The theologian may indulge the pleasing task of describing Religion as she descended from Heaven, arrayed in her native purity. A more melancholy duty is imposed on the historian. He must discover the inevitable mixture of error and corruption which she contracted in a long residence upon earth, among a weak and degenerate race of beings.

Gibbon frames this contrast between theologian and historian in his great Enlightenment-era narrative of Christianity’s rise within the Roman world. Writing in the 1770s–1780s, he presents himself as a critical historian committed to tracing human causes—institutions, politics, passions, and contingency—rather than repeating confessional accounts of pristine origins. The sentence functions as a programmatic statement of method: the theologian may idealize religion’s heavenly descent, but the historian must examine how religious belief and practice, once embedded in society, become entangled with error, faction, and worldly power. It anticipates the skeptical, ironic tone that made The Decline and Fall controversial among contemporary clergy and apologists.

The quote asserts a sharp division between devotional narration and historical inquiry. Gibbon concedes that theology can offer an uplifting picture of religion in “native purity,” but he insists that history deals with religion as a human phenomenon—shaped by imperfect people and institutions over time. The “inevitable mixture of error and corruption” is not merely an attack on faith; it is a claim about what happens when any ideal enters social life: it becomes mediated by politics, ambition, superstition, and compromise. The passage encapsulates Gibbon’s Enlightenment skepticism and his preference for causal explanation over providential interpretation, while also signaling the melancholy cost of demystifying cherished origins.