Protestant Christianity strongly influenced the development of the political and constitutional history of the United States, from the nation’s very beginnings in colonial times up to the great civil rights movements of the twentieth century. Protestant Christians like Martin Luther King, Jr. have even invoked natural law to defend justice in the public square. As Dr. Charles points out, however, many Protestants today consciously reject the natural law tradition because it admits that humanity can know the universal moral law without a special revelation from God. Dr. Charles devotes his essay to showing that in fact the founders of the Protestant movement—Martin Luther, Philip Melanchthon, John Calvin, and Huldreich Zwingli—firmly asserted the existence of a law of nature, knowable by reason without the gift of faith. By and large, he shows, the Reformers were in continuity with the natural law tradition that preceded them and largely agreed with Catholics on this point. Charles goes into greater depth about the distinctions among the Reformers in their teaching about the law of nature, or as they also called it, following St. Paul’s Letter to the Romans, “the law written on the heart.”