A celebrated heresiarch of the 5th century, born in Britain or Brittany; denied original sin and the orthodox doctrine of divine grace as the originating and sustaining power in redemption, a heresy for which he suffered banishment from Rome in 418 at the hands of the Church. A modification of this theory went under the name of Semi-Pelagianism, which ascribes only the first step in conversion to free-will, and the subsequent sanctification of the soul to God's grace.