For several decades before the doctrine of sin was fully worked out by the Roman Catholic Church, this teaching brought both of them into numerous theological disputes about the nature of sin with several Christian leaders in the church.
Among them were the Bishop of the northern African Roman province of Hippo, Augustine, (later known as "Saint Augustine,") and the theologian Jerome. Augustine especially did more than any other Father of the Church to develop the doctrine of Original sin, mostly in reaction to his disputes with Pelagius and Caelestius, which remain in Augustine's numerous writings.
It should be mentioned when assessing the alleged teachings and sayings of Caelestius and Pelagius that the works of neither exist today, although fragments of what is believed to be their writings remain quoted in the works of Augustine and Jerome.
Caelestius also joined with Pelagius in stating that the sin of Adam, as chronicled in the Biblical Book of Genesis had only harmed himself, and not all of humanity, as Augustine had taught in his writings and sermons. In several books on the topic, Augustine also argued that Pelagius and Caelestius neglected to take God's divine grace into account. Augustine believed Adam's sin ("Fall") in the Garden of Eden had caused human beings to lose the ability to not sin. ("non posse non peccare" in Latin) and therefore, all good deeds done by Christians come from them being enabled by God to do good.
In 411, the same year they arrived in North Africa, Caelestius faced a council in Carthage to defend his views. His accuser, the deacon Paulinus of Milan, listed six of Caelestius' ideas to be counted as heresies, but it is worth noting there is no recorded confirmation that Caelestius identified his views in the same way:
The fragmented transcripts of this council can be found under the section below entitled Related links and sources.
Later, it is recorded that Pelagius claimed in a synod that he did not agree with all of Caelestius' teachings. In Carthage, two local synods formed and condemned Pelagius and Caelestius without their presence. After being banished from Constantinople and condemned by Pope Innocent, Caelestius brought his case to Pope Zosimus. Zosimus was initially impressed by Caelestius' confessions of faith. However, after a new synodal letter of the African council of May 1, 418 to the pope, and after the steps taken by the emperor Honorius against the Pelagians, Zosimus was convinced both Caelestius and Pelagius were heretics. Zosimus issued his Tractoria, in which Pelagianism and its authors were finally condemned. No further information is known about Caelestius after this time.
The teachings of Pelagius and Caelestius were taken up by the Bishop Julian of Eclanum (ca. 386 - 454.)

