Augustine is the last of ancient Christian writers, and the forerunner of medieval theology. Augustine influenced not only the current theology of his time, but also influenced the medieval theology and the sixteenth-century Protestant theology.
Augustine's theology was developed as a result of issues that faced him throughout his life. Therefore we need to look at his biography, because his life helped shaped his theology.
Augustine led a sinful life as a young child and a teenager. He was converted to Manichaeism in Tagaste. The rational explanation of the universe attracted him to Manichaeism (Conversion1).
Augustine's dissatisfaction with the answers offered by the followers of Mani led him to leave Manichaeism. He was then attracted to Neo-Platonism, because it offered the answers to two questions that eventually led him to intellectual acceptance of Christianity: the incorporeal nature of God and the existence of evil (Conversion2).
Augustine was intellectually converted to Christianity but could not change his lifestyle and become chaste. He was finally converted in the garden of Milan (Conversion3) (see picture above).