The condition of the church in the beginning of the fifth century gave the adversary an opportunity to bring in a new heresy, which introduced a fresh controversy that has continued with more or less violence from that day even until now. This was Pelagianism. The great heresy, Arianism, which had hitherto agitated the church, originated in the East and related to the Godhead of Christ; one was now to arise in the West, which had for its subject the nature of man after the fall and his relations to God. The last misrepresented the lost sinner; the first, the divine Savior.
Pelagius is said to have been a monk of the great monastery of Bangor, in Wales; and probably the first Briton who distinguished himself as a theologian. His real name was Morgan. His follower, Celestius, is supposed to have been a native of Ireland. Augustine speaks of him as younger than Pelagius—bolder and less crafty. These two companions in error visited Rome, where they became intimate with many persons of ascetic and saintly reputation, and disseminated their opinions with caution and in privacy; but after the siege in the year 410 they passed into Africa, where they more openly advanced their opinions.
It does not appear that Pelagius was animated by any desire to form a new doctrinal system, but rather to oppose what he considered moral indolence, and a worldly spirit among his brethren. Hence he maintained that man possessed inherent power for doing the will of God, and for reaching the highest degree of holiness. In this way his theological views were to a great extent formed and determined. But utterly false as they are, they were only consistent with his rigid asceticism, and its native fruit. As scripture undeniably refers all good in man to the grace of God, Pelagius too, in a sense of his own, acknowledges this; but his ideas of divine grace were really nothing more than outward means to call forth man's efforts: a work of heavenly grace in the heart, and the operations of the Holy Spirit he did not think were needed. This led him to teach that the sin of our first parents had injured no one but themselves; that man is now born as innocent as Adam was when God created him, and possessed of the same moral power and purity. These doctrines, and such as are connected with them, especially the idea of man's free will—"an unbiassed power of choosing between good and evil," Pelagius and his colleague, Celestius, secretly disseminated in Rome, Sicily, Africa, and Palestine; but, excepting in the East, the novel opinions were generally condemned. There, John, bishop of Jerusalem, who considered the doctrines of Pelagius as agreeing with the opinions of Origen, to which John was attached, patronized Pelagius, allowing him to profess his sentiments freely, and to gather disciples.