1) Paul uses 6 arguments in Galatians 3-4 to prove that salvation is by grace alone, not works. The personal argument references their experience receiving the Holy Spirit when first believing. 2) Paul questions why they would abandon the Spirit if they began in the Spirit. He references scripture like Genesis 15:6 to show Abraham was justified by faith, not works. 3) Paul argues salvation is for Gentiles too, based on God's promise to Abraham in Genesis 12:3. He cites Habakkuk 2:4 to prove salvation is by faith, not works as outlined in the Law.