Knowing What is “Natural”: Thomas Aquinas and Luke Timothy Johnson on Romans 1–2

Over the Centuries, the first two chapters of St. Paul’s Letter to the Romans have inspired many of the most important questions faced by philosophical and theological accounts of “natural law.” For example, what is the relationship of natural law to knowledge of the God whose “eternal power and deity” have always been “clearly perceived in the things that have been made” (Rom 1:20)?¹ Similarly, on what grounds are certain actions, common in human communities, excluded as “unnatural” (Rom 1:26) and thus as opposed to natural law? And if some people “do by nature what the law requires” (Rom 2:14), then can fallen human beings obey the “natural” law without the assistance of divine grace?

This article explores such questions by comparing medieval and contemporary interpretations of Romans 1:18–32 and 2:13–16, specifically the commentaries of Thomas Aquinas and the contemporary Catholic biblical scholar Luke Timothy Johnson.² Engaging these two commentaries requires some appreciation of the differences between medieval and modern biblical exegesis. Depending upon one’s perspective, medieval exegesis may occasionally seem to stray from the text of Romans, while contemporary exegesis may occasionally seem timid in drawing out the realities that Romans depicts. My hope, however, is that a careful exposition of the various threads of Aquinas’s and Johnson’s exegeses will provide insight into the basic questions facing all natural law doctrines. This article therefore sets forth in some detail the two commentators’ remarks on Romans 1:18–32 and 2:13–16.

I. Romans 2:13–16: Knowing and Doing God’s “Law”

Thomas Aquinas

After a brief comment on the truth that only those who do the law are justified, Aquinas explores the meaning of Paul’s claim that the Gentiles “do by nature what the law requires” (Rom 2:14). Aquinas holds that the “law” in this case means the Mosaic law, but he adds some distinctions. When the Gentiles “do by nature what the law requires,” they confirm the character of the moral precepts of the Mosaic law, which according to Aquinas “flow from a dictate of natural reason.”³ Aquinas observes that the Gentiles’ ability to “do by nature what the law requires” comes from “the natural law showing them what should be done, as in Ps 4:6: ‘There are many who say, Who shows us good things! The light of thy countenance, O Lord, is signed upon us.’”⁴ The moral precepts of the Mosaic law thus belong to the natural law, which the Gentiles possess. Since the Gentiles do not possess the other precepts of the Mosaic law, however, Paul is justified is saying that the Gentiles “have not the law” (2:14).

Do the Gentiles who, according to Paul, obey the moral precepts of the Mosaic law even while being ignorant of the Mosaic law per se do so without grace? Created in the imago dei, the Gentiles share by the light of reason in the natural law, but nonetheless they cannot after the Fall fulfill this law by their natural powers. In saying that the Gentiles fulfill the law “by nature” (2:14), Paul might appear to leave room for the Pelagian heresy that without grace fallen human beings can fulfill the law of justice. Were this the case, however, Paul’s claim that “all men, both Jews and Greeks, are under the power of sin” (Rom 3:9) would make no sense. Aquinas therefore affirms that the Gentiles who successfully “do by nature what the law requires” possess “nature reformed by grace.”⁵ As examples of holy Gentiles Aquinas mentions persons before and after Christ, among them Job, who by faith already enjoyed the life of grace, and Paul’s Gentile converts, whose acceptance of the Gospel gives them, too, the supernatural life.

The holy Gentiles who do what the moral law requires, then, obey the natural law but do so by grace. In this sense, as Paul says, “they are a law to themselves” (2:14) and “what the law requires is...