Saint Augustine of Hippo (November 13, 354 August 28, 430), was a Berber philosopher and theologian. Augustine, a Latin church father, is one of the most important figures in the development of Western Christianity. Augustine was heavily influenced by the Neo-Platonism of Plotinus. He framed the concepts of original sin and just war. When the Roman Empire in the West was starting to disintegrate, Augustine developed the concept of the Church as a spiritual City of God (in a book of the same name) distinct from the material City of Man. His thought profoundly influenced the medieval worldview. Augustine's City of God was closely identified with the church, and was the community which worshipped God. Augustine was born in the city of Thagaste, the present day Souk Ahras, Algeria, to a Catholic mother named Monica. He was educated in North Africa and resisted his mother's pleas to become Christian. Living as a pagan intellectual, he took a concubine and became a Manichean. Later he converted to the Catholic Church, became a bishop, and opposed heresies, such as the belief that people can have the ability to choose to be good to such a degree as to merit salvation without divine aid (Pelagianism). In Roman Catholic Church and the Anglican Communion, he is a saint and pre-eminent Doctor of the Church, and the patron of the Augustinian religious order; his memorial is celebrated 28 August. Many Protestants, especially Calvinists, consider him to be one of the theological fathers of Reformation teaching on salvation and divine grace. In the Eastern Orthodox Church he is blessed, and his feast day is celebrated on 15 June, though a minority are of the opinion that he is a heretic, primarily because of his statements concerning what became known as the filioque clause. Among the Orthodox he is called Blessed Augustine, or St. Augustine the Blessed.