Pelagius

Pelagius was a British born monk who settled in Rome around 380 and became known there as a serious moral teacher rather than a speculative theologian; his early writings are largely practical guidance on Christian conduct. His central claim was that God, in creating human beings with free will, gave them the genuine and lasting capacity to choose good without sin, a capacity that Adam's disobedience did not remove from his descendants. On this view sin is learned through habit and bad example rather than inherited as a corrupted nature, and moral failure is a matter of the will choosing wrongly, not of a condition the will cannot overcome unaided.

Pelagius framed this as a call to responsibility: if human nature is not the culprit, believers cannot excuse their sins by blaming an inherited weakness, and must instead exert the effort God's commandments assume they are capable of. His student Caelestius pressed the position further and more provocatively than Pelagius himself is recorded as doing, arguing that Adam's sin harmed only Adam, that infants are born in the same state Adam occupied before the fall, and that infant death without baptism carries no penalty, claims that drew the earliest formal condemnation, at the Council of Carthage in 411, before Pelagius was targeted by name.

Augustine of Hippo became the chief opponent once the debate reached North Africa, arguing from Paul's Letter to the Romans and from his own account of a will too weak to reform itself without grace, recorded in his Confessions, that human nature after Adam is incapable of turning to good without a prior, freely given act of divine grace.

The controversy played out across a decade of councils rather than a single ruling. A synod at Diospolis in Palestine in 415 examined Pelagius directly and acquitted him, a verdict that provoked outrage in the West and that Augustine attributed to the bishops there not fully grasping what Pelagius meant. Two African councils at Carthage, in 416 and again in 418, condemned Pelagius and Caelestius by name, and Pope Zosimus, who had initially leaned toward clearing them, reversed course and confirmed the condemnation under pressure from the African bishops and the emperor Honorius, who followed with an imperial rescript banishing Pelagius and his followers from Rome. The Council of Ephesus condemned Pelagianism again in 431, in the same session that also condemned Nestorius.

No reliable source records where Pelagius went after his acquittal at Diospolis or how his life ended; the historical trail simply stops. The controversy outlived him. A mediating position that later theologians called semi-Pelagianism, holding that a person's will can take the first step toward faith which grace then perfects, gained support in Gaul and was itself condemned only later, at the Second Council of Orange in 529, which affirmed a modified Augustinian position as the settled teaching of the Latin church.

Modern historians distinguish Pelagius's own recorded arguments, which are comparatively measured, from the sharper claims of Caelestius and from Augustine's polemical framing of both men as a single, uniform heresy, a simplification the sources themselves do not fully support.