Paul Freedman traces Christianity's rise to dominance in the Roman Empire following Constantine's conversion, and the brief pagan revival attempted by Julian the Apostate, Constantine's nephew. The lecture, part of Yale's Early Middle Ages course, examines the doctrinal splits that divided the fourth century church, particularly Arianism and Donatism, along with Manicheanism, and how emperors intervened through church councils to settle these disputes. Freedman closes by introducing St. Augustine's Confessions and the Platonist philosophy that shaped Augustine's thought. Chapter markers move from Julian's reign through the heresies and imperial responses to the turn toward Augustine, giving a clear sense of how religious controversy and imperial politics intertwined in late antiquity. Delivered as a standard classroom lecture with chapter timestamps, it is part of Yale's full Early Middle Ages, 284-1000 series available through Yale Online.