A Christian missionary who once persecuted the church More lays out the fundamental argument of his letter: there is only one Gospel and it comes from Jesus is the Messiah whose life, death, and resurrection are God's saving act for humanity More Christ himself.
Unlike many of his other letters (Romans 1:8; 1 Corinthians 1:4, 1 Thessalonians 1:2, Philippians 1:3), Paul does not begin his letter to the Galatians by giving thanks to God for them. Rather, he launches straight into his bewilderment at how quickly they have deserted him (1:6). He expresses his dismay at the Galatians’ behavior with the strongest language available to him, the language of ancient curses. Twice in a row, he curses those who preach “contrary gospels” with the phrase “Let him be accursed” (1:8, 1:9). Though such language may sound old-fashioned to a modern ear, within the context of the ancient world, the fear of curses and their ability to harm was constant. By employing curses in his opening argument, Paul seeks not just to restrain his enemies, but also to impress upon his audience the seriousness of their desertion from the Gospel.
The curses set up a pair of contrasts that Paul uses to illustrate how to evaluate a gospel. In his first contrast, between human approval and God’s approval, he argues that only those who seek God’s approval are servants of Christ (1:10). In his second contrast, between a human source and revelation, he argues that only a revelation of Jesus Christ can establish the truth of the Gospel (1:11). Paul sharpens the contrast between human and divine sources by including “angels from heaven” under his curse, in essence, claiming that angels are no better than humans as sources of the gospel. For Paul, it is Jesus Christ or nothing. In both contrasts, Paul seeks to differentiate himself from the others who preach to the Galatians and to give his audience criteria for judging the messengers that visit them.
The severity of Paul’s language and the sharpness of his contrasts highlight his central concern. Paul wants the Galatians to understand, without any doubts, that the Gospel that he preaches is the only Gospel because it comes directly from Jesus Christ (1:12). Therefore, they must accept no imitations, substitutes, or modifications.