Pelagian

Pelagianism is the belief that original sin did not taint human nature and that mortal will is still capable of choosing good or evil without special divine aid. This theological theory is named after the British monk Pelagius (354–420 or 440), although he denied, at least at some point in his life, many of the doctrines associated with his name. Pelagius was identified as an Irishman by Saint Jerome. Pelagius taught that the human will, as created with its abilities by God, was sufficient to live a sinless life, although he believed that God's grace assisted every good work. Pelagianism has come to be identified with the view (whether taught by Pelagius or not) that human beings can earn salvation by their own efforts.

Pelagius rejected the Augustinian concept of grace. According to his opponents, Pelagius taught that moral perfection was attainable in this life without the assistance of divine grace through human free will. Augustine contradicted this by saying that perfection was impossible without grace because we are born sinners with a sinful heart and will. The Pelagians charged Augustine with departing from the accepted teaching (e.g.: John 8:11) of the Apostles and the Bible, demonstrating that the doctrine of original sin amounted to Manichaeism, which taught that the flesh was in itself sinful (and thus denied that Jesus came in the flesh). This charge would have carried added weight since contemporaries knew that Augustine had himself been a Manichaean layman before converting to Christianity. Augustine also taught that a person's salvation comes solely through a free gift, the efficacious grace of God, but that this was a gift that one had no free choice to accept or refuse.

Pelagianism was attacked in 415 at the Council of Diospolis (also known as Lydda or Lod), which found Pelagius to be orthodox. But it was later condemned in 418 at the Council of Carthage and this condemnation was ratified at the Council of Ephesus in 431. The strict moral teachings of the Pelagians were influential in southern Italy and Sicily, where they were openly preached until the death of Julian of Eclanum in 455, and in Britain until the coming of Saint Germanus of Auxerre c 429.

...
Wikipedia