As he developed his ideas, Luther gathered followers, who came to be called Protestants. The word Protestant derives from a “protest” drawn up by a small group of reforming German princes in 1529. At first Protestant meant “a follower of Luther,” but as many other reformers appeared, it became a general term for all non-Catholic western European Christians.

Catholics and Protestants disagreed on many issues. First, how is a person to be saved? Catholic teaching held that salvation is achieved by both faith and good works. Protestants held that salvation comes by faith alone, irrespective of good works or the sacraments. God, not people, initiates salvation. (See “Listening to the Past: Martin Luther, On Christian Liberty.”) Second, where does religious authority reside? Christian doctrine had long maintained that authority rests both in the Bible and in the traditional teaching of the church. For Protestants, however, authority rests in the Bible alone, and for a doctrine or issue to be valid, it has to have a scriptural basis. Third, what is the church? Protestants held that the church is a spiritual priesthood of all believers, an invisible fellowship not fixed in any place or person, which differed markedly from the Roman Catholic practice of looking to a clerical, hierarchical institution headed by the pope in Rome. Fourth, what is the highest form of Christian life? The medieval church had stressed the superiority of the monastic and religious life over the secular. Protestants disagreed and argued that every person should serve God in his or her individual calling.

Pulpits and printing presses spread the Protestant message all over Germany, and by the middle of the sixteenth century people of all social classes had rejected Catholic teachings and become Protestant. What was the immense appeal of Luther’s religious ideas and those of other Protestants?

Educated people and humanists were attracted by Luther’s ideas. He advocated a simpler personal religion based on faith, a return to the spirit of the early church, the centrality of the Scriptures in the liturgy and in Christian life, and the abolition of elaborate ceremonies — precisely the reforms the Christian humanists had been calling for. His insistence that everyone should read and reflect on the Scriptures attracted the literate middle classes, including many priests and monks who became clergy in the new Protestant churches. Luther’s ideas also appealed to townspeople who envied the church’s wealth and resented paying for it. After cities became Protestant, the city council taxed the clergy and placed them under the jurisdiction of civil courts.

Scholars in many disciplines have attributed Luther’s fame and success to the invention of the printing press, which rapidly reproduced and made known his ideas. Many printed works included woodcuts and other illustrations, so that even those who could not read could grasp the main ideas. Hymns were also important means of conveying central points of doctrine, as was Luther’s translation of the New Testament into German in 1523.

Luther worked closely with political authorities, viewing them as fully justified in reforming the church in their territories. He instructed all Christians to obey their secular rulers, whom he saw as divinely ordained to maintain order. Individuals may have been convinced of the truth of Protestant teachings by hearing sermons, listening to hymns, or reading pamphlets, but a territory became Protestant when its ruler, whether a noble or a city council, brought in a reformer or two to re-educate the territory’s clergy, sponsored public sermons, and confiscated church property. This happened in many of the states of the empire during the 1520s and then moved beyond the empire to Denmark-Norway and Sweden.