 In principle Augustine follows the view of the ancient eudaimonists that virtue is sufficient or at least relevant for happiness. There are however several important modifications. (1) The entire structure is made dependent on God’s prevenient grace. True virtue guarantees true happiness, but there is no true virtue that is not a gift of grace.  (2) Augustine accepts Cicero’s definition of virtue as the art of “living well” but emphatically rejects his equation of living well and living happily, i.e., the Stoicizing claim that a virtuous disposition is equivalent to happiness (De libero arbitrio 2.50; De civitate dei 4.21; De moribus 1.10; contrast Cicero, Tusculan Disputations 5.53). Our postlapsarian life on earth is inevitably the locus of sin and punishment, and even the saints are unable to overcome the permanent inner conflict between “the spirit” and “the flesh”, i.e., between good and evil volitions or rational and irrational desires in this life (De civitate dei 19.4, quoting Galatians 5:17). The perfect inner tranquility virtue strives for will only be achieved in the afterlife. (3) Augustine replaces the ancient definition of virtue as “right reason” (as in Stoicism) or “activity in accordance with reason” (as in the Aristotelian tradition) with a definition of virtue as love of God or, in later texts, as love of God and neighbor. Virtue is an inner disposition or motivational habit that enables us to perform every action we perform out of right love.  There are several catalogues of the traditional four cardinal virtues prudence, justice, courage and temperance that redefine these as varieties of the love of God either in this life or in the eschaton (De moribus 1.25; Letter 155.12; cf. Letter 155.16 for the cardinal virtues as varieties of love of the neighbor; De libero arbitrio 1.27 for descriptions of the virtues in terms of good will). His briefest definition of virtue is “ordered love” (De civitate dei 15.22). This does not mean that virtue becomes non-rational (for Augustine love and will are essential features of the rational mind; see  6.2 The Human Mind as an Image of God),  but it does mean that it becomes essentially intentional. The criterion of true virtue is that it is oriented toward God. Even if Augustine occasionally talks as if the four cardinal virtues could be added to the Pauline or theological virtues of love, faith and hope to make a sum of seven (Letter 171A.2), they are best taken as a subdivision of love, the only one of the Pauline virtues that persists in the eschaton (Soliloquia 1.14).