Saint Augustine of Hippo was a Roman African, early Christian theologian and philosopher from Numidia whose writings influenced the development of Western Christianity and Western philosophy. He was the bishop of Hippo Regius in north Africa and is viewed as one of the most important Church Fathers in Western Christianity for his writings in the Patristic Era. Among his most important works are The City of God, On Christian Doctrine and Confessions. According to his contemporary Jerome, Augustine "established anew the ancient Faith." In his youth he was drawn to Manichaeism, later to neo-Platonism. After his baptism and conversion to Christianity in 386, Augustine developed his own approach to philosophy and theology, accommodating a variety of methods and perspectives. Believing that the grace of Christ was indispensable to human freedom, he helped formulate the doctrine of original sin and made seminal contributions to the development of just war theory. When the Western Roman Empire began to disintegrate, Augustine imagined the Church as a spiritual City of God, distinct from the material Earthly City. His thoughts profoundly influenced the medieval worldview. The segment of the Church that adhered to the concept of the Trinity as defined by the Council of Nicaea and the Council of Constantinople closely identified with Augustine's On the Trinity.
