Pelagius in Wikipedia

Pelagius (ca. AD 354 – ca. AD 420/440) was an ascetic who denied the doctrine of original sin as developed by Augustine of Hippo, and 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, which his teachings clearly reflect. He was certainly well known in Rome, both for the harsh asceticism of his public life as well as the power and persuasiveness of his speech. His reputation in Rome 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 in order to avoid public condemnation. Most of his later life was spent defending his doctrine against theologians teaching the Catholic Faith. They held that Catholicism came from the apostles and that Pelagius was spreading novelties in the Faith unknown to the apostolic tradition. Due to his status as a heretic, little of his work has come down to the present day except in the quotes of his opponents. However, more recently some have defended Pelagius as a misunderstood orthodox...

Link: https://en.wikipedia.org/wiki/Pelagius