Rodney Stark:”(The Rise of Christianity: How the Obscure, Marginal Jesus Movement Became the Dominant Religious Force in the Western World in a Few Centuries [HarperCollins Publishers, 1997, Chapter 4].)”: argues persuasively at one point in his book that the rise to dominance of Christianity in the Roman Empire was greatly facilitated by the epidemics (probably smallpox and measles) which hit the Empire in 165 and 251 and killed between 1/4 and 1/3 of the population.
One major reason for this was the greater explanatory power of Christianity over that of the pagan religions. While the just and the unjust unlike died, the pagan religions, in the persons of their priests, fled the scene, concerned only for self-preservation. The philosophers, too, sat around musing abstractly about the decline of Virtue in an elderly world. People shunned sick relatives and friends, leaving them to die alone and unmourned. The famous ancient physician Galen, so celebrated by historians of science, himself fled the cities so as to avoid contracting the plague himself–ironically leaving him with little ability to write scientifically about it. Meanwhile, the Christians invested themselves in caring for the sick and dying–even at the cost of themselves getting sick and dying. As well, Christianity provided, via the doctrine of the resurrection of the dead and the hope of living with Christ forever, a far better foundation for seeing life as meaningful even amidst the horror of the epidemics.
To the Christians, the plagues were merely “schooling and testing” for the better things in life. Bishops wrote stirring letters to their parishioners, exhorting them to good works. Cyprian of Carthage noted of “these trying exercises” that “by contempt of death they prepare us for the crown.” Dionysius of Alexandria spoke of this “time of unimaginable joy” when “Most of our brother Christians showed unbounded love and loyalty, never sparing themselves and thinking only of one another.” In his biography of Cyprian, Pontianus reported that the saint reminded his people that the Gospel requires Christians to have a righteousness that exceeds that of the heathens and publicans. Hence, “the good was done to all men, not merely to the household of faith.” While the pagans reacted in sheer terror or prattling acceptance, the Christians lived a life amdist death that powerfully illustrated the superiority of their Faith. So great was their witness that even a hundred years later the last great pagan Emperor, Julian the Apostate, felt compelled to urge his fellow pagans to strive to outdo “the Galileans,” for “[they] support not only their own poor, but ours as well, everyone can see that our people lack aid from us.”
Christian nursing of the sick, in turn, greatly aided survival rates during the plagues. The pagans saw a difference in the religions, and many of them wanted what the Christian Faith had to offer. Stark uses basic algorithms of social science to demonstrate, using plausible estimates, that even aside from conversions Christianity would have grown in influence through the plague periods merely because the end result of the Christian nursing of the sick would have been an increase in the ratio of Christians to pagans. Also, because the Christians cared for each other, their birth rates would not have declined as did those of the pagans. Still further, the higher Christian survival rate would have created many Christians who were immune to subsequent infection, allowing them to pass unscathed through masses of infected pagans. This would have seemed frankly miraculous to the pagans, as if it the basic Christian charity and courage in the face of death were not already miraculous enough! And since in the ancient world, the miraculous was a key component in the plausibility of religious claims, it stands to reason that the Christian claims would appear increasingly plausible.
Such a testimony, Stark argues, is a significant reason why Christianity triumphed in the ancient world. Its culture was simply superior to that of the pagans.