Over the years I have had my share of discussions about what we can know about Jesus. I think a good starting place about historical discussions about Jesus is seen in the book The Resurrection of Jesus: A New Historiographical Approach by New Testament historian Mike Licona. In the book Licona discusses what is called “The Historical Bedrock.” These three facts about the Historical Jesus are held by most critical scholars and historians:
1. Jesus’ death by crucifixion
2. Very Shortly after Jesus’ death, the disciples had experiences that led them to believe and proclaim that Jesus had been resurrected and had appeared to them.
3. Within a few years after Jesus death, Paul became a follower of Jesus after a personal experience that he interpreted as a post resurrection appearance of Jesus to him.
In this post, I want to focus on #3. After all, Paul wrote a large majority of the New Testament. Also, his letters are the earliest records we have for Jesus.
Well known New Testament scholar Dr. Bart Ehrman writes the following regarding Paul’s experience:
It is a historical fact that some of Jesus’ followers came to believe that he had been raised from the dead soon after his execution. We know some of these believers by name; one of them, the apostle Paul, claims quite plainly to have seen Jesus alive after his death. Thus, for the historian, Christianity begins after the death of Jesus, not with the resurrection itself, but with the belief in the resurrection” 
Even New Testament scholar Dale Allison even says that Paul converted from a persecutor of the church to one of its greatest promoters because of an experience he perceived was of the risen Jesus appearing to him.  Note: see more below on the issue of whether Paul “converted.”
Some Background on Paul
The undisputed letters of Paul that can be used to give us an understanding about who he was and what his mission was are in Romans, 1 and 2 Corinthians, Galatians, Philippians, 1 Thessalonians, and Philemon. The rest of the letters yield very little about the life of Paul. From Paul’s Letters, we can gather that:
1. The man’s name was Paul: A Greek name.
2. He had a Jewish name, Saul. Remember, having two names was not uncommon for Jews who lived outside Palestine in the first century.
3. Paul was born in Tarsus, a city in Southwestern Asia Minor.
4. He came from a family of Pharisees of the tribe of Benjamin and was named for the tribe’s most illustrious member, King Saul.
5. Paul studied under the famous teacher Gamaliel (Acts 22: 3), the grandson of Hillel. Hillel is known as the Academy of Hillel, founded by a Jewish sage called Hillel the Elder. The House of Hillel was a school of Jewish law and thought that was very well known in the 1st century B.C.E. Jerusalem.
6. Since Paul’s letters show familiarity with rabbinic methods for interpretation of Scripture and popular Hellenistic philosophy to a degree, this makes it likely that he received a formal education in both areas. Hence, Paul’s exegesis of the Old Testament shows evidence of his rabbinic training.
7. Paul was probably, as an adult, a resident of Damascus. 
8. In many places, Paul discusses his Jewish identity. He says “ I am a Jew” (Acts 22;3) “I am a Pharisee” (Acts 23;6), and “I am a prisoner for the sake of the hope of Israel” (Acts 28:20).
Paul was an active persecutor of the early Christian movement:
The language Paul uses in his pre-revelatory encounter with the risen Lord shows how much how antagonistic he was towards the messianic movement. In Gal. 1:13-15, Paul uses terms such as “persecute” and “destroy” to describe his efforts to put an end to the spread of the early faith.
Even though Paul does not give a list of the reasons why he was an ardent persecutor of the early Messianic Movement, this reasons for being a persecutor was probably due to several reasons:
First, he may have perceived it to be a threat to Torah obedience. We need to keep in mind that in within the historical background of the first century, if a Jewish person was to deny the Torah as part of their practice, they would be denying the fact that they were a Jew! 
Second, given how he speaks about this topic in his letters (Gal 3:13;1), Paul was most likely aware of Deuteronomy 21:22-23: “If a person commits a sin punishable by death and is executed, and you hang the corpse on a tree, his body must not remain all night on the tree; instead you must make certain you bury him that same day, for the one who is left exposed on a tree is cursed by God. You must not defile your land which the Lord your God is giving you as an inheritance.” The context of this verse is describing the public display of the corpse of an executed criminal. To say that crucifixion was portrayed in a negative light within Judaism in the first century is an understatement. “Anyone hung on a tree is under God’s curse”-the very method of death brought a divine curse upon the crucified. In other words, anyone who was crucified was assumed not to be the Anointed One of God. So Paul most likely found the idea of group of Jewish people following a crucified Messiah to be abhorrent.
Third, given what we see in Acts 8 (following the stoning of Stephen in Acts 7) we see that Paul most likely found the Jesus movement as a threat to the Temple. It says in Acts 8: 1-3,
“Saul was in hearty agreement with putting him to death. And on that day a great persecution began against the church in Jerusalem, and they were all scattered throughout the regions of Judea and Samaria, except the apostles. Some devout men buried Stephen, and made loud lamentation over him.But Saul began ravaging the church, entering house after house, and dragging off men and women, he would put them in prison.”
What Can We Know About Paul’s Revelation of Jesus ?
Jesus was crucified about 33 A.D. According to many scholars, Paul became a follower of Jesus around 35 A.D. Remember, Paul’s letters are dated between AD 40 and 60.
Also, Paul did not follow Jesus from the beginning. However, Paul is still considered an apostle, though “abnormally born” and “the least of the apostles” (1 Corinthians 15:8-9). His turning to Jesus happened though a dramatic revelatory encounter (Acts 9: 1-7). His first years as a follower of Jesus in Arabia remain a mystery.
Three years later after his call, he went to Jerusalem to visit; this is where he saw Peter and James and most likely received the doctrinal content of the Gospel that he goes on to discuss in 1 Cor. 15:3-8. So in this case, we must differentiate between between essence and form. The essence of the gospel, that Jesus of Nazareth was truly the Son of God, was revealed to Paul on the life changing moment on the Damascus road. Paul realized that those that he had been persecuting had been right all along about Jesus being the Messiah. As far as the form the gospel, this includes the historical undergirding of certain events, certain phraseology used to express the new truth and doubtless many other things that were passed onto Paul by those other than him. 
As already mentioned, in many places, Paul discusses his Jewish identity. He says “ I am a Jew” (Acts 22;3) “I am a Pharisee” (Acts 23;6), and “I am a prisoner for the sake of the hope of Israel” (Acts 28:20). Notice that Paul didn’t say “I was a Pharisee” or that “I was a Jew.” So perhaps it is inaccurate to say that Paul switched religions. Hence, it would be more reasonable to say that while Paul did have a radical reorientation about his theology, but he more likely received a “call” rather than a conversion to a new religion. If anything, Paul did ‘repent.’ The Hebrew word for repent is “shub” which means to “turn back” or “return.” So Paul was most certainly restored to the God of Israel through the Messiah. But the old saying, “Paul converted to Christianity” has not gone unchallenged within New Testament scholarship.
What does the Resurrection of Jesus explain in relation to Paul’s coming to faith in the Messiah?
#1 The Resurrection of Jesus explains the appearance to Paul was not a vision:
If Paul did have a vision then the term “vision” is vague and must be defined. As Licona points out, visions are either objective (i.e., something that is seen without the use of our natural senses) or subjective (i.e., a product of our minds). The real problem is with the vision hypothesis is that it doesn’t explain Paul’s use of resurrection to explain what had happened to Jesus. The two words are used for resurrection in the New Testament are “anastasis” (rising up) and “egersis” (waking up), which both imply a physical body. Furthermore, the use of the word “opethe” (the Greek word for appeared) shows the Gospel writers did believe that Jesus appeared physically.
“There you will see (opethe) him” (Matt. 28:7); “The Lord has risen and has appeared (opethe) to Simon” (Luke 24:24). When they used “opethe” here, it means that He appeared physically to them. So when Paul gives his list of appearances in 1 Cor. 15, the issues becomes whether the appearance to him is the same as it was to the disciples. There is no doubt the post resurrection body of Jesus (after the ascension) had to be somewhat different than the body the disciples saw. Also, whenever the New Testament mentions the word body, in the context of referring to an individual human being, the Greek word “soma” always refers to a literal, physical body.Greek specialist Robert Gundry says “the consistent and exclusive use of soma for the physical body in anthropological contexts resists dematerialization of the resurrection, whether by idealism or by existentialism.”  Furthermore, in N.T. Wright’s The Resurrection of the Son of God shows that the Greek word for resurrection which is “anastasis” was used by ancient Jews, pagans, and Christians as bodily in nature.
The Resurrection helps explains Paul’s Christology
As already mentioned, Paul’s Letters are the earliest records we have for the life of Jesus. They are also the earliest letters we have for the Christology of Jesus. In several of Paul’s Letters Jesus is referred to as “Lord” (Gr. kyrios). Hence, the willingness to do this place Jesus in a role attributed to God in Jewish expectation.” For a Jewish person, when the title “Lord” (Heb. Adonai) was used in place of the divine name YHWH, this was the highest designation a Jewish person could use for deity.
Also, as pointed out by Richard Bauckham in his work on this topic, Paul believed that Jesus was God by attributing attributes to him that were distinctly reserved for God. And he did so in a distinctly Jewish manner while also preserving monotheism. There were three attributes that first century Jews uniquely assigned to God:
1. God is the Sole Ruler of all things
2. God is the Sole Creator of all things
3. God is the only being deserving of worship
So let’s look at how Paul matches up the data here:
1. Jesus participates in God’s sole rule over all things
Phil: 3:20-21: “For our citizenship is in heaven, from which also we eagerly wait for a Savior, the Lord Jesus Christ; who will transform the body of our humble state into conformity with the body of His glory, by the exertion of the power that He has even to subject all things to Himself.”
Eph. 1:21-22: Paul speaks of Jesus being “far above all rule and authority and power and dominion, and every name that is named, not only in this age but also in the one to come. And He put all things in subjection under His feet…”
Here, Jesus is clearly given the authority to rule above every one of God’s created beings.
2. Jesus as the Creator of all things
Jesus is clearly thought by Paul to have been the creator of the universe. This attribute is reserved only to God in Second Temple Judaism. Paul makes it clear that Jesus created all things.
Col. 1:15-16: “He is the image of the invisible God, the firstborn over all creation. For by him all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities; all things were created by him and for him.”
3. Jesus as worthy of worship
As discussed above, only God was worthy of worship in Second Temple Judaism. Nevertheless, Paul discusses the worship of Jesus. Since God is the sole Creator and Ruler of all things He alone should be worshiped. Even within the Roman Empire, Jews worshiped God alone. No other entity was worthy of worship. Here is one of the earliest Christological texts:
Philippians 2:6-11: “Who, being in very nature God, did not consider equality with God something to be grasped, but made himself nothing, taking the very nature of a servant, being made in human likeness. And being found in appearance as a man, he humbled himself and became obedient to death even death on a cross! Therefore God exalted him to the highest place and gave him the name that is above every name, that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father.”
In the end, it is clear that Paul had a dramatic change that turned him from a persecutor of the early followers of Jesus to the greatest missionary of the early faith. Someone may object and say it is not a big deal for someone to make such a radical change in their beliefs in antiquity. After all, people change beliefs all the time (i.e. people leave Islam for the Christian faith or vice versa). In response, I suggest doing a thorough study of the honor and shame culture that Paul was acquainted with. You will see it was much more of a challenge to change one’s beliefs in antiquity than it is today. I submit that the bodily resurrection of Jesus is the best explanation for the change in Paul’s life.
 Michael R. Licona, The Resurrection of Jesus: A New Historiographal Approach (Downers Grove, ILL: Intervarsity Press, 2010).
 Bart Ehrman, The New Testament: A Historical Introduction to the Early Christian Writings. Third Edition (New York, Oxford: Oxford University Press, 2004), 276.
 Dale Allison, Resurrecting Jesus: The Earliest Christian Tradition and Its Interpreters (New York: T&T Clark, 2005), 263-268.
 Most of points 1-8 are laid out in Marion Soard’s The Apostle Paul: An Introduction to his Writings and Teaching (Mahwah, New Jersey: Paulist Press, 1987), 10-11.
 See Martin Hengel’s The Pre-Christian Paul (Philadelphia: Trinity Press International, 1991).
 D. A. Carson, D. J. Moo, and Leon Morris, An Introduction To The New Testament(Grand Rapids: Zondervan Publising House, 2002),220.
 Norman Geisler. Baker Encyclopedia of Christian Apologetics. (Grand Rapids, MI: Baker Books 1999), 668.