The Seriousness of the Pelagian Error

The reason that Pelagianism is such a serious theological error is that the glory of the gospel (and thus of God Himself) is necessarily dimmed. This happens in two way: 1) by representing the bad news of Adam's fall as less bad and 2) by representing the good news of God's grace as less good.

First, it represents the bad news of Adam's fall as less bad. The brightness of an object is made more apparent by its background. The glory of the gospel is most clearly seen against its real backdrop of human desperation and neediness. However, Pelagianism removes this backdrop in two ways: 1) it denies that humans have original sin. It teaches that only individual acts of the will can be described as sinful—not natures, dispositions, tendencies, or characters. As such, Adam did not acquire a sinful nature in any sense of the word as the result of his sin, and, thus, it was impossible for Adam to propagate a sinful nature to his descendants, much less any guilt for that sin. 2) It denies that humans suffer from radical corruption. It teaches that all humans are morally neutral, having no tendency to commit sin. In fact humans have an absolutely free and independent will, completely able to decide between good and evil and and execute those decisions with no limitation. As is pretty clearly seen from these two points, Pelagianism casts the human estate in a pretty positive light, completely contrary to the orthodox position that “The sin of the first man has so impaired and weakened free will that no one thereafter can either love God as he ought or believe in God or do good for God's sake, unless the grace of divine mercy has preceded him” (Canons of the 2nd Council of Orange). And as such, Pelagianism diminishes man's neediness and thus diminishes the glory of the gospel.

Secondly, it represents the grace of God as less good. Grace is reduced to external operations. For example, it was God's grace to give His law and to give Christ as examples of righteousness in order to make it easier to abstain from sin. But this is a very minimalist notion of grace. It makes grace helpful but not strictly necessary. The fact is that salvation is by grace from beginning to end. Election unto salvation, effectual calling, and perseverance in faith are all the result of God's free and unconstrained grace. God's grace is both the necessary and sufficient cause of salvation; it is not merely helpful. So it is clear that Pelagianism detracts from the glory of the gospel by also devaluing the grace of God.

In summary, Pelagianism dims the glory of the gospel both by pretending that man's estate is better than it really is and by pretending that God's gracious involvement in our salvation is helpful but not necessary. Therefore, for this reason, it is a serious theological error.