In 1846, Simon Greenleaf wrote a learned tract, “The Testimony of the Evangelists,” that proved the truth of Gospels by applying the rules of evidence that govern common law trials. Greenleaf’s “Testimony” enjoys a lively internet presence among evangelical Christians today, despite Greenleaf’s nearly forgotten status among the legal profession and academics. This chapter describes Greenleaf’s manifold contributions as a founding faculty member of Harvard Law School, a rigorous law teacher, and an influential scholar whose treatise on evidence shaped nineteenth-century law. Historians, however, have mostly ignored Greenleaf’s deep commitment to evangelical Christianity. The oversight is unfortunate because Greenleaf consciously wove his evangelical beliefs into his teachings and writings, including his evidence treatise and his “Testimony,” by drawing from the core principles of the Common Sense Tradition, an evangelical mainstay. It is argued that Greenleaf’s Common Sense assumptions greatly influence current law even if their origins are unrecognized.