The English word Pagan is derived from the Latin ‘paganus’. This, in turn, was derived from ‘pagus’, meaning rural, country, provincial. It appears the word gained its religious sense with the rise of Christianity in the Empire. Christianity, initially a sect of Judaism, imported from the Levant, first took root in the cities among the merchants and slaves. Within the Empire, and later without, those in the countrysides held on longest to the native European religion. During this time, pagan was synonymous with both ‘gentile’ and Greek (hellene), as it was used by immigrant Jews and Christians to refer to the locals. In addition to the corruption that seems to be the natural residue of centralized governance, the Roman Empire became too large to manage with the available political technology. For this and other reasons, the nexus of cosmopolitanism began to collapse: just as the idea of a unified humanity, organized around a singular power, began to take root at the intersection of Judaism, Christianity, and Neoplatonism.
Groups of travelers, immigrants, sojourners, and the like who had previously rode the wave of Roman globalism increasingly found themselves rootless in somewhat unfamiliar places. The outsiders had already begun creating ethnic and religious communities within their gentile, Hellenic, pagan hosts, and practices and policies connected to Empire, such as external trade, assimilation, preoccupation with frontiers, and a more exploitative and less filial relation between the rulers and the ruled meant that these societies-within-societies were ignored, and thus allowed to grow. Drawing from an already-long history of living as a dispersed people, the Jews (and by extension the Christians), were accustomed to creating dispersed networks of cells that were largely invisible to the native people so that by the time. The Jews remained a separate society, connected to their god, who loved and cherished only this singular, chosen tribe. The Christians, on the other hand, whose formative origins coincided with Roman cosmopolitanism, developed an idea of a universal god. The Christians, then, were more open, evangelistic, and visible.
In 218, AD, a 14-year old Syrian priest of another foreign religion (Elagabalus) was crowned emperor. He forwarded a portrait of himself in sacredotal robes of silk and gold, covered in collars, bracelets, and gems of immeasurable value, and with eyebrows and cheeks painted in the feminine fashion. He married a vestal virgin and attempted to install his god as the primary deity of the Parthenon. Although empire brought great wealthy, surely there were those among the old and noble houses of Rome who felt things were moving in the wrong direction. In fact, by the time Decius became Emperor in 250, each preceding ruler had been assassinated/killed by the Roman army in one way or another. Many were concerned the social fabric responsible for the rise of Rome was being stretched, unraveled, and intentionally torn apart. This, at least in part, led Decius to restore the position of Censor, who would act independent of the Emperor, and to announce the edict that everyone (except the Jews) was required to pay official and public homage to the traditional Roman gods.
Soon thereafter, Decius and his son died in battle against the Germans. By the time Valerian tried to follow Decius’s example, the Senate and the Army were becoming Chrisitianized. And by the time Constantine declared himself a Christian, the power structure in the West was dominated by Christians, who now saw the Greek-speaking hellenic pagans, who gave birth to their culture, as somewhat foreign, and those of the native religion in the West as rural peasants or old-family aristocrats.
The World of Late Antiquity (1989), Peter Brown