Augustine of Hippo, Latin: Aurelius Augustinus Hipponensis; (13 November 354 – 28 August 430), also known as Saint Augustine, Saint Austin, Blessed Augustine, and the Doctor of Grace (Latin: Doctor gratiae), was an early Christian theologian and philosopher whose writings influenced the development of Western Christianity and Western philosophy. He was the bishop of Hippo Regius (modern-day Annaba, Algeria), located in Numidia (Roman province of Africa). He 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 and Confessions. According to his contemporary, Jerome, Augustine “established anew the ancient Faith.” In his early years, he was heavily influenced by Manichaeism and afterward by the neo-Platonism of Plotinus. After his baptism and conversion to Catholicism in 387, 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 developed the concept of 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 City of God. In the Catholic Church, he is a saint, a preeminent Doctor of the Church, and the patron of the Augustinians. His memorial is celebrated on 28 August, the day of his death.