How do we know that the gospel proclaimed by Paul came from God?
Paul is confident of the authority of the revelation he received. He is equally confident of his authority as an apostle.
After the opening declaration (Galatians 1:11-12), Paul goes on to talk of two things. Firstly, his Damascus Road experience-to show that his conversion and knowledge of the gospel have indeed come directly and personally from Jesus. Given his background as a persecutor of the church (v. 13) and his religious upbringing (v. 14), Paul would never have come to Jesus on his own. Something must have happened. Acts 9 gives a detailed description of how Saul the fearsome persecutor became Paul the passionate missionary. The once-enemy of the church makes it clear (Galatians 1:15-16) that what drastically turned him around was God's decision to firstly reveal Jesus to him, and then to appoint him to preach Jesus to the Gentiles-God's purpose for Paul from the time of his birth. He did nothing to earn God's call; in fact, he did the very opposite, but God acted out of grace. Secondly, since his conversion and calling were divinely initiated, Paul did not feel the need to turn to any human authority for verification-including the apostles in Jerusalem. Instead, he left for Arabia (v. 17) and avoided any human influence (v. 16). He was probably seeking the Holy Spirit's direct guidance to re-examine the same Scriptures that he, a highly trained Pharisee, would have already known so well. But now, with the Holy Spirit's help, his eyes would have been opened to see how all of the Old Testament had in fact been pointing to Jesus as Messiah and that everyone, Jew or Gentile, is saved by faith in Him alone. Being sent personally by Christ to reach out to the Gentiles (v. 16), he needed to make a careful study so that he could explain God's gospel-free of human influence-to people with little or no background knowledge of Scripture.
Paul is confident of the authority of the revelation he received. He is equally confident of his authority as an apostle. Both have divine origin. So, after examining the Scriptures for himself, he returned to Damascus (v. 17), feeling no necessity to check in with the other apostles in Jerusalem before preaching the gospel there.
Paul's teachings are experiential as well as knowledge-based. They are not careless human fabrications, but are founded solidly on Scripture and the direct revelation of God.
Isn't it amazing to discover that here is someone who used to keep the law zealously (v. 14)-and persecuted Christians-but is now preaching grace, not law? Paul is a living demonstration of salvation by grace, not works of the law. It shows God's forgiveness and not His condemnation. And this is the gospel we are sharing!