Final answer:
Martin Luther was a German monk whose actions began the Protestant Reformation, particularly with his 95 Theses in 1517. He advocated for Christian practices and scripture to be in the vernacular, differing from the Catholic Church, and his ideas spread quickly due to the printing press.
Step-by-step explanation:
Martin Luther was a seminal figure in the Protestant Reformation, sparking a religious movement that transformed Christianity in Europe. He was an Augustinian monk and professor of theology at the University of Wittenberg. In 1517, he famously nailed his 95 Theses to the door of the Castle Church in Wittenberg, challenging the Catholic Church's sale of indulgences and other practices. His bold actions and prolific writing, enabled by the invention of the printing press, allowed his ideas to spread widely. Luther was eventually excommunicated but continued to write and translate the Bible into German, advocating for worship and scripture reading in the vernacular.
Luther's influence extended beyond religion to the culture and politics of the day. He was friends with the German painter Lucas Cranach the Elder, who painted several portraits of him. Despite originally seeking to reform the Catholic Church, Luther's efforts resulted in a schism, forming what is known today as Lutheranism. He preached that salvation was through faith alone and emphasized the authority of scripture over the teachings of the Church—a stark contrast to the Catholic doctrine of the time. His reformist ideas paved the way for other branches of Protestantism and significantly altered the course of religious history in Europe.