October 31st marks the day Martin Luther, who was an Augustinian monk at the time, nailed his 95 theses on the chapel doors of the Wittenberg Castle in Germany, in 1517. His theses contained criticism on errors he found in the Catholic Church and suggested reforms.  He particularly criticised the Church for selling indulgences and accused the Church of using the money to build Saint Peter’s Basilica. Luther’s theses were rejected by the Church and his refusal to abandon them led to his excommunication a few years later. But his ideas spread throughout all of Europe. Were therefore called “protestant” all those who contested, with Luther, the Catholic Church. Then came the Counter-Reform, marked by the Council of Trent, still in the 16th century, and it was the first attempt to push back against Protestantism. And this war of religions inevitably led to the Thirty Year War at the beginning of the 17th century. Today, the ideas of Martin Luther remain, though they have opened up other branches of Protestantism. Apart from the sale of indulgences – indulgences still exist today but do not come with a fee, rather they are an invitation to personal conversion – Luther insisted on the authority of Scripture and the individual interpretation of the believer. This meant giving people access to the Bible and teaching them how to read. Other differences arise when it comes to the belief of Mary’s virginity, the veneration of the saints, and the principle of justification. On this last point, Lutherans and Catholics have found common ground. Salvation is found through grace, and aided by works. They came to this agreement in 1999 when they signed a joint declaration titled from Conflict to Communion. On the Eucharist. Catholics believe in the real presence of Jesus in the bread and wine. For Protestants, it is a symbol. They also don’t agree on the status of priests and ministers as well as on the authority of the Pope and the magisterium. There are 800 million Protestants in the world today and about 1.2 billion Catholics. In Sweden, where the Pope spent 2 days, the number of Protestants represent a little more than 60% of the population.   Check out Emilie Callan's summary of Protestant history on Vatican Connections: