Last week in Galatians 1:1-10 Paul opens the letter with his usual introduction, skips his usual commendation and jumps right into the problem. The churches in Galatia were in the process of adding to the gospel he has preached to them. They were adding works to the act of salvation by grace.
In the rest of chapter one and the first part of chapter two Paul strengthen’s his own apostolic authority:
1:11-24 - Paul explains that he was commissioned an apostle by Christ Himself, referencing his Damascus Road experience.
2:1-10 - Paul relates his trip to Jerusalem where the original apostles affirm him as an apostle to the Gentiles. They see how God is working through Paul and give him their full support. Many believe this was the same meeting known as the Jerusalem council.
Now Paul turns his focus on the root of the problem - Justification by faith alone