Martin Luther was a theologian and monk famous for his public denunciation of the Catholic Church, particularly its practice of selling indulgences, or forgiveness for minor sins. After he was excommunicated, he preached against the corruption of the church and created a schism in the Christian world. Luther's actions spearheaded the Protestant Reformation, creating a new branch of the Christian religion that renounced the bureaucracy of the central church and focused solely on the Bible for guidance.
After becoming a monk, Martin Luther began to see the Catholic Church as corrupt and too concerned with worldly matters such as wealth to properly guide the flock to heaven. In particular, he despised the practice of selling indulgences. If a member of the flock committed a minor sin, he could simply pay the church for forgiveness rather than perform acts of contrition. Luther wrote a letter condemning the practice in 1517 and asked the Archbishop of Mainz to discontinue selling indulgences. When officials of the church challenged Luther on his statements, Luther publicly defied them, stating that the only authority he answered to was the Bible itself.
Another of Martin Luther's key beliefs was that common people should be able to read the word of God for themselves instead of relying on a scholar to interpret it for them. To this end, he translated the Bible from Hebrew and ancient Greek into German, allowing believers to read the text for themselves for the first time.