The Roman Empire of the fourth century AD, ruled by the Emperor Constantine the Great, was a society marked by social, religious, and political transformation as the empire came under the influence of the Christian Church. To understand how this period's emperors and bishops, among other political and social actors, thought about and enacted political theory, Nathan Israel Smolin turns to theological sources, revealing an age of profound political, social, and religious ferment, in which ideas and structures fundamental to the history of the following millennia were developed and contested--ideas that continue to shape our world today.