Martin Luther’s key essay "Concerning Christian Liberty, " written in 1520, summarizes the heart of the Protestant Reformation and lays out Luther’s profound theological insights. Luther addresses the Christian’s relationship with faith, freedom, and good acts in this brief treatise. Luther’s key claim is at the heart of the book: real Christian freedom is the fruit of faith in Christ. He claims that faith justifies the believer and frees them from the shackles of sin and the law. Luther’s argument is based on the concept that salvation is a gift from God, acquired alone via faith, and cannot be won through good works or human merit. Luther’s work also highlights the "dual nature of the Christian" – that a believer is both a free ruler overall and a faithful servant to all. He encourages Christians to live out their religion by loving their neighbors rather than attempting to gain salvation by external acts of devotion. "Concerning Christian Liberty" is an in-depth examination of the relationship between faith, freedom, and good acts. Luther’s views transformed Christian teaching by emphasizing the centrality of trust in Christ and the transformative power of grace.