This book is, along with Inner Grace (OUP 2008), a sequel to Phillip Cary's Augustine and the Invention of the Inner Self (OUP 2000). In this work, Cary argues that Augustine invented the expressionist type of semiotics widely taken for granted in modernity, where words are outward signs giving inadequate expression to what lies within the soul. Augustine uses this new semiotics to explain why the authority of external teaching, including Biblical authority, is useful but temporary, designed to lead to a more permanent Platonist vision granted by the inner teacher, Christ, who is the eternal Wisdom of God. In fact, for Augustine we literally learn nothing from words or other outward signs, which are useful only as admonitions or reminders pointing out the right direction for us to look in order to see for ourselves, with the inner eye of our own mind. Even our knowledge of other people is ultimately a matter of seeing what is in their souls, not putting faith in their words. Cary argues that for Augustine outward signs cannot give us knowledge because all bodily things are fundamentally powerless, incapable of conveying an inner good to the soul. This also leaves no room for a concept of efficacious external means of grace ? not even the flesh of Christ. The sacraments, which Augustine was the first to describe as outward signs of inner grace, signify what is necessary for salvation but do not confer it. Baptism, for example, is necessary for salvation, but its power is found not in water or word but in the inner unity, charity, and peace of the church. Along with its companion work, Inner Grace, this careful and insightful book breaks new ground in the study of Augustine's theology of grace and sacraments.