Pelagius is the first known British author, important because of his persuasive advocacy of two ideas: that human nature was inclined to goodness, and that man had free will. After a campaign to vilify him, he was excommunicated in AD 418 for allegedly inventing a new heresy, and his name was made synonymous with arrogance. This book shows that Pelagius defended the contemporary ascetic account of Christianity and that, far from being the leader of a separatist group, he was one of many propagandists for the ascetic movement which swept through Christianity at this time and generated medieval monasticism. Textual analysis proves that Pelagius did not teach the ideas attributed to him or propose anything new. It is impossible to differentiate between Pelagius’ writings and other ascetic literature, and there was no separate group of ‘Pelagians’. This book also examines how and why the myth was created, setting this process in its historical context and in the context of scholarship on the function of heresy in religion and sociological analysis of the creation of deviance. Finally, manuscript evidence supports the argument that ‘Pelagianism’ was a deliberately created myth. Travelling under false attributions, Pelagius’ writings were staples of monastic book collections because they contained the same ideas as other texts promoting the ascetic version of Christianity. In the fourteenth century, when Christians once more sought a confident anthropology, it was Pelagius’ works to which they turned. This book presents a paradigm shift in our understanding of the history of Christianity in the West.