At the beginning of the letter to the Galatians, Paul must clarify his relationship with the Jerusalem church. Polhill wonders why Paul thought he had to spend so much effort at the beginning of this letter to prove his independence of his Apostolic office (Paul and his Letters, 146). The usual answer, he comments, is that his opponents, the Judaizers, are attacking him as an illegitimate apostle, forcing him to defend his calling.
There is another possibility for this autobiographical section, according to Polhill. He may be offering his life as a model for the Galatians. Paul was converted to a gospel of freedom on the road to Damascus, just as the Galatians were when Paul preached that gospel to them. Just as Paul did not go back to Jerusalem and place himself under the authority of the old order, now the Galatians ought to resist “returning to Jerusalem” by keeping the Law.
The bottom line is that if Paul is under the authority of Jerusalem, then it is at least possible that the “men from James” could claim that Paul has not been authorized to preach a gospel to the Gentiles which frees them from the Law. These Judaizers may have styled themselves as the real followers of Jesus and Paul as the aberration. Paul therefore stresses that his calling is from the resurrected Jesus himself and that his gospel came directly from the Lord.
At issue here is not the Gospel that Christ died for our sins, was buried, and that he was raised on the third day, according to the scriptures (1 Cor 15:3-5). Paul clearly states that this gospel was passed along to him as the primary core of the gospel. It is also clear that the preaching of Christ Crucified can be found in the apostolic preaching form the beginning. What Paul is going to argue in the next two chapters is that his Gospel is Christ Crucified, but when the death and resurrection of Christ is applied to the gentiles, they are not under the Law. They are not converts to Judaism by rather adopted children of God and therefore free from the law.
Paul is therefore adamant that Gentiles who try to keep the Law are not really followers of Jesus, but rather Gentiles who are converting to Judaism. What sort of ethical and social ramifications will this “freedom in Christ” have on his churches? That is the point of the last third of the letter.