Many historians believe that central to the rise of Christianity was the simple fact that Christians generously loved each other and their neighbours. They point out that in the ancient world mercy was widely seen as a character defect that ran counter to justice. Justice demanded people get what they deserved and was seen as appropriate, where mercy extended grace, love, and kindness to people who had done nothing to deserve it. Yet the Christians valued mercy. Christian communities became places where people tended to live longer and healthier lives, for when they suffered sickness, poverty or mishap they had brothers and sisters in Christ who provided for their need. And Christians extended love way beyond the boundaries of family and congregation to their pagan neighbours.
In 251 A.D. for example, a great plague struck the Greco-Roman world. Memories were revived of a plague a century earlier in which more than a third of the population died. Fear was everywhere. Those who could afford it fled to the countryside. Those who could not remained in the cities. When they went to the temples they found them empty, the priests having fled. The streets were filled with those who had become infected, their families left with no option but to push them out the door. Christian communities however took an entirely different approach. They saw it as their responsibility to love the sick and dying, so they took them into their homes and nursed them. This action meant that many people recovered who otherwise would have died. Historians suggest that elementary nursing could have reduced the mortality rate by as much as two thirds, but it also cost a number of Christian carers their lives.
In The Early Church, Henry Chadwick comments:
The practical application of charity was probably the most potent single cause of Christian success. The pagan comment ‘see how these Christians love one another’ (reported by Tertullian) was not irony. Christian charity expressed itself in care for the poor, for widows and orphans, in visits to brethren in prison or condemned to the living death of labour in the mines, and social action in time of calamity like famine, earthquake, pestilence, or war.
So striking was the Christian commitment to generous love that when the fourth century Emperor Julian sought to restore paganism to the Empire he instructed the pagan priesthood to follow the example of the Christians:
Why, then, do we think that this is enough, why do we not observe that it is their benevolence to strangers, their care for the graves of the dead and the pretended holiness of their lives that have done most to increase atheism ? I believe that we ought really and truly to practise every one of these virtues… For it is disgraceful that, when no Jew ever has to beg, and the impious Galilaeans support not only their own poor but ours as well, all men see that our people lack aid from us.
Source: Historical data derived from Henry Chadwick, The Pelican History of The Early Church and Rodney Stark, the Triumph of Christianity