By Bart D. Ehrman, The University of North Carolina, Chapel Hill
Paul’s importance to the early Christian movement can be seen in three areas. Firstly, in terms of the New Testament itself, in which 13 out of the 27 chapters were written by Paul. Secondly, in his role in Christian mission by being the most important missionary. And thirdly, in his spreading the idea of Christian theology more than anyone else.

The New Testament
The New Testament is the very bedrock of the Christian tradition, whichever form of modern Christian faith one thinks of, Roman Catholic, Eastern Orthodox, Protestant.
There are 27 books in the New Testament, 13 of them claimed to be written by Paul. One other book, the book of Hebrews was included in the New Testament because Church fathers (wrongly) considered it to be by Paul, even though it doesn’t claim to be written by him. One other book, the book of Acts, is largely written about Paul. That means that 15 of the 27 books are, in one way or another, directly influenced by Paul.

Paul and his Jewish Faith
Paul himself tells us that he was born and raised Jewish, that he was extraordinarily passionate about his Jewish faith, and that he was committed to the Phariseesaic way of interpreting the law in a very meticulous way.
He says that he was better versed in the traditions of the Pharisees than any of the people his own age. Based on the fact that he was a Pharisee and then on everything else he says, it’s clear that like so many other Jews at the time, Paul was apocalyptic in his views.
Paul’s Conversion
Before being a follower of Jesus, Paul thought that the world was controlled by powers of evil and that God was soon to enter into judgment with this world to destroy everything that was opposed to him before bringing in a good kingdom to earth, something very similar to what Jesus thought. Paul indicates that when he first heard about the earliest Christians, he became intent on destroying their faith.
Unfortunately, he doesn’t tell us how exactly he was going about doing it and what his persecution entailed. Moreover, he never explains exactly why he found the Christian message so offensive, but he does give us some hints. It appears that he considered the very central claim of Jesus’ followers to be completely ludicrous—the idea that a man crucified by his enemies was God’s powerful messiah.
For most Jews, this was just the opposite of what was supposed to happen to the messiah. He was supposed to destroy the enemies, not be tortured to death by them.
But then something happened; a complete turnaround that altered the course of history. From the time frame that Paul himself sets out in his letters, it appears that his conversion must have occurred something like three years after the death of Jesus.
This article comes directly from content in the video series The Triumph of Christianity. Watch it now, on Wondrium.
A Sect Within Judaism or a World Religion?

Paul’s second important role in early Christian movement was in terms of Christian missions. Christianity started out as a tiny sect within Judaism, made up of Jews from the remote rural area of Galilee who believed Jesus was the messiah. It became a religion spread throughout urban areas of the Roman world all within decades.
Paul appears to have been the most important missionary of the earliest Christian movement, determined to spread the faith throughout the entire world to give all people a chance to convert before the end of history arrived. Without Paul, it is not clear whether there ever would have been much of a Christian mission.
The Theology of the Early Christian Movement
The third important role played by Paul was in terms of Christian theology. Contrary to what is often said, Paul was not the first to say that salvation comes only by Jesus’ death and resurrection. Others were saying that before Paul; in fact, Paul was persecuting the Christians before he himself became one. He was persecuting them because they talked about Jesus’ death and resurrection as the messiah. Even though Paul did not invent that idea, he developed it more than anyone else we know of.
For the spread of Christianity, Paul actually came up with the corollary that made all the difference. The reason this religion could spread at all is that it shifted from being a belief of a group of Jews in the Jewish messiah to being a worldwide religion for both Jews and Gentiles.
It was Paul, more than anyone else, who promoted the idea that salvation, as brought by Christ, did not require a person to first adopt the ways of Judaism. That may seem blindingly obvious to most Christians today, but it was not at all obvious in Paul’s day. Once he reached this conclusion, he promoted it with rigor, especially with other Christians who either didn’t agree or had serious doubts, including some of the original disciples.
Common Questions about Paul’s Influence on the Early Christian Movement
The New Testament is made up of 27 books. 13 of these books are claimed to be written by Paul while another was wrongly claimed to be written by him. Also, the book of Acts heavily revolves around Paul’s missionary life. So, about 15 out of the 27 books that make up the New Testament have been influenced by Paul one way or another.
Paul believed that the world was controlled by agents of evil and that God would step in and destroy all evil so a good kingdom could rise. Before he became part of the early Christian movement, the idea of God’s messiah being crucified was, to an extent, offensive to him since the messiah was expected to destroy evil, not be killed by it.
Paul’s mission helped the early Christian movement spread throughout the Roman world since he was determined to give everybody a chance to convert to Christianity. He was responsible for taking Christianity from being a religious sect within Judaism to being a religion of its own.