One thinker had an especially strong role in shaping Christian views about sexual activity and many other issues: Saint Augustine of Hippo (354–430), the most influential church father in the West. Augustine was born into an urban family in what is now Algeria in North Africa. His father, a minor civil servant, was a pagan; his mother, Monica, was a devout Christian. He gained an excellent education, fathered a son, and experimented with various religious ideas. In adulthood he converted to his mother’s religion, eventually becoming bishop of the city of Hippo Regius. Augustine gained renown as a preacher, a vigorous defender of orthodox Christianity, and the author of more than ninety-three books and treatises.

Augustine’s autobiography, The Confessions, is a literary masterpiece and one of the most influential books in Western history. Written in the rhetorical style and language of late Roman antiquity, it marks a synthesis of Greco-Roman forms and Christian thought. The Confessions describes Augustine’s moral struggle, the conflict between his spiritual aspirations and his sensual self. Many Greek and Roman philosophers had taught that knowledge would lead to virtue. Augustine came to reject this idea, claiming that people do not always act on the basis of rational knowledge. Instead the basic or dynamic force in any individual is the will. When Adam ate the fruit forbidden by God in the Garden of Eden (Genesis 3:6), he committed the “original sin” and corrupted the will, wrote Augustine. Adam’s sin did not simply remain his own but was passed on to all later humans through sexual intercourse; even infants were tainted. Original sin thus became a common social stain, in Augustine’s opinion, transmitted by sexual desire. By viewing sexual desire as the result of Adam and Eve’s disobedience to divine instructions, Augustine linked sexuality even more clearly with sin than had earlier church fathers. According to Augustine, because Adam disobeyed God, all human beings have an innate tendency to sin: their will is weak. But Augustine held that God restores the strength of the will through grace, which is transmitted in certain rituals that the church defined as sacraments. Augustine’s ideas on sin, grace, and redemption became the foundation of all subsequent Western Christian theology, Protestant as well as Catholic.