If by “founding” is meant the creation of a movement single-handedly, Paul did not found Christianity. Christianity as we know it is fundamentally an invention of the Fourth Century. Until its concretization under Constantine and subsequent emperors, Christianity was a collection of varied movements deriving their basis in Jesus’ person, mission, and teaching and the “kerygma” or early preaching of those claiming historical roots in Jesus himself. These groups received their respective Jesus-data from cherished teachers (and sometimes, they claimed, directly from the Holy Spirit). That is to say, Christianity was not so much founded as it evolved. Paul was only one – though an important one – of its midwives.
Without doubt Paul founded communities based on his vision of the gospel, and his authentic letters give a sense of his desparate struggle to keep them in conformity with his teachings. Yet Paul mentions many other teachers, some of whom are helpful, others who are inimical, to Paul. Paul’s missionary activity did not take place in a vacuum, and he was just one, not the only, “founding father” in early Christianity.
Paul’s primary nemesis paradoxically was the original group of Jesus’ followers who were operating out of Jerusalem after the crucifixion. Having known Jesus during his lifetime and experienced him as “risen” in their native Palestine, they occupied the pinnacle of dissemination of information about Jesus. It was these, Jesus’ Jewish disciples, with whom Paul had the most intense conflict.
From Paul’s own letters it would seem that the primary issue of contention with Jerusalem concerned the Jewish Law and its observance. His christology – with its vision of Jesus as the self-emptying heavenly Adam-Christ, raised to the judgment seat at God’s side – seems entirely Jewish, if sectarian. Not so Paul’s attitude toward the Law.
Jesus and his Judean disciples were in all likelihood observant of Torah, at least within their sectarian definitions of Torah, and within Jesus’ personal Torah-interpretation. In one form or another, they were “zealous” for the Law. But, like their mainstream Jewish confreres, they were not unreasonable in their application of it to converts. For both mainstream Judaism and the sectarian Jesus movement, Gentile proselytes need only practice the so-called “Noachide” laws in order to join the Israelite community. Jews, of course, would always continue to be Torah-observant.
Acts 15:1-33 details, from author Luke’s point of view, how the Jerusalem disciples under James (Jesus’ brother) permitted Gentiles to enter the Jewish Jesus movement without becoming Torah-observant Jews. As with the macrocosm of standard Jewish practice, in James’s group, Gentiles would enter as “Noachides” while Jews would remain Torah-observant. Paul broke with this provision to which (Luke says) he had given his whole-hearted agreement.
Luke (Acts 21: 17-26) says that the Jerusalem disciples had heard rumors that Paul had been telling his Gentile congregations that Torah, by virtue of Jesus’ grace, was no longer valid, even for Jews. This of course flew in the face of James’ decision in Acts 13. Paul in his own letters attests that this was indeed the case: Torah is defunct (Romans 3:20, 28; Galatians 3:13, 10, 24-25) for both Gentiles and Jews (including native Jewish followers of Jesus).
Christianity was not founded by Paul, but Pauline theology turned out to be a particularly apt vehicle for Gentile Christianity: not only were Gentiles excused from Law observance (thanks to the Noachide rule), but now since (according to Paul) Torah was a dessicated shell, it was irrelevant to salvation. Gentiles need not trouble themselves over it, especially in view of the fact (thanks to Paul) it was no longer valid even for its progenitors and heirs, the Jews. Thus a “lawless” New Covenant was ripe for selecting and application.
The selector was the monarchical episcopacy, the network of bishops whose authority and efficient communication systems adopted, shaped, and ultimately enshrined Paulinism as its own. From now on, Christianity would be a form of Paulinism admixed with Johannine theology and Greek philosophy. Paulinism would be received along with the primary Christian catechesis. The original doctrines of James and Jesus’ first Jewish disciples would be relegated to marginal groups such as the Ebionites, Nazoreans, Elchaisites and others.
The adoption of Paul’s thinking and its general application to the church was the foundational moment, or rather the series of such moments – unfolding over decades – that coalesced the Christianity we are familiar with.