Despite today’s prevailing wisdom that common law and natural law are separate and distinct ideas, in reality, a centuries-long stream of American legal thought presupposed—sometimes tacitly, sometimes explicitly—that they are intertwined. Natural law, in short, undergirded the development of American jurisprudence. Contemporary debates on law, morality, and religion lack this historical memory and suffer accordingly. What the concepts meant to those who invoked them, however, requires careful delineation. We cannot generalize. The Puritans’ “natural law” was not the Revolutionaries’. Nor was the “common law” of Joseph Story, the fabled nineteenth-century jurist, altogether that of William Blackstone, its chief eighteenth-century organizer. And so, even as we recognize that American understandings of common law, natural law, and their relationship have changed, whether for good or ill, we can see that for much of American history it was assumed that common law—far from wholly detached from moral considerations—was, indeed, not just in fundamental harmony with natural law, but structured and justified by way of reference to it.