On the contrary, this essential nature is distorted by what Augustine calls, in the tradition of the New Testament and the Church, sin, and especially original sin. His doctrine of sin, the center of his anthropology, his doctrine of man, was developed in his fight with Pelagicus.
We must now turn to this struggle, which is one of the great struggles in Church history, like the Trinitarian and Christological struggles, which we have discussed, and it: is one which repeats itself again and again. We have the tension already in the New Testament between Paul and the writers of the Catholic Letters; we have it in Augustine and Pelagicus; we have it somehow between Thomas and the Franciscans; we have it between Karl Barth and the present-day liberals. It is something which goes through the whole history of the Church. And there is always one point which is decisive. Usually it is discussed in terms of the concept of freedom, but this is misleading because freedom has so many connotations which are not relevant for this discussion. But it is the question of the relationship of religion and ethics, whether the moral imperative is dependent on the Divine grace in its actualization, or whether Divine grace is dependent on the fulfillment of the moral imperative. That is actually the question which is going on through all Church history. In abstract terms, you could say it is the relationship of religion and ethics.
Pelagicus is not a special heretic. He represents simply the ordinary doctrine of people who were educated in Greek thinking, especially in Stoic traditions, and for whom freedom is the essential nature of man. Man is a rational being, and a rational being includes freedom of deliberating, deciding. All this wouldn’t have made him a heretic because most of the Eastern church had exactly the same idea of freedom. But he developed them in a way which brought him into conf lict with Augustine. When this conf lict was decided, Augustine was at least partly victorious and Pelagicus was an arch-heretic, whose name was used all the time as a name of one of the classical Christian heresies.