Few figures in the history of Late Antiquity have attracted as much admiration, criticism, and scholarly scrutiny as Constantine. His reign stands at the intersection of two of the most consequential developments of the ancient world: the transformation of Roman imperial government and the emergence of Christianity as a public and institutionally privileged religion. For centuries, historians have debated whether Constantine's embrace of Christianity represented a sincere religious conversion, a calculated political strategy, or some complex combination of both. Yet an exclusive focus on the emperor's personal beliefs risks obscuring a larger historical process. The significance of Constantine lies not merely in what he believed, but in what his position as emperor enabled him to do. Through the resources of the Roman state, the authority of imperial office, and the mechanisms of patronage that permeated Roman society, he altered the social location of Christianity in ways that would shape the Mediterranean world for centuries.
This book proceeds from the premise that the Constantinian era is best understood not simply as a story of conversion or doctrinal change, but as a transformation in the relationship between religious communities, political authority, and public life. Prior to Constantine, Christianity existed within the empire as a minority movement. Though increasingly diverse, geographically widespread, and institutionally sophisticated, Christian communities generally functioned outside the structures of imperial power. Following Constantine's rise, Christianity became integrated into systems of governance, public representation, urban development, philanthropy, law, and social authority. This process was neither immediate nor uniform. It unfolded through negotiations among emperors, bishops, aristocrats, local communities, and competing religious traditions. Nevertheless, the result was the gradual emergence of what may be called public Christianity: a form of Christianity that was no longer confined to congregational settings but became visible, influential, and institutionally embedded within the public life of the Roman Empire.