How do we know Paul is not a liar?
Paul is not a liar because his message that the righteousness of God apart from the law is manifested, as attested by the Law and Prophets, is true. He laid the foundation as a wise master builder by God's grace. If his writings were false, he would be the biggest liar and imposter, but he is not.
Les explains that the truthfulness of Paul's message is confirmed by the fact that the righteousness of God without the law is manifested and witnessed by the Old Testament Law and Prophets. He stresses that if Paul's writings were not true, Paul would have the hottest corner in the lake of fire and be the biggest liar and imposter who ever wrote, but he is not. Les points to 1 Corinthians 3:9-10, where Paul says he laid the foundation as a wise master builder according to the grace of God given to him, and if he did not lay that foundation, then he would be a liar. Thus, Paul's apostolic claim and gospel are validated.