(Adapted from Harris, The New Testament; Einhorn, The Jesus Mystery)
Although he never met Jesus or witnessed any of the events of his life, and once mocked and persecuted Jesus’ disciples (he was, after all, a Pharisee as well as a Roman citizen and therefore a sworn enemy of Jesus), within a year or two of Jesus’ crucifixion on the road to Damascus he experienced an epiphany (spiritual vision) of the risen Christ that transformed him into the most influential figure of early Christianity. He was almost single-handedly responsible for transforming a Jewish sect into a world religion.
While the other three “pillars” of the early church – Peter (Cephas), James (the brother of Jesus), and John – remained in Jerusalem to convert the Jews, continuing to emphasize the importance of Torah observance, the focus of Paul’s ministry (even though he was a circumcised Jew of the tribe of Benjamin) was on the Gentiles and he preached the total irrelevancy of Torah observance: salvation is by faith, not by works.
He spoke and wrote in Greek, though it may not have been his mother language, and was equally fluent in Hebrew and Latin. Nearly one-third of the New Testament is ascribed to him (14 letters, although most scholars regard only 7 as genuinely Pauline):
By Paul 1)I Thessalonians – Young church doing very well; Timothy has checked on them and found no major disputes or controversies. 2)I Corinthians – Many quarrels and factions, peculiar idea of baptism, challenges to Paul’s authority, Christians suing one another, some members visiting prostitutes, suggestion of incest. Paul gives balanced advice. 3)II Corinthians – Paul savagely attacks pseudo-apostles in the church who challenge his authority and form their own doctrines. 4)Galatians – Explosive, sarcastic rebuke of Christians who have capitulated to outside Judaizers. A declaration of independence from Mosaic Law and the influence of the synagogue. 5)Romans – Longest of Paul’s letters, sent in advance of a visit. Deals extensively with Jew/Gentile controversy. Letter was possibly intended to circulate among a number of churches. 6)Philemon – A private letter, raising the issue of Philemon’s escaped slave, whom Paul has come to love in prison. 7)Philippians – Written from prison. Paul has great affection for this church. Probably Not by Paul 8)II Thessalonians – A controversial letter: parts are similar to I Thessalonians but other parts express contradictory theology. 9)Colossians – Paul never went there. Central purpose of letter is to combat a deviant form of Christianity. Definitely Not by Paul 10)Ephesians – Not written to Ephesus (Paul spent two years there). Letter addressed to people Paul did not know personally. A forger appears to have used Colossians as a model for Ephesians. 11)I Timothy – I and II Timothy and Titus are manuals for church officers to standardize church practice 12)II Timothy – see above 13)Titus – see above 14)Hebrews -- Even early Christians did not believe Paul wrote Hebrews.
Paul remained celibate, even though it was extremely unusual for a Jewish male from a Pharisaic family to be unmarried after age 20 and the pressure to get married in Jewish culture was extremely strong (cf. the Talmud: “One who reaches the age of twenty and has not married lives all his days in sin”). A man who reached the age of 20 and was still unmarried could be forced by the courts to marry. (Note that Jesus too was unmarried at the age of 30.)
We learn some things about Paul in Acts, but much of this biographical material – that he was originally called Saul, that he was born in Tarsus (in modern Turkey), that he studied under the famous Rabbi Gamaliel, that he practiced the trade of leather worker or tent maker – is not confirmed by Paul himself in his letters, and some statements about him in Acts are contradicted by his own statements in the epistles. The author of Acts seems unaware of Paul’s epistles, his claims to apostleship, and his core message – that man is saved by faith and not by Torah observance. The book of Acts ends abruptly with Paul under house arrest in Rome; we are not told what became of him, but according to legend Nero beheaded him. (Nero himself committed suicide in 68 CE.)
Paul, for his part, seems largely unaware of Jesus’ life and teachings.  His worldview is centered on the crucifixion and resurrection – proven to him by his vision of the risen Christ on the road to Damascus. Although he did not meet the standards set by the first generation of Christians for apostleship (an apostle was one called by Jesus as a disciple and who witnessed the risen Christ), he insisted that he was a true apostle on the basis of his personal vision on the road to Damascus. 
Paul’s conversion occurred in c. 32-33 CE. He spent the next three years in Arabia (we are not told what he did there). He returns to attend a conference in Jerusalem. We next meet him when Barnabas calls him to go to Antioch (45-46 CE). We aren’t told what happened in the intervening years, or why 15 years elapsed between his conversion and his first missionary journey.
Paul’s theology was not systematic but occasional, i.e., a response to specific situations. He never ceased to believe that “the end is near,” which accounts for the urgency of his message. He believed that man was totally depraved, but justified by faith in Christ. Salvation was the result of faith, not works. The law of love makes Mosaic Law obsolete. He stresses God’s redeeming grace and sanctification by the Holy Spirit. 
The apocryphal Acts of Paul and Thecla (c. 200 CE) provides a physical description: “And he saw Paul coming, a man small in size, with a bald head and crooked legs; in good health; with eyebrows that met and a rather prominent nose; full of grace, for sometimes he looked like a man and sometimes he looked like an angel.”
Paul was candid about his shortcomings, acknowledging his unprepossessing physical appearance and his speaking skills, which apparently left much to be desired. He also speaks of an unidentified “thorn in the flesh” (sometimes translated “a sharp physical pain”) that he strove to overcome. He lost his temper on not a few occasions. He could be egotistical, self-pitying, stubborn, and defensive. Paul’s defensiveness seems to stem from three biographical facts:
a)He had a past as a Pharisee and persecutor of Jesus and his followers b)He was not an apostle as apostles defined the term c)He was not a member of the Jerusalem inner circle of church leaders
That said, his spiritual gifts were legendary. As a Pharisee, Paul had been tireless in his Torah observance. As a converted Christian, his personal energy continued unabated, as evidenced by his exhausting travel schedule (he made five separate multi-city missionary journeys), his prolific writing, his emotional intensity, and his brilliant mind.
For a chronological sequence of Paul’s life, see Harris, The New Testament, p. 308.
 Nor is Paul mentioned in any of the gospels, which were written long after his death. In I Thess. 1:5 Paul uses the term ‘gospel’ 20 years before the first gospel (Mark) was written.
 Paul refers to this experience in the epistles but never describes what actually happened.
 Many have seen the Protestant Reformation as a revival of Pauline theology. The Roman Catholic Church came to emphasize good works and church ritual. Paul treated both with contempt.
 Paul’s “thorn in the flesh” has been variously identified as lameness, poor vision, epilepsy, and homosexuality, but these are all guesses.