A.B. Simpson emphasizes the dependability of God as highlighted in 2 Corinthians 1:20-22, where all of God's promises are affirmed in Christ. He addresses the criticism faced by the Apostle Paul regarding his trustworthiness, explaining that God's character is unwavering and His promises are fulfilled, regardless of human circumstances. Simpson illustrates that God's promises are varied, sure, and reassuring, and that His grace is stable and transformative in the lives of believers. He encourages the congregation to trust in God's faithfulness and to respond with 'Amen' to His promises, thereby glorifying God through their faith. Ultimately, the sermon calls for a deep reliance on God's dependability as the foundation of a believer's life.