Fate: Condemned at the Council of Carthage (418 AD), ratified by Pope Zosimus under pressure from Augustine and the African bishops. Pelagius was exiled. Augustine’s anti-Pelagian writings shaped the entire Western theological tradition on sin and grace — including Calvin’s double predestination and the Reformation debates on justification. Semi-Pelagianism was condemned at the Second Council of Orange (529 AD).

Pelagius (~354–420 AD) was a British monk, highly respected in Rome for his ascetic discipline, who was horrified by Augustine’s prayer ‘Grant what you command, and command what you will’ — which seemed to eliminate human moral responsibility. Pelagius taught: humans have genuine free will; Adam’s sin set a bad example but did not corrupt human nature or make sin inevitable; grace consists in forgiveness of past sins, teaching, and the example of Christ; humans can choose righteousness without irresistible divine assistance. Augustine’s counter: Adam’s fall infected all humanity with original sin, corrupting the will; grace is not assistance to a free will but the replacement of a bound will; God predestines some to salvation. The stakes: Pelagius’s position implies that some people are good enough to not need Christ’s atoning death for anything other than forgiveness of individual acts. Augustine’s position implies that all humans are guilty in Adam and utterly dependent on grace — a theological anthropology with enormous consequences for all subsequent Western soteriology.

What happens when a group is declared heretical: The process is rarely sudden. It typically begins with episcopal letters condemning a teaching, escalates to synodal condemnation at a regional council, and — after Constantine — can be ratified by an ecumenical council backed by imperial authority. Once condemned: (1) Leaders are excommunicated, exiled, or — in later centuries — handed to secular authorities for execution. (2) Writings are ordered burned; possession becomes a criminal offense. Eusebius records that after Nicaea, Constantine ordered Arian books destroyed under penalty of death. The same logic applied to Gnostic texts — which is why the Nag Hammadi library was buried in a sealed jar around 367 AD, the same year Athanasius’s Easter letter listed the NT canon and ordered non-canonical books removed from churches. (3) Communities are dissolved by force where state power reaches; in regions beyond imperial reach they survive for centuries. (4) Memory is controlled — the only surviving accounts of most heresies are hostile summaries by their opponents (Irenaeus, Tertullian, Epiphanius’s Panarion), meaning we are largely reading prosecution briefs, not the groups’ own self-understanding.