We see from Paul’s opening line in Galatians 1:1 that his authority as an Apostle sent by God was being questioned. From the very beginning Paul seems to emphasize that his authority came not from men but from God. Therefore, the men from James must have sought to undermine Paul’s position as a legitimate Apostle of Christ, before they could have hoped that the Galatians would listen to their doctrine, which removed its adherents from the grace found in Christ (Galatians 1:6). Apparently these men began by saying Paul was a man-pleaser. That is, he sought to please the gentiles of Galatia by not requiring them to be circumcised (Galatians 1:10), which these men taught was necessary for salvation (Acts 15:1).
Once Paul’s authority was called into question, these men could put themselves into that position of supreme authority. They could then begin to contradict Paul’s words as doubt was sowed in the hearts and minds of the Galatian believers. Much later in his life, Paul would tell the Jews at Jerusalem (Acts 22:1-3), that he was a Jew from Tarsus in Cilicia who as a young boy was brought up at the feet of Gamaliel, the well respected rabbi of the 1st century CE. The agitators who had come to the Galatian churches were saying that Paul learned the Gospel at the feet of the Apostles—the Twelve, who had learned it at the feet of Jesus. This is what Paul is responding to in this part of his letter. The argument was: just as the Apostles couldn’t deviate from what Jesus had taught them, neither could Paul deviate from what the Twelve taught him. The agitators taught that Paul was obligated to preach the very same message the Apostles in Jerusalem preached to Jews. Therefore, just as the Jews in Jerusalem were obligated to obey the Law of Moses, so were the gentiles wherever they lived.
Consequently, this is the first question that Paul had to address. From where or from whom did he receive his authority and his Gospel? He claimed it wasn’t a philosophy he learned from men, nor was he taught it, nor was he commissioned by the Twelve to preach it (Galatians 1:11-12). Rather, he received it from God by revelation. Paul confessed that years earlier he had persecuted believers and sought to destroy the Church of Christ, and, in doing so, he showed he was more zealous for Jewish traditions than many other young Jewish men, and he excelled above them in his faith (Galatians 1:13-14). Nevertheless, Jesus appeared to Paul in glorious form while he (Paul) was traveling to Damascus (Acts 9:1-9; Acts 22:6-11; 26:12-21).
Paul knew Jesus was crucified and believed he had been cursed of God (Deuteronomy 21:23). Nevertheless, it was Jesus who appeared to him near Damascus. Therefore, although Jesus was crucified by men, God declared him innocent by resurrecting him from the dead. This was Paul’s Gospel according to what he told Agrippa in Acts 26:16, 19. He was empowered, according to Acts 26:18 to open the eyes of both Jew and gentile (cp. Acts 26:17) and turn them from darkness to light and from the power of Satan to the power of God. That is, Paul was to remove them from the power of the world and bring them into the Kingdom (or power) of God. In other words, Jesus is Lord or Messiah. This, and only this, was Paul’s Gospel. Anything added to this was unnecessary and unauthorized by God.
Why would Paul need to consult with the Apostles in order to understand that Jesus was resurrected or that he was the Messiah? The fact that Jesus appeared to Paul in a glorified state was enough to understand the core of the Apostles’ message at Jerusalem. This was Paul’s main argument against his accusers that he was commissioned by the Apostles to preach the Gospel of Christ. While the record of what Jesus said and did were useful in other ways, Paul simply didn’t need the records of Jesus’ ministry in order to preach his message that Jesus was alive and the Messiah.