Here's a quote from Tim Keller's new book, Galatians For You . I'm halfway through, and a review will be forthcoming next week, God willing. Peter's sin was basically the sin of nationalism. He insisted that Christians can't be really pleasing to God unless they become Jewish. But nationalism is just one form of legalism. Legalism is looking to something besides Jesus Christ in order to be acceptable and clean before God. Legalism always results in pride and fear, psychologically, and exclusion and strife, socially... One way is to be sectarian. Every Christian group or denomination necessarily has many distinctions of belief and practices that have less to do with the core gospel beliefs and more to do with specific convictions about ethical behavior or church policy. It is extremely easy to stress our distinctions in order to demonstrate to ourselves and others that our church is the superior or best one. Another way is to bring class-ist, nationalistic, o...