Beneath the common Protestant Christianity professed by North and South, a chasm widened not only in constitutional interpretation and vision of social order but in theology. During the seventeenth and eighteenth centuries, acrimonious debate shook the long-standing pillars of Christian belief: authority of Scripture; Revelation; the divinity of Jesus; the afterlife; the very existence of God. By the nineteenth century the doctrines of original sin, human depravity, the Trinity, and much else were receding in Western Europe and in the northern states of the American Union, where the social relations of transatlantic capitalism shook the ground on which Christian orthodoxy and a conservative world view could be sustained. In the South, however, slavery permitted them to flourish. Before the War and beyond, the South resisted the principal theological and philosophical tendencies of the age, and the southern churches, Arminian and Calvinist, stood firm for orthodoxy. Flannery O'Connor, explaining the difference between twentieth-century Northerners and Southerners, suggested that a great many more Southerners than Northerners still believe in original sin.

Demotion of Jesus from Second Person of the Trinity to a moral philosopher became fashionable in the late eighteenth century, enlisting the talents of Thomas Jefferson, Benjamin Franklin, and Joseph Priestley among those who sought to disentangle the “mythical” from the “real” Jesus. Bishop Meade recalled that Episcopalian preaching in Virginia at the beginning of the nineteenth century had been substituting morality for religion, as English clergymen took their texts less from Scripture than from Plato, Cicero, and Epictetus.