For many decades (maybe even for hundreds of years) Paul, who considered himself an apostle, was routinely described as a man who had “converted” to Christianity from Judaism. Virtually all of the people who described Paul in this manner are/were themselves Christians, perhaps a few agnostics/atheists—even some Jews. Scholars of how Christianity arose seemed to be primarily interested in separating Christians from Jews, although they often acknowledged that the roots of Christianity were in Judaism. In fact, The Christian “Bible” includes all of the books of the “Old Testament” with some variations between and within the Orthodox, Roman Catholic and various Protestant versions. The early Christian theologian, Marcion, wanted to omit all of the Old Testament, but he was an outlier.
In the usual versions of Paul’s history, his enemies were/are almost uniformly described as the Jews, especially the clergy (Temple priests) and later the rabbis, although the Jerusalem Temple was still in existence during Paul’s life. He lived from approximately 5 C.E. to 67 C.E., and the Temple was destroyed by the Romans in 70 C.E.
While the issue is still debated, and probably most Christians think of Paul as himself a Christian, and the Jews as his opponents, leading scholars now assert that Paul never converted, and remained a Jew for his entire life. These scholars also believe that in Paul’s theology, the enemy was not “the Jews,” but the Roman empire.
Paul describes himself as an apostle, chosen not by any man, but directly by God, as represented by His only Son, Jesus Christ. He further asserts that he is God’s apostle to the “Nations.” This word is often translated as “Gentiles,” which many take to mean as “Christians.” However, this is a rather careless analysis. In Jewish Scripture, God tells the Israelites he has chosen them as a nation of priests, a holy nation, and they are instructed to minister to the rest of the (known) world—the nations--and bring them to God.
It is unclear whether Paul intended to bring the “Nations” directly into Israel’s covenant with God, which I believe is the correct interpretation. There are scholars (Bernard Brandon Scott) who believe there was to be a second covenant between the Nations and God, but since all of humanity is to eventually share in God’s universal kingdom, I think this is an unnecessary complication.
On the other hand, Paul believed the nations were to be exempted from some of the commandments and rules that were the obligations of the Jews. For example, circumcision was not required, nor were most of the dietary restrictions. Modern commentators often describe these rules—the 613 “commandments” as burdensome, although objective scholars in the modern era acknowledge that the Jews of Jesus’s time did not find them onerous and were pleased to have detailed instructions of how to please God. Nevertheless,
Nevertheless, it was and remains much easier to fulfill the requirements set by Paul than the more stringent standards for conversion to Judaism.
There was another major element of Paul’s teaching. The idea of apocalypticism—the world was going to end very soon and God’s judgment was about to be rendered. Those who accepted Jesus as their Lord would indeed be saved. Those who did not were doomed to eternal torment. Paul told his adherents the apocalypse was imminent--thus conversion was not only easy, it was a matter of life or death. If Paul didn’t invent Christianity, he was its greatest booster. I wonder what Jesus would think...2 billion plus converts to a religion he wouldn’t recognize.