The Protestant Reformation Many ideas of the Renaissance like humanism, individualism and secularism stimulated a strong critique of the church's policy and the clergy's behaviour. Many people regarded it as a scandal that the catholic church sold indulgences. Indulgences were documents, stamped by the church which could reduce your sins. People who bought indulgences believed that this document could pave their way to heaven. In northern Germany they went so far that they even sold indulgences which could reduce the sins which you are going to commit in the future. They also sold indulgences for the salvation of somebody's dead relatives.
Martin Luther a German priest, who lived in the small city of Wittenberg was the the most famous critic of the corrupt practices of the Catholic church. He wrote his critiques down in 95 theses on a door of a church in Wittenberg. These 95 theses spread quickly all over Germany and parts of northern Europe. The first reaction of the catholic church was a reduction of the sales of indulgences. But this sale was not the only point Luther criticized in the Catholic church. The Catholic church taught that salvation comes from faith, good deeds and the assistance of the church.
Martin Luther's concept was that salvation comes by faith alone. Martin Luther also translated the bible into German. So far the bible was only written in Latin and the most people could not read it. For Protestant people the bible was the only source of truth.
After a long argument between Luther and the church Luther was excommunicated from the church in the year 1521. That meant that he was not allowed to be a catholic priest anymore. After that he founded a completely new form of christianity - protestantism. A century later so many people were convinced by Luther's new ideas of Christian religion that they founded new forms of Protestantism like Calvinism, Anabaptism and the Church of England.