Why is grace alone essential for salvation?

Grace alone is foundational to the gospel as it emphasizes that salvation is a gift from God, not something we can earn through our deeds. Ephesians 2:8-9 states that we are saved by grace through faith, and this not of ourselves; it is the gift of God. This means that our salvation is entirely dependent on God's mercy and love, undermining any attempt to rely on personal merit or works, which would frustrate the grace of God, making it secondary instead of primary in the process of redemption.