The thought of Augustine on the two ethical categories of sin and grace is of great importance in the history of Christian theology. His system of grace and predestination prevailed for many centuries, although not without strong opposition, and underwent, through scholastic elaboration, substantial changes in order to save the freedom of the will; and finally it reappeared in the conception of the spiritual life shaped by Luther and the other teachers of the Reformation. It is on account of his doctrine about grace and predestination that Protestant theologians like to call Augustine “der Paulus nach Paulus und der Luther vor Luther.” Whatever may be the exactness of this genealogy, it shows at least the value and efficacy of the Augustinian conception of the natural and supernatural life on the development of the European spirit. In the Catholic tradition this thought of Augustine is at the very basis of the ethical, ecclesiological, and sacramental systems; in the Christian but non-Catholic movements this doctrine, interpreted in a rather paradoxical way, gave a starting-point to the Reformation.