c. 354–418) was a British (Brittonic) theologian known for promoting a system of doctrines (termed Pelagianism by his opponents) which emphasized human choice in salvation and denied original sin.

[1] Pelagius was accused of heresy at the synod of Jerusalem in 415 and his doctrines were harshly criticized by Augustine of Hippo, especially the Pelagian views about mankind's good nature and individual responsibility for choosing asceticism.

[1] He was said by his contemporaries, such as Augustine of Hippo, Prosper of Aquitaine, Marius Mercator, and Paul Orosius, to have been of Celtic British origin.

Pelagius was also highly educated, spoke and wrote Latin and Greek with great fluency, and was well versed in theology.

His name has traditionally been understood as a Graecized form (from pélagos, "sea") of the Welsh name Morgan ("sea-born"), or another Celtic equivalent.

When in 414 disquieting rumours arrived from Sicily and the so-called Definitiones Caelestii, said to be the work of Caelestius, were sent to him, he at once (414 or 415) published the rejoinder, De perfectione justitiae hominis.

Church sources claim Orosius' lack of fluency in Greek rendered him unconvincing and John's Eastern background made him more willing to accept that humans did not have inherent sinfulness, yet the council rendered no verdict and passed the controversy to the Latin Church because Pelagius, Jerome, and Orosius were all Latin.

He showed letters of recommendation by other authoritative figures, including Augustine himself — who, for all their disagreements, thought highly of Pelagius's character.

[citation needed] The Synod of Diospolis therefore concluded: "Now since we have received satisfaction in respect of the charges brought against the monk Pelagius in his presence, and since he gives his assent to sound doctrines but condemns and anathematises those contrary to the faith of the Church, we adjudge him to belong to the communion of the Catholic Church.

[15] The view that mankind can avoid sinning, and that humans can freely choose to obey God's commandments, is held to have stood at the core of Pelagian teaching.

[20] Seeking to undo his condemnation, Pelagius wrote a letter and statement of belief to Pope Zosimus, Innocent I's successor, arguing that he was orthodox.

Because little information remains with regard to Pelagius' actual teachings, some of his doctrines possibly were subject to revision and suppression by his enemies (followers of Augustine and the Church leadership as a whole at that time).

Evaluation of him changed after the publication of a 1943 biography by Georges de Plinval and more recent scholars have viewed him as an orthodox Christian theologian who was a victim of denunciation.

[25] According to the scholar Rebecca Weaver, "what most distinguished Pelagius was his conviction of an unrestricted freedom of choice, given by God and immune to alteration by sin or circumstance.

His fault was in exaggerated emphasis, but in the final form his philosophy took, after necessary and proper modifications as a result of criticism, it is not certain that any statement of his is totally irreconcilable with the Christian faith or indefensible in terms of the New Testament.