Until quite recently, natural law thinking had been a Catholic preserve. My interest in it was awakened during my days as a Jewish undergraduate at the University of Chicago, by the great Leo Strauss—himself a serious, though nonobservant, Jew. When I told Strauss of my interest in natural law, he told me, “I am not a natural law thinker,” and suggested I study with Yves Simon, a devout Catholic. Later, as a graduate student in philosophy, having received my rabbinical ordination, I went to Georgetown University to study under the Catholic natural law theorist Heinrich Albert Rommen.
It is understandable that many Catholics have been active in natural law discourse and advocacy, for one might say that natural law theory is the Catholic tradition’s most consistent exercise of practical reason. Of course, Catholics must admit that non-Catholics like me may also be natural law philosophers, because natural law presents itself as philosophy, and philosophy necessarily claims to be universal. In fact, most Catholic philosophers have welcomed non-Catholics like me into the natural law enterprise, in which they don’t wish to be alone. Because of this welcome from the earlier shareholders, modern natural law is a truly interreligious enterprise. It includes Jews, Protestants, and, most recently, Muslims.
But if natural law discourse and advocacy are pursued only by members of the three “Abrahamic” religions—Judaism, Christianity, and Islam—the question arises: Must one be religious in order to be a natural law advocate? The fact that natural law is an interreligious or interfaith enterprise does not necessarily imply its universal rationality. Indeed, isn’t it likely that advocacy of natural law arises from theological reasons, and is thus limited by them? Just as the Catholic magisterium could be seen as teaching a universally applicable morality, prescribed by its own revelation-based authority, so too the Jewish tradition’s teaching of a universally applicable morality could be seen as issuing from its revelation-based authority. In this view, then, natural law is universal only in its application; in its conception, it remains particularistic. What is universally binding is represented to the world as stemming from God’s particularly authoritative will rather than from his universally persuasive wisdom.