The man we know as St. Paul was Paul of Tarsus. He is not a saint that everyone has felt comfortable. Many find him harsh, difficult and uncompromising. This is true not only, now but was so in the case of his early associates and later with the other saints of the Catholic Church including St. Peter, St. Mark, and St. Barnabas. The gentle St. James once even advised him to be more diplomatic and tactful. Still at the end of it all the other saints came to look upon him with reverence and affection and so is the case with anyone who gets to know him by the study of his epistles and the Acts of the Apostles. He is a person with an indomitable spirit, filled with so much of loyalty and affection for his friends that finally he removes all criticism and his tough exterior falls away to reveal and individual so full of humanity and holiness in his every breath. Tarsus is his birthplace and is a rich university city located in Asia Minor. His parents were Roman citizens and so of good standing. His upbringing was under the strict Pharisee tradition and learnt Jewish theology under the famous Rabbi Gama'iel. He was set on a path to achieve great things and set out with the expectations of everyone that he would fulfill this to Jerusalem approximately a year after the crucifixion of Christ.
Paul was present during the martyrdom of St. Stephen and would have heard him pray for his murderers and probably that prayer was answered, when shortly afterward as Paul proceeded to Damascus he had a blinding vision of Christ that turned him away from being a persecutor of Christians into a leader of them. Yet there was to be an elapsing of time before he started to his play the role that was required of him. Soon after he was baptized St. Paul retired to the desert and spent two years in meditation and then returned to Damascus. It would take three years before St. Paul proceeded to Jerusalem to meet up with the Apostles, after which he retired once again to Tarsus. Thus there is a span of ten years during the years 34 AD to 44 AD during which St. Paul remains out of sight and probably during this time with God by his side and his intellect to help him he built the bridge between Christianity and Judaism, Gentile and Hebrew, which remains one of his greatest contributions. This does not mean that St. Paul was the first to baptize a non-Jew. That credit goes to St. Peter and St. Phillip.
The systematic approach of preaching to non-Jews started only towards the early 40s of the first century and St. Barnabas who was commissioned for this purpose sought the services of St. Paul who was forgotten at Tarsus and managed to convince him. St. Paul came back with him to Antioch and from that time immersed himself in missionary work and spreading the word of the Lord. The scholar and thinker had changed roles to that of teacher and preacher. (St. Paul) The historical records available on St. Paul far outnumber any other Scriptural saint. The important among these are the fourteen letters of St. Paul included in the New Testament and St. Luke's Acts of the Apostles. It is often considered that of all the founders of the Church St. Paul was the most brilliant and multi-dimensional and with the broadest outlook. He was therefore the best equipped to spread Christianity into different lands and to different people.
The Catholic Church as an institution came into existence when Emperor Constantine the then Roman Emperor accepted Christianity and Rome became the Holy Roman Empire. This was a gigantic step on the road to the growth of Christianity and was based on the work initiated by St. Paul. St. Paul had traveled to Rome to become a key figure in the attempts to establish the Church of Rome, which finally has become the Roman Catholic Church that we know today. It was St. Paul that brought about the concept of evangelism. In this he preached that only when the whole world was converted to Christianity would Jesus return as prophesied in the Bible. Many hundred years later the first big step in this direction was achieved when the Holy Roman Empire was created as Rome ruled most of the known world then. In the early centuries after the death of Jesus Christ, a church was considered to be a gathering of people around a bishop. The structured existences of Churches are a later development. These local churches gradually united and were grouped around the larger and more prominent centers. The bishops of these larger centers also gradually became more prominent and this way the grouping of churches became larger and gradually developed rituals of their own. Yet all of them can trace their origin and founding to Jesus and his Twelve Apostles and St. Paul clearly spells this out in his opening lines of the Corinthians.
The monumental work of St. Paul is seen in the world wide spread of the Christian Church. He was not the first to start preaching as we have seen, yet it was his firm stand in defeating the Judaizing party that was responsible for the future progress. Without any doubt it is to St. Paul's credit more than anyone else's that Christianity which was a small sect in Judaism grew in stature to become the most spread religion in the world. The influence of St. Paul did not end with his death but continued. This can be seen in the Pastoral letters written to Timothy and Titus in his name to promote fidelity to his teaching in all probability some time around the end of the first century. Simultaneously the letters of St. Paul that had survived were collected for general circulation and these very soon became the standard of reference for Christian teaching. If we look at the theory of atonement, whereby the salvation of man and return to God happened through the sacrificial death of Jesus Christ, we will find that this heavily relies on St. Paul. The effect of St. Paul is most profound on history of the western half of Christianity due to the writings of St. Augustine. The Pelagian controversy in the context of grace and free will required the turning to the interpretation of the passage in St. Paul's letter to the Romans.
In presenting a case in favor of the necessity of divine grace for salvation, St. Augustine built on St. Paul's theory of predestination and correctly interpreting this theory as a reference to God's predestined plan of salvation of mankind and as a concept that did not have to clash with the freedom of one to exercise his will. The Reformist movement of the sixteenth century has also based a lot of their justification on St. Paul and therefore is deeply indebted to him. Martin Luther utilized the doctrine of justification by faith and drew a difference between faith and works and used this as the foundation of his attack on the late medieval Catholic Church in Rome. John Calvin fell back on St. Paul to lay the basis of his theory of the church as a company of the elect and used the idea of predestination. He also added that predestination to salvation for the elect only. Thus the teachings of St. Paul passing through the influence of St. Augustine had a profound effect on the Reformation and what it left back in the form of the Lutheran and Calvinist Churches.
However such a prominent effect of St. Paul's teaching are not present in the Eastern Orthodox Churches. Current day research has tried to probe behind these controversies in an attempt to see St. Paul in the correct context of his responsibility in the spread of Christianity. Once the foundation of St. Paul's line of thought in respect to Jewish concepts during his time are understood as brought out by current day studies the rigid pedestrian views of some of Calvin's followers are found to be a too uncompromising interpretation of what St. Paul meant. The attempts to try and derive thoughts from Greek or Gnostic have been given up. We see St. Paul more in the light of a Christian Jew whose experience with God that led to his conversion made him fully realize that Christ was the Universal Lord under God, the agent and ruler of his father's kingdom. Thus it is that St. Paul maintains that it is only through Jesus Christ that every impediment is broken down and man is all the same through the union wit Jesus Christ and puts this very clearly in his words "There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female: for you are all one in Christ Jesus" (Gal. 3:28)