In 1517 a German monk and university professor named Martin Luther wrote a set of arguments against the sale of indulgences. Within weeks, printed copies were circulating across Germany. Within a few years, the Western church had split. The Protestant Reformation would probably have happened in some form without printing, but print shaped its speed, its scale and its character.

The Ninety-five Theses

Indulgences, as Level 2 noted, were documents sold by the church that promised to reduce punishment for sins. In 1517 a preacher named Johann Tetzel was selling them aggressively in Germany to raise money, partly for rebuilding St. Peter's Basilica in Rome. Luther, a professor at the small university of Wittenberg, objected that forgiveness could not be bought. On 31 October 1517 he sent the archbishop of Mainz his Ninety-five Theses, a list of propositions for academic debate. Tradition says he also nailed them to the door of the Castle Church in Wittenberg; historians debate whether that happened.

What clearly happened is that the theses were printed and reprinted, in Latin and then in German, in cities such as Nuremberg, Leipzig and Basel by the end of 1517. Luther had written for scholars, but print carried his ideas to a far wider public within weeks.

Luther the bestselling author

Luther quickly understood the power of print. He wrote short, punchy pamphlets in German, aimed at ordinary readers rather than theologians. His three great works of 1520 attacked the authority of the pope, the church's system of sacraments and the special status of the clergy. Printers rushed to publish him because his works sold. By some estimates, Luther's writings made up about a third of all German-language books sold in the first half of the 1520s, making him the first bestselling author of the print era.

Print allowed the movement to spread faster than authorities could stop it. When Luther was condemned by the pope in 1520 and declared an outlaw by the emperor at the Diet of Worms in 1521, his books were ordered burned. But there were too many copies, in too many cities, printed by too many presses, for any authority to destroy them all.

Pictures for those who could not read

Most people in Germany could not read, so pamphlets were often read aloud in homes, taverns and marketplaces. Printers also used woodcut images, which reached the illiterate directly. The painter Lucas Cranach the Elder, a friend of Luther, produced pamphlets contrasting scenes from the life of Christ with images of the pope, showing Christ humble and the pope greedy. Catholic writers answered with their own pamphlets and images, mocking Luther as a seven-headed monster. This was a war of propaganda, carried on by both sides with all the tools print offered.

The Bible in German

Luther believed every Christian should be able to read scripture. While hiding at Wartburg Castle after the Diet of Worms, he translated the New Testament from Greek into German. It was published in September 1522 and sold thousands of copies within months. The full Bible appeared in 1534. Luther's vivid, plain German, which he said he learned by listening to how mothers, children and ordinary people spoke in the market, helped shape a standard written German used across many dialects.

In England, William Tyndale translated the New Testament into English and had it printed abroad in 1526, since such translation was forbidden in England. Copies were smuggled in and burned by church authorities. Tyndale was executed for heresy in 1536, but much of his wording passed into the King James Bible of 1611.

The response

The Catholic Church responded with its own reforms and with controls on print. In 1559 Pope Paul IV issued the first papal Index of Prohibited Books, a list of works Catholics were forbidden to read. It was updated for four centuries and was abolished only in 1966. Protestant authorities, too, censored works they considered heretical. Europe entered a century of religious wars in which print was used to justify violence as well as to argue for reform.

Worked example: why Luther succeeded where others failed

Luther was not the first to challenge the church. The Czech reformer Jan Hus had made similar criticisms a century earlier and was burned at the stake in 1415. His movement survived in Bohemia but did not spread widely. Why did Luther's ideas spread so much further? Consider several factors.

• Print. Hus's writings existed only in manuscript. Luther's were printed in hundreds of thousands of copies.
• Language. Luther wrote in German for ordinary people, in short works that were cheap to print and buy.
• Protection. Frederick the Wise, ruler of Saxony, protected Luther. Hus had been promised safe conduct to the Council of Constance and was arrested anyway.
• Politics. German princes had their own reasons to resist the pope and the emperor, and many adopted the Reformation.
• Timing. Resentment of church corruption and Roman money demands was widespread.

Print was necessary but not sufficient. A message spreads when technology, language, protection and public mood all line up. That pattern explains many later movements too, from revolutionary pamphlets to social media campaigns.