Henri de Lubac's doctrine of grace and nature emerged out of the pastoral and sacramental context of confession. Although recent critics have assumed a Thomist setting, a close reading shows that the doctrine is rooted in de Lubac's critical engagement with Augustinianism. In the form of Jansenism and drawing especially on Augustine's late, anti-Pelagian writings, this sensibility pervaded modern French theology. Notwithstanding its distorted conceptions of grace's mode of operation and of human nature, Jansenism provoked de Lubac into developing new understandings of the relation between belief and knowledge, and of theological anthropology. In advocating for the continuity of Augustine's theology, de Lubac made an important contribution to Augustine scholarship. His resulting doctrine of grace and nature, in which the person of Adam is central, has wider, abiding theological salience.