. . . . A judge in such a position could refuse to enforce a purported human law because in fact the utterance is not a legal law. Likewise, a judge refusing to enforce a state statute on the grounds that it has been preempted by a federal statute is not using personal morality to invalidate a law. The judge is resolving a conflict between two purported statements of law by recourse to the higher law” (367).

This is a remarkable claim. It appears that in some kinds of cases, the natural law does have direct legal standing, insofar as a judge is permitted—even obliged—to base a legal opinion on an appeal to the natural law. This claim raises fundamental questions, about the suitability of the natural law as a legal standard, and about the legitimacy of appeals to the natural law in judicial contexts. McCall follows his sources in identifying the natural law most fundamentally with general principles. As such, it must be applied and specified in order to yield concrete practical guidance. But if that is so, then the comparison between the natural law and state statutes would seem to be misleading. State statutes are, for better or worse, fairly detailed documents, and while they can of course be badly formulated, more often than not, the reader generally knows what they mean. The principles of the natural law are general and indeterminate, and as such open to a wide range of conflicting interpretations. This brings us back to questions of authority: it is possible to defend a natural law jurisprudence, while also acknowledging that not everyone shares equally in the authority to interpret and apply the natural law. There are, perhaps, good reasons to defend a division between legislative and judicial authority, even within a natural law jurisprudence.

Of course, McCall recognizes that the natural law needs to be interpreted in order to be applied, and he acknowledges that the interpretative process is subject to error, especially given the miasma of moral failings that cloud our judgments. For this very reason, he gives a central role to divine law, that is to say, scripture, as a corrective to our judgments about the natural law. As such, he seems to hold that scripture itself has legal standing, at least in some circumstances: “at least in extreme cases, human laws, of whatever origin, that compel a violation of the revealed divine law are not laws at all and must be refused” (238–39). Clearly, this approach would not be compatible with fundamental principles of the legal system in the United States and many other nations. This incompatibility, in itself, need not worry McCall. He might well reply, “so much the worse for the US legal system,” and propose his robustly theistic natural law jurisprudence as an alternative. At that point, the emerging debate would focus on the competing claims of contemporary liberalism and McCall's theistic jurisprudence. There is a moral case to be made for secular liberalism, and in order to advance his project, McCall would have to address it—perhaps a project for another book?

At any rate, McCall's appeal to divine law raises a more fundamental set of questions. Divine law, as he notes, is God's law as revealed in scripture (420). McCall's natural law jurisprudence presupposes that scripture will provide clear and definite guidelines to follow when our judgments of natural law are uncertain. But as an examination of scriptural texts makes plain, scripture is very far from offering a set of perspicuous moral guidelines. A significant number of scriptural precepts are clearly dated or otherwise inapplicable to our lives today, for example, the laws pertaining to sacrifice; correlatively, scripture has nothing to say about many questions of urgent concern today, for example, abortion or climate change. Some scriptural precepts are, on their face, morally repugnant, for example, God's command to Israel to wipe out the entire population of the promised land (Deuteronomy 20.1–20), or the many precepts which presuppose, regulate, and reinforce slavery. In addition, there are a number of well-known tensions, if not outright contradictions, among different scriptural precepts. These difficulties have been recognized since late antiquity. Since the late nineteenth century, theologians have faced the further challenge of reconciling the status of scriptural texts as revelation with the clear evidence of their human origins. None of this necessarily implies that scripture is not revealed, or in some way a mediator of divine revelation. But these challenges would have to be addressed in order for divine law to play the role that it does in McCall's overall system. Again, this is perhaps a topic for another book.

At any rate, while looking forward to further engagement with these issues, we should be grateful for the book that McCall has written—a bold, thoughtful, and cogent defense of classical natural law theory and its relevance for the contemporary theory and practice of law. This book deserves wide attention from legal scholars as well as theologians and historians of law.