Paul wrote a letter to the Galatians to address those who were teaching a different gospel and deceiving Christians. In the introduction, Paul establishes the divine inspiration and authority of his letters. He then summarizes the true gospel as Jesus giving himself for sins so people could be freed from this evil age. Paul expresses astonishment that the Galatians have deserted the true gospel for a false one. He asserts that he preaches the gospel from revelation, not to please men or according to man, but according to God.