My Understanding of the Factors that Led to the Rapid Rise and Eventual Success of Christianity:
I think there were several factors that predisposed Christianity1 to rapid, widespread growth.
It began near the nexus of 3 continents: Europe, Asia, and Africa.
It began during the Roman Empire, while the Empire was still relatively strong and robust, and controlled much of Europe and the Mediterranean, including North Africa. It had access to an extensive network of roads, and it had never been so easy to travel great distances. In Paul's letter to the Romans, he says he is planning a trip to Spain. He traveled throughout Asia Minor, Palestine, Greece, Macedonia, etc. By our modern standards, this wouldn't be very impressive, but this was happening 2,000 years ago, when the closest thing to an airplane was a horse,
After the message was altered to make it less Jewish in nature, it became fairly inclusive.
It was relatively unique in that it was a religion of belief rather than mere observance.
It was also relatively unique in that it made promises of eternal rewards for the people who had been denied rewards in life.
It was evangelical, and some of the apostles were brilliant PR men.
Shortly after Jesus died, the new movement began to alter his message. This process has continued to this day, although at a much less drastic rate after the first couple of centuries. This is a huge benefit because it allowed the early church to become whatever its congregants needed it to be.
- For example, the religion is based on a devout Jewish itinerant preacher who lived under Roman occupation and wasn't very happy about it. The Romans brutally murdered him in an unimaginably horrible way, and as his followers attracted new converts, the Romans persecuted them. Yet the church leaders in the second, third, and fourth centuries were able to take this faith based on an outspoken critic (and victim) of Rome, and turn it into the official religion of the Roman Empire. Later, beginning in the Middle Ages, this religion based on a Jewish preacher became the biggest contributor to the spread of virulent anti-Semitism throughout Europe. These are remarkable transformations, and they demonstrate just how adaptable Christianity was.
It became a religion of the book very early on in its history.
A More In-Depth Explanation:
Jesus probably died around the year 35 CE. Paul was writing his letters, epistles, and homilies only 20 years later. Unfortunately, he never actually met Jesus, and his letters tell us almost nothing about the living Jesus, whom Paul describes almost dismissively as "Jesus-in-the-flesh". If you go through all of the letters known or widely believed to be written by Paul, and write down everything he says about Jesus' life, you will be shocked to find that all the relevant passages will fit on a single index card.
Still, there are few people as important to the rise of Christianity as Paul. He was apparently quite charismatic, and people paid attention to him. He had previously been a Pharisee, or a devout, zealous, almost militant Jew, and had been an active participant (and according to his own testimony, a leader) in the persecution of Jesus followers in Jerusalem after Jesus' death. After his famous conversion experience on the road to Damascus, he did a complete about face. Rather bizarrely, he now preached of the redundancy of Judaism, and urged his flock not to become Jews in order to follow Jesus. This didn't go over well with the disciples, who were well aware that Jesus was an extremely Jewish man, and had preached almost exclusively to Jews. Paul came into conflict with the disciples many times, and he wrote surprisingly hostile things about them in his letters. But despite the fact that he almost certainly turned Christianity into something totally different from what Jesus had in mind, he set the stage for its later success.
Paul would go to a new town, set up a shop (he is believed to have been a leatherworker of some sort), and talk to his customers as he worked. After a few weeks, he would leave for the next town, but he would also check in with the churches he had already created, usually by writing a letter, but if he heard something that worried him, he would send a trusted assistant to set things straight. If that didn't work, he would go back himself and read his congregation the riot act. Eventually, his constant clashes with the disciples, and their attempts to go behind his back to dissuade the Pauline churches of Paul's bizarre form of Jesus following, led Paul to go somewhere far enough away from Jerusalem that the disciples would not be able to interfere with his self proclaimed mission. He went to Rome, and after that we hear nothing about him, except that he was apparently crucified some years after he arrived. But his letters lived on, as did his influence on the Christian faith.
After Paul wrote the earliest letter which is still extant today, it was another 15 to 20 years before anyone wrote anything about Jesus. Fortunately, this time someone wrote his life story. The first gospel to be written was the one we know as *The Gospel According to Mark*2, which most scholars date to 65-70 CE. Matthew and Luke were probably written between 85-95 CE. In fact, Matthew and Luke may have been writing at the same time as one another, and it is clear that both had access to the Gospel of Mark, but Matthew and Luke didn't know each other and neither had seen the other's gospel before writing his own. John was written much later; scholars usually date it to between 90-110 CE. Although none of these men ever met Jesus, and aside from Paul, they may not have met anyone who had met Jesus; John almost certainly didn't meet anyone who knew Jesus.
Still, the crucial fact remains: within 80 years (at most) of Jesus' death, all four gospels and the genuine Pauline Epistles, Homilies, and Letters had been written. Even better, the religion was still a small sect within Judaism, which meant that people who decided to follow the "Jesus Movement" (as modern scholars have dubbed it) also had access to the Jewish bible, (or at least most of it). From the beginning of Christianity's rise, it enjoyed the benefits of having written scriptures to make sure everyone was on the same page, so to speak, and this made it much easier to spread the word. In all honesty, the Christian church owes all the credit for this to Judaism - unlike the vast majority of religions in the ancient world, Judaism had a book, long revered, set in stone, orthodox and canonical, and they passed this blessing on to the Jesus Movement.
It is remarkable that, as Christianity slowly spread, and people began to write their own versions of the Jesus story, the gospels we know from the "NT" of the Christian bible were widely recognized as superior to most of the other Christian texts. There were many exceptions, of course, and nebulous forms of the faith, such as Christian Gnosticism, rejected some or all of the gospels which ended up being canonized. But still, on the whole, the most popular scriptures seem to have been the one that made it into the final compilation we call the bible. This was a tremendous asset, because as more time passed after Jesus' death, and everyone who knew him died as well, the leaders of the nascent church were able to point to the gospels and demonstrate the authenticity of the creeds and dogmas which had begun to spring up.
The church grew, but slowly. As the number of Christians increased, the pagans among whom they lived became suspicious. These people don't make the proper sacrifices to the gods of the Roman Pantheon! They don't offer incense and meat to Jupiter on the day of his festival! They worship in private and keep apart from us! They must be doing something deviant and awful! The pagans would go to their local procurator, governor, or proconsul, and insist that something be done to deal with this menace. The politicians were only interested in securing their own positions, so if allowing a massacre of Christians would keep the majority of the population happy, so be it!
Only much later did persecution of Christians become a policy of the Empire, and even then, it was carried out in a piecemeal, sporadic fashion. In most cases, it was not the government, but the common people who instigated violence against Christians. But then came Constantine. He converted to Christianity (probably as much from political self interest as from genuine devotion), and although he didn't make Christianity the official religion of the Empire, he did abolish several laws which had persecuted Christians, confiscated their property, and made life miserable for them. A later Emperor reinstated the laws, but they were abolished permanently soon afterward, and Christianity finally became the religion of the Roman Empire.
This was arguably the most significant event in the early history of the Christian church. The bulk of the continent of Europe was now Christian, and in future centuries, Europe would come to dominate the globe in terms of political, economic, trade, and military power. From this base, Christianity would spread around the world, and become the most popular religion in human history.
At first, there was no homogeneity among Christians. For this reason, the Biblical scholar Dr. Bart D. Ehrman, and many of his colleagues, prefer to talk of "early Christianities", not "early Christianity". It would only be a slight exaggeration to say that each Christian during the first century had their own version of the faith. This was dangerous, since a cohesive movement is more likely to persist than a nebulous, incoherent one. Some shrewd political minds began to realize that the movement(s) needed someone at the helm, to figure out the right way to be a Christian. So began the Christian church.
By the third century, the group scholars refer to as the Proto-orthodox Christians had taken command, marginalizing and eradicating sects they deemed heretical. The Gnostics, Ebionites, Marcionites, Arians, and many other sects were effectively destroyed by the manipulations of the self described "Church Fathers". Their scriptures were burned, and our only copies of these texts come from impossibly lucky finds in caves, garbage pits, graves, and the ruins of ancient monasteries.
This narrowing of Christianity is lamented by curious scholars, because so much was lost forever; however, it probably played a significant role in ensuring that Christianity would become the most popular religion in human history. By closing the door on every other form of the faith, they made Christianity a monolithic entity, with people in positions of power to steer the course and keep it on track. The proto-orthodox Christians became the Orthodox Christians, but later split into three distinct factions: Eastern Orthodox, Catholic, and Protestant. Every extant form of Christianity can trace its roots back to the proto-orthodox.
Just How Fast Did Christianity Grow?
The sociologist Rodney Stark wrote a book called The Rise of Christianity: A Sociologist Reconsiders History, or How the Obscure, Marginal Jesus Movement Became the Dominant Religious Force in the Western World in a Few Centuries. He found that during the first three and a half centuries of its existence, Christianity grew at a steady rate of 40% per decade, or 3.42% per year3. This trend ran out of steam shortly after the death of Emperor Constantine, but only because there weren't enough people to continue the trend.
Constantine became Emperor in the year 306 CE. His conversion began in 312 CE, and he died in 337 CE; during his reign, the population of the Empire was roughly 60 million people. According to Stark, in 300 CE, the Christian population of the Empire was about 6.3 million, or roughly 10.5% of the total population. By 350 CE, only 13 years after Constantine's death, there were nearly 34 million Christians in the Empire, accounting for 56.5% of the total population.
The Rise of Christianity, Chapter I: Conversion and Christian Growth' Rodney Stark, p. 13
The 40% per decade trend ended around 350 CE, because there simply weren't enough people for the trend to continue - if it had, there would have been nearly 190 million Christians in the Empire by the year 400 CE, which would be more than three times the total population of the Empire. Suffice to say that by 400, or 450 at the latest, virtually everyone in the Empire was Christian.
Today, there are well over a billion Christians in the world, and no religion has ever been so influential in shaping the course of human events, for better or worse.
Stark points to a number of advantages that Christianity had over paganism to explain its growth:
While others fled cities, Christians stayed in urban areas during plague, ministering and caring for the sick.
Christian populations grew faster because of the prohibition of birth control, abortion and infanticide. Since infanticide tended to affect female newborn more frequently, early Christians had a more even sex ratio and therefore a higher percentage of childbearing women than pagans.
To the same effect: Women were valued higher and allowed to participate in worship leading to a high rate of female converts.
In a time of two epidemics (165 and 251) which killed up to a third of the whole population of the Roman Empire each time, the Christian message of redemption through sacrifice offered a more satisfactory explanation of why bad things happen to innocent people. Further, the tighter social cohesion and mutual help made them able to better cope with the disasters, leaving them with less casualties than the general population. This would also be attractive to outsiders, who would want to convert. Lastly, the epidemics left many non-Christians with a reduced number of interpersonal bonds, making the forming of new one both necessary and easier.
Christians did not fight against their persecutors by open violence or guerrilla warfare but willingly went to their martyrdom while praying for their captors, which added credibility to their evangelism.
Stark's basic thesis is that, ultimately, Christianity triumphed over paganism because it improved the quality of life of its adherents at that time.
1 In the beginning, people who followed Jesus weren't called Christians. In fact, we don't know if they were called anything in particular. During Jesus' lifetime, he and his followers were simply Jews. This was still the case for all of his followers for another couple of decades at the least, and most of them probably consider themselves exclusively Jewish as long as they lived. It was only in the second and third generations of Jesus followers that the slow but steady drift away from Judaism began. Some small sects of Jewish Jesus followers remained active until perhaps the fifth century or later. This situation cause problems for scholars, who like to have specific names for things. Therefore, the most popular term for the first followers of Jesus are now known as "The Jesus Movement". It bears repeating that these people were completely Jewish in belief, practice, and self identification. Furthermore, non-Jews also considered these people to be Jewish. It isn't clear when the Roman government began to notice the difference between regular Jews and Jesus Jews, but it is known that they had begun to single out Christians (who were by this time really Christians) by about a hundred years after Jesus died.
2 As far as modern scholarship has been able to determine, there is probably no reason to believe that the authors of the gospels were named Matthew, Mark, or Luke. There is a possibility that the author of some sections of John was actually named John, but the traditional claim that this was John the Beloved Disciple is not taken seriously by most impartial scholars. The earliest manuscripts of the gospels don't have any names attached, and there is no evidence that they were called by the names we know until a century or more after they were written. These names were attributed to them by the early leaders of the church, and some records remain of some of these leaders expressing their doubts about the issue of authorship.
3 Interestingly, the Mormon church has grown at a rate of 43% per decade for the last century.