This paper examines the relationship between Constantine I, the first Roman emperor to convert to Christianity, and Eusebius of Caesarea, his foremost biographer and ecclesiastical historian. Drawing on sources including Gonzalez, Pohlsander, and Grafton and Williams, the paper traces how these two men — a powerful emperor seeking religious unity and a prolific scholar-bishop — collaborated, however distantly, to transform Christianity from a persecuted minority religion into the dominant civic faith of the Roman Empire. The paper considers their personal interactions, mutual recognition of shared goals, the Arian controversy, and the lasting legacy of Eusebius's theological and historical writings, particularly the Vita Constantini, in shaping Constantine's enduring reputation.
There are many great rulers in history — men and women of great fortitude, power, allegiance, wealth, and intrigue. Yet few ring more interesting to a modern reader than Constantine I, widely held as the first Roman emperor to convert to Christianity and to spread its favor across the then-known world. This paper briefly discusses Constantine I (27 February 272 – 22 May 337 AD) and his foremost surviving biographer, Eusebius (263–339 AD), who was in many ways writing the history of the church rather than the biography of a single human leader. The paper first explores who these men were according to history, then examines their relationship to one another, the impact that relationship had on each, and finally how that relationship influenced the enculturation of Christianity in the Roman Empire.
Constantine the Great (Flavius Valerius Aurelius Constantius Augustus) — also known as Constantine I and sometimes as Saint Constantine — served as Roman emperor from 306 to 337 AD, the 57th emperor of the Roman Empire. He was a consummate military ruler who reinvigorated the empire, rebuilding through military might its size and strength. He is best known for being the first Roman emperor to personally convert to Christianity, a distinction that owes much to the limited sources surviving from his reign.
Much of what is known about Constantine comes from the writings of a single Christian author: Eusebius, the bishop of Caesarea in Palestine, who recorded Constantine's life through the lens of Christian conversion and thereby left a foundational legacy that firmly seats Christianity in the Roman Empire at the moment it begins to win favor as a dominant religion. In many ways, the controversies of Constantine's reign — which was militarily bloody and historically comparable to those of other rulers — are refracted through Eusebius's repeated claims of Constantine's greatness viewed through the window of Christianity, rather than through his military might and dominating statecraft.1
There is limited evidence of a personal relationship between Eusebius and Constantine. What evidence exists begins mainly with a brief meeting of the two in Palestine, prior to Constantine's assumption of the role of emperor, and likely culminates with Constantine's trip to Jerusalem for the dedication of the newly built Church of the Holy Sepulchre. Eusebius was the bishop of the principal city in that region and therefore played an important role in the celebrations, likely having several audiences with Constantine — a connection supported in part by years of distant correspondence and a few other personal meetings.
Eusebius recognized in Constantine a leader willing and desirous of bringing peace to the church, while Constantine recognized in Eusebius an admired and therefore influential individual and actively supported him. According to Gonzalez, a foremost scholar on the early church, their relationship was neither that of close friend nor courtier, as each occupied distant and important roles. Nevertheless, each seemed to recognize the role of the other and to cultivate mutual respect on that basis.2 This is not to say that the men were mere opportunists, but rather that each recognized shared goals and utilized the relationship — brief and intermittent as it was — to pursue them. In Eusebius's view, the mutual goal was to strengthen and unify the Christian Church during and after a serious rift: the Arian controversy. Eusebius wavered on the theological substance of that dispute, but his primary concern was unity rather than disunity — a position openly favored by Constantine throughout his years as emperor.3
Also according to Gonzalez, while Constantine was alive Eusebius found occasion to praise him in dedications but did not do so fully until after Constantine's death, in the form of the work that has become one of only two official biographical sources for Constantine's rule. Though fully embedded in church history and canon, the Vita Constantini is as much a history of Constantine as it is a faith-filled retelling of the role he played in church unity. The only other surviving biographical work is the anonymous Origo Constantini Imperatoris, which details his military and civil history rather than his role in the church.4 For most scholars of Constantine, the two works together form a relatively comprehensive biography of the man and his place in the empire.
The reality of the relationship between these two men — relatively scarce on a personal level — has more to do with what they accomplished together for the still-fledgling Christian church: decisive unity after the Arian controversy, and the enduring legacy of Eusebius's theological praise of Constantine, not so much as a man but as a unifier and spreader of Christianity. It is largely because of Eusebius as a consummate writer and theological historian that Constantine's legacy is so heavily focused on his role in the Christian church. Regardless of the controversy surrounding his conversion in 312, he is and will forever be known as the first Christian emperor as well as the first to advocate for religious tolerance — whatever the full scope and scale of that truth may be in comparison to his ruthless military record.5
With regard to the roles of Constantine and Eusebius as architects of Christian unity and acculturation, significant evidence remains. This evidence begins with the role Eusebius played in recording the history of the church, drawing on a historically vast library of sources ranging from Jewish texts to military histories. He was both a scholar and a diligent historian, working at what must have been a feverish pace to bring his knowledge to his audience while managing the daily and no doubt demanding responsibilities of a bishop in a prominent Roman city.
It is often said that behind each great man stands a great historian as the dominating force shaping his legacy, and the relationship between Constantine and Eusebius is a grand historical example of just such a pairing. Each saw within the other a complementary role and cultivated it in order to develop a legacy that neither might have expected. Eusebius, both before and after Constantine's death, fully understood the role Constantine might play in the growth and strength of a unified church — one that had been fractured by major controversies and defined throughout its history by personal and civic persecution. The period of Constantine's rule marked the first time in history when to be a Christian was to be an accepted, even ordinary, part of civic life in the Roman Empire.
"How Eusebius surpassed Origen in scope and method"
"Combined impact of both men on Roman Christian culture"
Constantine clearly developed a standard for the acculturation of Christianity, as his desire to unify the church and remove it from persecution is well known. Yet this prestigious ideal would not ever have been known in Constantine's time, or later as his legacy, had it not been for Eusebius — a scholar with a singular aim: to unify and acculturate the Christian Church within the Roman Empire. The enduring adage that history is written by its authors is powerfully exemplified in this period, when Eusebius utilized the legacy and dominance of Constantine — a clearly like-minded individual — to champion the victory of Christian ideas and to create scholarly and social dominance across the various cultures of the empire.
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