Pelagius was a theologian who advocated free will and asceticism. He was accused by Augustine of Hippo and others of denying the need for divine aid in performing good works. They understood him to have said that the only grace necessary was the declaration of the law; humans were not wounded by Adam's sin and were perfectly able to fulfill the law without divine aid. Pelagius denied Augustine's theory of original sin. His adherents cited Deuteronomy 24:16 in support of their position. Pelagius was declared a heretic by the Council of Carthage . His interpretation of a doctrine of free will became known as Pelagianism.
He was well educated, fluent in both Greek and Latin, and learned in theology. He spent time as an ascetic, focusing on practical asceticism. He was well known in Rome, both for the harsh asceticism of his public life and the power and persuasiveness of his speech. His reputation earned him praise early in his career even from such pillars of the Church as Augustine, who referred to him as a "saintly man". However, he was later accused of lying about his own teachings to avoid public condemnation. Most of his later life was spent defending his doctrine against Christian theologians who held that Pelagius was spreading novelties in the Faith unknown to the apostolic tradition.
Due to some calling him a heretic, little of his work has come down to the present day except in the quotes of his opponents. However, more recently, some non-Orthodox Christian authors have defended Pelagius as a misunderstood “orthodox”:
Recent analysis of his thinking suggests that it was, in fact, highly orthodox, following in the tradition established by the early fathers and in keeping with the teaching of the church in both the East and the West. ... From what we are able to piece together from the few sources available... it seems that the Celtic monk held to an orthodox view of the prevenience of God's grace, and did not assert that individuals could achieve salvation purely by their own efforts...
Wikipedia
Letter to Demetrias
On Virginity 6.1
[Harrison, Carol, Truth in a Heresy?, The Expository Times, 2016, 112, 3, 78–82, 10.1177/001452460011200302]
On Virginity
