2017 marks the 500th anniversary of the Protestant Reformation.

Why 2017? Because on October 31, 1517 a 34-year old Augustinian monk named Martin Luther reportedly nailed “95 theses”—a standard tool for academic discourse in the university system at the time—to the Castle Church door in Wittenberg, Germany. While the presentation of the theses is relatively innocuous, the substance of the theses became a spark that would change the face of Western Christendom forever.

In this anniversary year, there has already been much said about Luther, and it seems like there is much more still. However, it’s important to stop and ask ourselves: why does Luther matter? Is there something that we can point to that he brings uniquely to those who call themselves Christians?

Luther matters—and at least for two reasons.

1. His emphasis upon the Word of God as the supreme rule for the Christian life.

Key to Luther’s Reformation project was a return to Scripture as the supreme rule for the Christian life. In late-medieval Europe, Christian worship and theological discourse became increasingly distanced from the page of Scripture. While it’s not that Scripture wasn’t important to the theologians of the Middle Ages, it is true that theological discourse began to focus around questions of philosophical distinctions over subtle matters.

A central emphasis in Luther’s theology is a recovery of the Word of God in the life of the Christian community. For Luther, the Word of God and it’s meaning is clear. It’s not only for the curia or religious leaders, but for all Christians.

This understanding of the Word of God would also lead Luther to translate the New Testament from Greek to German while he was in hiding from the Roman Catholic magisterium in 1521. The “Luther Bible” would go on to shape German, Christian practice, and Western culture forever.

2. His recovery of the doctrine of justification by faith alone.

This emphasis has two corollaries: on the one hand, Luther’s doctrine of justification doesn’t make sense apart from his understanding of sin. For Luther, all works—even works that look good externally—are fundamentally tainted by sin. What this means is that the individual who stands before God has no righteousness of his own.

This why justification by faith alone is so important: through faith, the individual is given the righteousness of Christ so that his confidence before God is a righteousness outside of him—what is called, theologically speaking, “alien righteousness.” This recovery of God’s grace came through a reading of Paul’s letter to the Romans in particular. This insight from Luther would remain a lodestone for the Reformation through his immediate heirs all the way until today.