The threat to this unity is dramatically displayed here as the scene shifts from Jerusalem, the center of the Jewish identity, to Antioch, a Gentile city where followers of Jesus were first called Christians.  Paul demonstrates what he wrote earlier, that he doesn’t view Peter and other apostles from Jerusalem as his superior.  Paul confronts Peter for betraying the very gospel that they had agreed upon in verses 1-10.  Peter’s behavior denies the power and implications of Christ’s death, undermining that followers of Jesus are justified by faith, not ‘works of the law’.  Themes like nationalism and racism can be teased out in this sermon, showing that they flow from the same root – legalism. (See TK, 196)