The spread of Christianity depended upon the social and political fabric of the Roman Empire. For two centuries after Christ’s death, a policy of passive persecution enabled the new cult to expand via the inter-urban networks of the ancient Mediterranean. Literate adherents adapted the philosophical and religious currents of the Hellenistic period and the Augustan Principate to their faith, drawing in upper-class Romans who had prided themselves on their allegiance to tradition. Finally, the official adoption of Christianity and Constantine’s intervention in church affairs clarified the early Church’s doctrinal orthodoxy and eradicated internecine disputes.
With a few notable exceptions, Roman emperors between Augustus and Trajan Decius were loath to actively persecute Christians, allowing for the spread of the religion amongst lower-class residents of the Empire. The exchange of letters between Pliny and Trajan (10.96-97) provides an apt summary of the Antonines’ disposition towards Christianity. Asking for guidance regarding the prosecution of alleged Christians, Pliny is told by his emperor that they “are not to be sought out,” and that they are to be forgiven upon apostatizing. There were lapses in this policy. Prejudice towards Christians existed, most of it based upon false assumptions about the cannibalistic and incestuous nature of the Holy Eucharist. Nero capitalized upon the perceived “misanthropy” of the early Christians by blaming them for the Great Fire of 64 A.D. Under Marcus Aurelius Christians residing in the Gallic city of Lugdunum were forced to fight as gladiators. Decius (249-251 A.D.), thinking that the anarchy of the third century resulted from the gods’ displeasure with the spread of Christianity, mandated that all citizens perform sacrifices to the traditional Roman pantheon. Diocletian’s Great Persecution (303-311 A.D.) would precipitate an administrative crisis that his Christian successor had to neutralize (see below). Nonetheless, Hadrian’s acquiescence in Trajan’s stated policy was the norm rather than the exception. Paul used his Roman citizenship to travel throughout Syria, Asia Minor, and mainland Greece, preaching the message of a resurrected Jesus as he went. The hostility of Law-abiding Jews and the recalcitrance of upper-class Romans ensured that early Christianity would confine itself overwhelmingly to lower-class Greek-speakers. Nonetheless, the “unofficial” channels of communication that existed under the Roman Empire-literate city dwellers and urban hierarchies that contributed to the organization of ekklesiai-ensured the religion would establish roots by the time the “Third Century Crisis” rolled around. As Mackay and Becker have noted, adherents of early Christianity were not limited to fanatic martyrs willing to perish for their beliefs; many were intimately connected to the social and economic life of their communities.
Christian authors also adapted their message to their cultural milieu. In addition to receiving a Rabbinic education, Paul had studied Neoplatonism, which had in the Timaeus expounded the doctrine of a divine “mind” that gave order to existence. (n.b. I here rely upon Richard A. Norris’ chapter on “The General Situation” preceding the rise of Christianity, found in the Fourth Edition of Williston Walker’s A History of the Christian Church). Justin Martyr, who is credited with establishing the genre of Christian apologetic, styled his epistles on the dialogues of Plato, arguing that Christians-like Socrates-were beneficial rather than harmful to society. The multiplicity of mono- and henotheistic cults that existed in the Roman Empire also meshed well with the fundamental tenets of Christianity. The worship of Mithras was widespread amongst the imperial soldiery. Manichaeanism, a dualistic offshoot of Zoroastrianism that began in 240 A.D., informed the thought of no less an Early Church Father than Augustine. Indeed, even after Constantine’s conversion to Christianity following his defeat of Maxentius at the Battle of the Mulvian Bridge (312 A.D.), appeals to Sol Invictus, the Unconquered Sun, continued to appear on his coinage until the early 320s. This theological cross-pollination eased the transition from paganism to Christianity for many upper-class Romans.
These trends would culminate in the adoption of Christianity as the official religion of the Roman Empire and a subsequent codification of Christian doctrine. The Edict of Milan (313 A.D.) granted recognition to Christianity for the first time. Constantine, as a triumphant Christian ruler, was perceived as an agent of God’s will on Earth, and said so himself in a letter to the Persian king Shapur. Christian leaders appealed to him as such. Hard-line bishops had coalesced around the person of Donatus, an Alexandrian bishop who insisted that those priests who yielded to the Great Persecution ought to be defrocked. Summoning a council at Rome, Constantine rebuked the Donatists and maintained the authority of a bishop whose ordination by complicit priests had been called into question. He intervened in disputes of a Christological as well as an administrative nature. Arius, another troublesome bishop from the East, had asserted that God the Father had created Jesus the Son out of nothing-that there “was a time when he [i.e. Jesus] was not.” A council that consisted overwhelmingly of Eastern bishops was convened at Nicaea in 325 A.D., whereat an anti-Arian creed emphasizing the “co-essence” of God and Jesus was adopted. Though imperial fealty to this creed would waver throughout the mid 4th century-Constantine’s son Constantius was an avowed Arian who tried to replace the Nicene creed with his own “heterodoxical” version in 359 A.D.-Theodosius and Gratian put the Arian controversy to bed with an adapted creed that strengthened the “orthodox” position in 381 A.D. Ever since the rise of Gnosticism, notes Mackay, a major concern of Christian literature had been who was in and who was out. Under Constantine, the Roman emperor began adjudicating such decisions. (n.b. that the sack of Jerusalem during the First Jewish Revolt of 66-73 A.D. resulted in the eradication of “Christ-followers” who also adhered to the Abrahamic Law; in this sense the Empire already had played a role in determining Christian orthodoxy).
The martyrs’ zealotry for the eternal hereafter notwithstanding, Christianity achieved prominence because rather than in spite of the Roman Empire.