Grace, the Two Cities, and a Contested Legacy

Augustine's systematic thought grew largely out of controversy. Against the Pelagians he articulated the doctrine of original sin and the necessity of unmerited grace, arguing that the will, wounded by the Fall, cannot turn to God on its own, a position that would later divide Catholics and Protestants, both of whom claim him.

Against the Donatists he defended the catholicity of the Church and, more troublingly, the coercion of dissenters, a text later cited to justify religious compulsion. His City of God, written as Rome fell to the Goths, distinguished the earthly city from the city of God and gave medieval Christendom its philosophy of history. The Reformation's appeal to Augustine on grace, and Catholicism's on the Church and sacraments, made him the rare figure invoked as founder by traditions that anathematize one another, the clearest measure of how completely he framed the questions that followed him.