Protestant Christians affirm salvation by grace, that a person is saved not by their own merit or works but by God's unmerited favor, received through faith. The classic statement is Paul's: by grace you have been saved through faith, and this is not your own doing, it is the gift of God, not a result of works (Ephesians 2:8-9). Recovered as a rallying principle of the Reformation in the formula sola gratia, grace alone, the teaching is closely tied to Martin Luther's own theological breakthrough, a crisis of conscience over how a sinner could stand righteous before God that he resolved through his reading of Paul's letter to the Romans, and which propelled the wider Reformation critique of a medieval penitential system he judged to have made grace something earned through the church's own mechanisms rather than freely given.
Within Protestantism itself, the doctrine generated a further, sharp internal debate over exactly how grace relates to human freedom. Reformed and Calvinist theology holds grace to be effectual and, for the elect, ultimately irresistible, God's choice determining salvation from eternity; Arminian and Wesleyan theology, associated with Methodism, holds instead that grace, while entirely God's initiative, can genuinely be resisted or accepted, preserving a real, if grace-enabled, human freedom to respond. Both sides affirm sola gratia while disagreeing sharply over what that grace actually does to the human will.