There are three main related factors that contributed to the growth and expansion of Christianity, and ultimately its success. These were a combination of political, social and economic factors. The rise of early Christianity has been the topic of much debate and historical analyses. I will be attempting to simply outline and comment on some of the main social factors that lead to the rise of Christianity.
Christianity seems to have come at the right time, in an age where life was uncertain and many circumstances could not be controlled such as the barbarians invading; fires burning down whole cities and plagues killing off quite a lot of the population, whether you were rich or poor it made no difference, life in the Greco-Roman world was very fragile and short. Life expectancy was not great and the average person lived until around the age of 30 or even considerably less. Life expectancy was very low and what may have appealed to pagans was that the Christian religion and doctrines offered hope and certainty in the afterlife and even some personal divine protection in this world. These new doctrines would have seemed attractive to pagans, when there was growing discontent with pagan practices and a general spiritual unrest. Like Christianity the Roman Religion was for the ordinary man but interest was waning and the mystery religions were far too complicated for the common Roman, thus the people's choice was likely to be Christianity.
Christianity also offered hope to a usually pessimistic society that believed that their destinies were fixed, either to be in the Gods' favour or to be out of it, with no hope of redemption. Christianity offered an alternative with the much desired possibility of salvation.
Christianity was primarily an urban movement, in these urban centre's Christianity grew at a steady pace, the urban areas of cities such as Antioch, were very condensed with people it is estimated that there were 117 people per acre. In comparison to modern cities of today this is rather overcrowded. The overcrowding was so extreme, entire families were living together in single room apartments; this left little personal space and allowed everyone to know each other's business. Given that urban centre's were dramatically overcrowded and that early Roman Greco cities had minimal sanitation or sewerage to the average apartments people would often just throw their bodily waste out the window of their apartments onto the streets. Starks describe the situation in these urbanized areas as:
Given limited water and means of sanitation and the incredible density of humans and animals, most people in the Greco-Roman world would have lived in filth beyond our imagining.
Apartment buildings were often Smokey, dark, damp and always dirty. The air was filled with the smell of sweat, urine and faces. Onto of these conditions the rodents and bugs were everywhere in these apartments. The city streets were not much better they had open sewers, animal manure and crowds in some places it was so bad there were dead human corpses abandoned in the streets. When cities were in a constant state of filth, insects and crowding, disease was rife in these conditions, especially when these Roman societies had no antibiotics or knowledge of germs. Often plagues would strike and physical illness was most likely a part of daily life. An example of this was the analysis of human faeces that were found in a cesspit in Jerusalem showed large amounts of tapeworm and whipworm eggs, which shows poor sanitary conditions where humans often came into contact with human faeces.
Christianity revitalized the way of life in Greco-Roman society offering social change, which dealt with some of the consequences of urban problems. Charity and hope was offered to homeless and the poor, often the cities were full of newcomers and strangers and Christianity offered an extended family and a base for attachments as well as effective nursing services in times of disaster, that were often brought on by plagues, earthquakes and fires.
Christianity's attitude towards society and its social impact greatly resulted in the expansion and success of the church. The church was particularly well-known for its acts of charity, it is likely that the charity itself was one of the most influencing factors to the growth of Christianity.
The church offered this charity to everyone, including pagans and Jews. By the third century the Church was looking after one thousand five hundred widows in need. The church itself was well off and according to Eusebius, by the year 251 the church in Rome supported the bishop, 46 presbyters, 7 deacons, 7 sub deacons, 42 acolytes and 52 exorcists, reader and doorkeepers, but also more than 1500 widows and needy persons. The churches obvious financial stability leads it to be popular and it successfully expanded because it helped those in need, it offered help and often people were converted to Christianity as a result of the kindness and attention they received. Even though the Roman Empire did have some charitable services such as the bread dole, Christian charity far outweighed the state's charity.
Throughout the first century to the fourth century there was government enforced persecution of early Christianity, though not constantly. Persecution and martyrdom became a sign of the strength of Christianity, which often shows if the movement was attracting attention from the Roman state. Such emperors that instigated severe persecution were Decius and Diocletian. There were sufficient amounts of Christians in North Africa for martyrdoms to be noticed, one of these martyrdoms were Perpetua and her slave girl, Felicity who were thrown to the lions after a trial.
Tertullian wrote that "the blood of Christians is seed" which is often misquoted as "the blood of the martyrs is the seed of the church." Tertullian may have been saying this because he believed that martyrdoms created new converts or may have strengthened the church.
The Roman Empire wanted to exterminate this new religion as quickly as possible and it seems it tried in the beginning to exterminate every Christian they could find but later under Decius they started new methods to try and exterminate Christianity one way was by removing the clergy and the bishops and also taking away lands and churches from the Christians, irrespective of rank while forcing them to sacrifice to the states pagan gods or be punished severely with torture, exile, slavery and sometimes execution, depending on numerous reasons and the time of persecution.
This would have had to give this new religion much publicity, especially if it was in the circus arenas being killed by wild beats would have been creating attention, it seems many would have seen these peculiar people willing to suffer excruciating torture and even die for their God and religion, this must have left the pagan with something further to think about and consider if they were willing to die for their pagan gods.
The Christians may even have won converts in some areas, because of their courage during the persecutions, the strength of their faith and the support they showed one another, Tertullian said that pagans had exclaimed in the arenas during martyrdoms "See how these Christians love one another" this indicated the social nature of the Christian faith. The persecutions also created apologists these were people who would be writing trying to convince the authorities they had done nothing wrong, whether or not the Emperors read these long letters of apology no one knows, it seems rather unlikely however one could suggest State officials having read these letters of apology.
Another aspect of Christian growth was that Christianity and its friendships formed from within the Church lead to its successful growth because those who had become a Christian felt that they were to fulfil the great commission as taught by Jesus and the apostles and they were to pass the message onto their friends and family, this quite often led to a close knit community and this was appealing in an era when it was expected of you to look after yourself. In this Greco-Roman era religious and social life was very much interlinked. It was taught in the church that if Christian travellers came from outside of the city or were strangers to a new city, Christians were to provide their needs and provide shelter to these Christians, this was not only taught in the teachings of Jesus but also by the apostle Paul. So it was an incentive to be a Christian as there was always help and social networks that could support you in a large empire. It was like an extended family where ever you went in the Roman Empire. Eusebius writes that the Christian missionaries were so inspired by the Holy Spirit that they saw mass conversions occur, this may also be a contributing factor.
Christianity also gained some favour in society because of its improvement in the treatment of women, and it elevation of their social status. Christianity taught that marital unfaithfulness in one partner as serious as in the other and that in according to the New Testament, husbands should treat their wives with such consideration and love as Christ manifested for his Church, though women were still considered homemakers and wives. It is believed that Christianity made its way into the aristocracy in Rome at the time through the influence of their wives.
The Greco-Roman world was quite different woman had far less rights than men. It was a very male orientated society where male babies were wanted and female babies rejected this resulted in infant side of female babies. Some excavations have found hundreds of babies bones in an underground sewer thought to be female babies. It was not uncommon that girls were offered in marriage before they had reached puberty to much older men and the cultural custom was that the women were the property of the man, either the father or the husband. Women played a big role in the early Christian church this may have been because they received more rights in the Christian community when compared to women in the Greco-Roman world. We see in some early writings in regards to the persecution of Christians that many more females clothing were stored or found than men's, more than double, this may suggest there were far more females than males in the early church.
If this is true that there were far more females than males in the early church then that allows for many secondary conversions. Secondary conversions are ones that are a result of someone else being converted because of the first conversion, for instance a woman is converted but then shortly after her husband is converted which most likely would not have occurred if the woman was not originally converted. Christian doctrines were against abortion and infanticide. This may have had some effect on the birth-rates of Christian woman compared to their pagan counterparts.
The spread of Christianity also involved Christian writings by the end of the first century the writings of Paul and the apostles of Jesus had been spread sporadically through the Roman Empire. Apart for the early apostolic writers, others set about advocating, defending and propagating Christianity. Justin Martyr who lived around Ad 100-160 was a Christian teacher and philosopher, he wrote the first and second apology. There were many subsequent Christian writers throghought the early years of the church, most often they were well-educated, such as Origen, Tertullian and many others. In the pagan mystery religions only the elite could read the sacred and secret texts, however in Christianity often the Gospels and Paul's epistles were read out aloud for all to hear in the church, this may have appealed to the pagans when considering a choice in further religious observance. The Christian writings also acted as a means of spreading the Gospel message from place to place, often reaching further than the Roman Empire itself.
Overall there are many factors that contributed to the success of the church. The caring for widows, the poor and the sick, the Christians attitudes to death, when faced with martyrdom, better equality among women and men and the treatment of slaves, all this made an impact on society were these things were rare. Christianity was less likely to succeed by any ordinary standard of expectation however it did through the Christian application of charity and its simple guide to salvation. We cannot say or point to one cause and say it was the sole reason why Christianity was a successful religion; the causes mentioned build a substantial cumulative case for the rise of Christianity.