What is Pre-Christendom?
Pre-Christendom is the era of Christianity lasting from the time of Jesus until 312 C.E. when the Roman Emperor Constantine became a Christian. It is called Pre-Christendom because it preceded the Christendom era, the years when Christianity was at the center of Western culture.
In the years following the life of Jesus, Christianity was considered little more than a sect. Many believed it to be a version of Judaism. In fact, many Christians considered Christianity to be an extension of the Jewish faith because the person in whom the early believers had put their trust was the Jewish Messiah.
Sadly, Christianity was intensely persecuted during those Pre-Christendom years. Nevertheless, Christianity spread. By the time Constantine became a Christian in the early fourth century, “five to six million people—between 8 and 12 percent of the imperial populace—were Christian.” 
That’s a huge number! In order to reach that number, it is calculated that the Pre-Christendom church had to grow at a rate of forty percent per decade!
How did the Pre-Christendom Church Grow so Fast?
Despite the fact that the Pre-Christendom church grew at an incredible rate, there are no records of any kind of mission strategy. Unlike twenty-first century church growth strategies, “the expansion of the churches was not organized, the product of a mission program; it simply happened.” 
It seems that the early church did not think in terms of church growth or even Kingdom growth. They didn’t try to plant the biggest church in town, nor did they try to have the best programs and ministries to get people interested in attending their churches.
Focus on Faithfulness
Instead, the Pre-Christendom church’s highest priority was to be the hands and feet of Jesus in the world. One of the strongest arguments against the Pre-Christendom church in those early centuries was the fact that Christians regularly associated with the dregs of society—the poor, the diseased, slaves, and so forth. It seems many who were outcast and marginalized were attracted to Christianity because they found a place where they were loved and welcomed.
Consider Emperor Julian (who was actually Constantine’s nephew and tried to restore Rome’s paganism) who said this:
It is disgraceful that, when no Jew ever has to beg, and the impious Galilaeans [Christians] support not only their own poor but ours as well, all men see that our people lack aid from us.
Julian was frustrated that Jews and Christians were caring for the Roman pagan poor. Following this statement, Julian goes on to say that the Roman pagans should care for the poor so that they don’t all convert to Christianity.
How did Pre-Christendom Christians Get Like This?
But here’s the question. How did Christians get to be like this? How did they become the kind of people who welcomed anyone? Why were they so open to the outcast and marginalized?
The fact is, the Pre-Christendom church didn’t pursue church growth. They didn’t put together a mission strategy. What the Pre-Christendom church did was prioritize the spiritual formation of those who put their faith in Jesus.
A Life Like Jesus
Getting people to put their faith in Jesus was not the goal for the Pre-Christendom church. Coming to faith was certainly an important step in the spiritual journey of an early Christian. But “getting saved” was not the end of the journey.
The goal for each person in the Pre-Christendom church was to become like Jesus. After a person came to faith, they would enter a long process of spiritual formation. As they became more like Jesus, they became more compassionate, more generous, more honest, more just. It was these qualities in the followers of Jesus that drew so many to this new and unique way of life.
So, how did the Pre-Christendom church grow so dramatically? By focusing on the spiritual formation of the followers of Jesus.
 Kreider, Alan. The Patient Ferment of the Early Church. (2016: Baker Academic, Grand Rapids), p. 8.
 Kreider, Alan. The Patient Ferment of the Early Church. (2016: Baker Academic, Grand Rapids), p. 9.