The politically embroiled and sharply divided Council of Nicaea (325) provided a turbulent beginning to Christianity's struggle for self-definition in the political arena. Questions of ultimate truth aside, those who could legally claim the title of Christian orthodoxy were those whose teachings had the backing of the emperor's legal and military authority. Despite the concrete decisions of 325 and the ecumenical council's attempt to create an imperial orthodoxy, the decades that followed witnessed ongoing battles between those Christians who supported the council's outcome and those who did not.This book investigates the complex anti-Jewish and anti-Judaizing rhetoric of Ephrem, a fourth-century poet, deacon, and theologian from eastern Roman Syria whose Syriac-language writings remain unfamiliar and linguistically inaccessible to centuries of scholars who study the well-known Greek and Latin writings of his contemporaries. A critical reading of Ephrem's numerous poetic writings demonstrates that his sharp anti-Jewish and anti-Judaizing language helped to solidify a pro-Nicene definition of Christian orthodoxy, cutting off from that community in the very act of defining it his so-called Judaizing and Arian Christian opponents, both of whom he accused of being more like Jews than Christians.Through carefully crafted rhetoric, Ephrem constructed for his audience new social and theological parameters that reshaped the religious landscape of his community. This book shows that the anti-Jewish polemic of Ephrem's hymns represents his calculated efforts to leave his Syrian congregation with no viable alternative but to conform to the Council of Nicaea, his own model for Christian orthodoxy.Comparing Ephrem's texts with the contemporary Greek writings of Athanasius, the renowned bishop of Alexandria, Christine Shepardson reveals the significant role that anti-Jewish rhetoric played more broadly in this critical fourth-century theological conflict, and demonstrates that long-ignored Syriac-speaking Christians such as Ephrem participated fully in the fierce struggle to define Christian orthodoxy for the Roman Empire.