The Reformation

A Church under criticism

By the early 1500s, the Roman Catholic Church was the central institution of western European life, but many people voiced complaints about its practices. A frequent target was the sale of indulgences. In Catholic teaching, an indulgence reduced the temporal punishment a soul would face in purgatory before reaching heaven; by the sixteenth century, indulgences were sometimes sold, and the money funded church projects such as the rebuilding of St. Peter's Basilica in Rome. Critics argued that selling forgiveness confused spiritual grace with a financial transaction.

Calls for reform were not new, and they were not only about theology. Some rulers resented the wealth and political power of the Church and the flow of money to Rome. Humanist scholars of the Renaissance, studying the Bible and early Christian writings in their original languages, questioned later practices they could not find in scripture. Ordinary people and clergy alike criticized corruption, absentee bishops, and poorly educated priests. These grievances had circulated for generations without breaking the Church apart. What made the sixteenth century different was the combination of a compelling reformer, receptive rulers, and a new technology that could carry arguments to a wide audience faster than the Church could respond.

Luther and the Ninety-five Theses (1517)

In 1517, Martin Luther, a monk and professor at the University of Wittenberg in Germany, wrote a list of arguments, the Ninety-five Theses, objecting to the sale of indulgences. According to tradition he posted them on the door of the castle church on 31 October 1517, a common way to invite academic debate. Printers copied and distributed the theses, and within about a year they were being read across Germany.

Luther's objections soon widened into deeper theological claims. He taught that salvation comes through faith alone, often called sola fide, rather than through good works or payments, and that scripture alone, sola scriptura, not the pope or church tradition, is the ultimate authority for Christian belief. These were his positions in a dispute the Catholic Church rejected; the Church held that both faith and good works matter for salvation and that scripture must be read alongside church tradition and authority. In 1521, Luther was summoned to the Diet of Worms, an assembly of the Holy Roman Empire, where he refused to recant and was declared an outlaw. Protected by a sympathetic prince, he hid at Wartburg Castle and translated the New Testament into German, making scripture readable by people who knew no Latin. This lesson describes these ideas to explain the conflict, not to endorse either side.

The spread of Protestantism

Luther's break was only the beginning. Other reformers developed their own movements, and the word Protestant came to describe those who separated from Rome. In Geneva, the French reformer John Calvin built an influential system centered on the doctrine of predestination, the belief that God has already determined which souls will be saved. Calvin's Institutes of the Christian Religion (1536) shaped reformed churches across Europe, from the Netherlands to Scotland.

England's break followed a different path. In 1534, Parliament passed the Act of Supremacy, making the English monarch, Henry VIII, the head of a Church of England independent of the pope. Henry's split began as a political and dynastic dispute, because the pope would not annul his marriage, rather than as a doctrinal quarrel like Luther's, though Protestant ideas soon shaped the new church. By the mid-sixteenth century, western Christianity included Catholics, Lutherans, Calvinists, Anglicans, and smaller radical groups, each claiming to represent authentic Christian teaching.

The Catholic response: the Counter-Reformation

The Catholic Church did not stand still. Its response, known as the Counter-Reformation or Catholic Reformation, combined the defense of Catholic doctrine with internal reform. The centerpiece was the Council of Trent, which met in three sessions between 1545 and 1563. There, bishops reaffirmed core Catholic teachings that the reformers had challenged: that salvation requires both faith and good works, and that scripture and church tradition are both sources of authority. At the same time, the council addressed abuses. It did not abolish indulgences but forbade selling them, and it ordered reforms such as better training for priests. New religious orders, notably the Jesuits, spread Catholic teaching and education across Europe and beyond. The Counter-Reformation shows that reformation was not only a Protestant project; the Catholic Church reformed itself while rejecting Protestant theology. Describing both the Protestant and Catholic sides on their own terms is essential to understanding the period fairly.

Consequences: a divided Christendom

The Reformation permanently divided western Christianity, and the division had consequences far beyond church walls. Religious differences became entangled with politics and war. The Peace of Augsburg (1555) tried to settle the German lands with the principle cuius regio, eius religio, "whose realm, his religion," letting each prince choose Lutheranism or Catholicism for his territory. That compromise did not hold, and religious and political rivalries helped fuel the Thirty Years' War (1618-1648), one of the deadliest conflicts in European history, ended by the Peace of Westphalia in 1648.

Other effects were slower but lasting. The reformers' emphasis on reading scripture in the vernacular encouraged literacy and the spread of printed books, and competing churches invested in schools. The idea that an individual conscience could stand against a powerful institution influenced later political thought. The settlement of the religious wars strengthened the authority of states over churches, contributing to the modern nation-state. Historians debate how much of this Luther intended, which was very little, but the long chain of consequences is why the Reformation is treated as a turning point between the medieval and modern worlds.