Recently I have been reading through Listening to the Beliefs of the Emerging Churches. Doug Pagitt has a very curious explanation for the tension between Augustine and Pelagius. In his estimation Pelagius' Celtic spirituality, the product of a Druidic northern culture, was always going to clash with Augustine's Greco-Roman view of God. Now aside of the fact that their respective theologies are explained solely in cultural terms (and I think quite inaccurately by Pagitt) and not in terms of their differing exegesis Scripture, Pagitt has got the wrong culture in mind. Jerome said at the time that Pelagianism was the heresy of "Pythagoras and Zeno." Dean Milman, noted that "the greater part" of Pelagius' letter to Demetrius "might have been written by an ancient academic." Pelagianism seems to him to be "a rehabilitation of the general heathen view of the world."
And it ought to be pointed out that explaining orthodoxy and heresy in such a way that culture accounts for both is itself the product of an unorthodox presupposition.
Here is Bavinck on Pelagius:
"According to Pelagius, the image of God consisted solely in free personality, not in positive holiness, immortality, and so on. Adam's trespass, according to him, did not deprive humans of the image of God and in fact had no adverse consequences whatsoever. There is no such thing as original sin. Adam's trespass negatively affected his descendants only in that it left them a bad example, which, followed by others, made sin a power among humankind...Sin, accordingly, is propagated not by generation but by imitation. Humans, whose souls were created pure by God, are still today born in the same state as Adam was before the fall...Human beings are still completely free and can of themselves know and do the good: they have no need of grace. It is indeed possible for them to abstain from all sins, and a few have in fact attained this ideal.
In voicing these ideas, Pelagius did little more than take over the views that had been promulgated long before by Greek and Roman philosophers and had found acceptance in popular philosophy."
Herman Bavinck, Reformed Dogmatics vol. 3: Sin and Salvation in Christ, (Baker: 2006), p. 86