Having described the experience of Jewish Christians as coming into their full inheritance, Paul described the conversion of Gentiles (non-Jews) in Galatians 4:8-20.  Simply speaking, they (we) had not known God but then came to know him.  However, the Galatians later turned back to a form of religion that was similar to what they had when they were enslaved to idols.  Therefore, they serve as a constant reminder to all of us not to revert to a religion of law-keeping but to continue to trust in Christ alone.