This biography of Church Father Athanasius the Great emphasizes Athanasius' role as a passionate opponent of Arianism and advocate of the ideas established at Nicaea of the essential unity of God the Father and the Son. Approaching his subject from both a historical and a theological perspective, the author shows the centrality of this debate to the formation of Christianity and the Western Roman Empire. He presents a portrait of "Athanasius contra mundum" (Athanasius against the world): after becoming archbishop of Alexandria, Athanasius was sent into exile five times, and called back each time by the emperor.