How do we know that grace alone is sufficient for salvation?

The doctrine of grace alone underscores that salvation is an act of God entirely dependent on His grace rather than on human effort. Ephesians 2:8-9 affirms that it is by grace we are saved, through faith, and this is not of ourselves; it is a gift of God, not of works, lest anyone should boast. This reinforcement of grace emphasizes that salvation is a manifestation of God's sovereign will, devoid of merit on our part, revealing the depths of His love for humanity as He seeks those who are dead in trespasses and sins to reveal Christ to them.