More than any other Reformer, John Calvin is appealed to for his insight on natural law. This is probably due to the stubborn persistence among scholars to single him out as the chief early codifier of Protestant doctrine. While this approach is understandable given the force of habit, the discussion should be widened beyond Calvin to include those Reformers who either preceded him or were contemporaries of his and the later representatives of Protestant orthodoxy.

Though Calvin talks a fair bit about natural law, his treatment of it is unsystematic and imprecise compared to the medievals and some of his contemporaries. Susan Schreiner, a Calvin expert and University of Chicago Divinity School professor, thinks Calvin's discussion of natural law should be seen as an extension of his doctrine of providence. In her view, Calvin uses natural law for the practical purpose of explaining how order is preserved after the fall in society, law, and morality.

As time passes in the sixteenth century, however, Protestant theologians develop increasingly sophisticated doctrines of natural law that they situate in the wider context of the grand moral tradition with Aristotle, Cicero, Augustine, Aquinas, Scotus, and many others. What is striking here is the degree to which Peter Martyr Vermigli and his fellow Reformer and former student Jerome Zanchi, for example, show continuity with Thomas and Scotus.

The astonishing thing about the rise of Reformed scholasticism in the 1540s and 1550s is that its medieval roots run heavily to Thomism and Scotism, hardly at all to nominalism. This challenges the opinion of several prominent contemporary Roman Catholic and Protestant intellectuals, who credit the emphasis on the will in Protestant ethics to the influence of William of Occam rather than to medieval Augustinian antecedents.

Use of traditional natural-law terms in sixteenth- and seventeenth-century Protestant orthodoxy show significant points of continuity with the thought of Thomas and Scotus. The discontinuities stem from disputes over the interpretation of key biblical passages, an expanded sense of how sin affects reason and human nature, and a criticism of works righteousness, to mention a few key areas. Calvin, Martyr, and the Reformed scholastics all share the conviction that Scripture is the cognitive foundation of theology and that moral arguments can be based on precepts drawn from that foundation.

I want to point to four doctrines where natural law exerts some influence.

First, it is important to recognize that none of the confessional documents of the magisterial Reformation — whether Lutheran or Reformed — rejected the doctrine of natural law. In fact, those documents universally state that Gentiles — though outsiders to God's special revelation to Israel in the law and the prophets — remain accountable to the moral law by means of the natural knowledge of God's will experienced in creation, conscience, and reason. Confessional examples abound to prove this point, but I will mention only what the Second Helvetic Confession (1566) states:

We teach that the will of God is set down unto us in the law of God; to wit, what He would have us to do, or not to do, what is good and just, or what is evil and unjust. We therefore confess that 'the law is holy . . . and good'; and that this law is, by the finger of God, either written in the hearts of men, and so is called the law of nature, or engraven in the two tables of stone, and more largely expounded in the books of Moses.

This confession, like so many other sixteenth-century confessions, makes an explicit identification of the law written on the heart in Romans 2 with the natural law.

Second, natural law played a significant role in the three uses of law articulated by the Reformers. The first use of law is to convict of sin by taking away all natural presumption of righteousness. The Reformers made frequent appeal to the conscience's imprinted knowledge of right and wrong in this respect. The second use of law is to maintain order. “Since the devil reigns in the whole world,” states Luther, “God has ordained magistrates, parents, teachers, laws, shackles, and all civic ordinances to at least bind his hands and keep him from raging at will.” The third use of law is to exhort believers to ongoing obedience and gratitude. “The law is to the flesh,” says Calvin, “like a whip to an idle and balky ass, to arouse it to work. Even for a spiritual man not yet free of the weight of the flesh the law remains a constant sting that will not let him stand still.”

Third, while the Reformers famously emphasized Scripture as the ultimate authority for doctrine and Christian living, the modern doctrine of sola scriptura falsely pits the Reformers against the Scholastics on the issue of tradition. Unlike modern Protestants, the Reformers did not pit Scripture and tradition against each other as antithetical sources of authority, even though they did affirm the normative priority of Scripture in theology and ethics. The Reformers also did not play special revelation off against general revelation, as tends to happen today, both were considered legitimate forms of revelation that served distinct roles in theology. This is why the modern Protestant rejection of natural law in favor of supernaturally revealed legal or moral instruction is skewed in relation to the thought of the Reformers.

Fourth, the Reformers felt no tension in affirming a strong doctrine of original sin, on the one hand, and natural law, on the other. While every aspect of reality was affected in the fall, including the rational and social nature of human beings, the Reformers did not believe the divine image was totally annihilated. Instead, only aspects of the image were destroyed while other aspects were permanently disoriented. That disorientation put people in a wrong relationship with God, their neighbors, and the world. However, the implanted knowledge of right and wrong, which survived the fall as a relic of the original image, was now weakened and obscured. The Canons of Dort , a doctrinal standard issued by the Synod of Dort (1618-19), for example, affirms the existence of natural law but also points to its insufficiency:

There remain in man since the fall, the glimmerings of natural light, whereby he retains some knowledge of God, of natural things, and of the difference between good and evil, and shows some regard for virtue and for good outward behavior. But so far is this light of nature from being sufficient to bring him to a saving knowledge of God and to true conversion that he is incapable of using it aright even in things natural and civil.

Without this affirmation of the natural knowledge of God, the result for ethics would be pessimism toward any transcultural, universal moral ontology. The alternative, then, would be to place ethics exclusively within the sphere of redemption and the new creation. If those “glimmerings of natural light” were wiped out, it would be difficult to find a bridge to the public sphere in which Christians and non-Christians could work side by side.