At the dawn of the sixteenth century, the Holy Roman Catholic Church found itself beset with internal problems. Its hierarchy was corrupt and disorganized. Wealthy families staffed the leadership positions of churches, bishoprics, and the Roman curia. These members of the clergy bought and sold clerical positions. Bishops controlled huge territories on behalf of the Church that increased their own revenues, and Church officials bought and sold indulgences. Meanwhile, the local clergy was not properly educated and did not make much effort to take care of their flocks. They seldom preached, instructed the young, or ministered to the other needs of their parishioners. Worse, they set a bad example. Some had drinking problems, and others kept mistresses.

Religious orders were no better off. War, political strife, and the Black Death had stymied the growth of monasteries. Discipline in monasteries had waned, and members were no longer concerned about social and cultural conditions in the country. Common worship and common meals had given way to the desire for private property.

The Renaissance popes, wealthy patrons of the arts and shrewd statesmen, saw the sorry state of affairs, but they were enjoying the status quo too much. The Lateran Council, which concluded in 1517, called for reforms that included adequate training of clergy; however, the pope at the time, Leo X (1475–1521) failed to support them.

The need for reform paved the way for Martin Luther (1483–1546), the founder of the Reformation movement that led to the birth of many Protestant faiths. A thoughtful, loyal Catholic and scholar, Luther became an Augustinian monk, studied theology, and eventually became a professor at the University of Wittenberg in Germany.

Introspective and depressive, Luther felt he was not worthy of being saved. But in 1513 he had a spiritual insight: Our faith in God's love is what qualifies us for salvation. Good works are secondary. Man is a sinful vessel, saved only because he is cloaked in God's love.

Luther preached his new vision, but he didn't make an impact until he began his campaign against the selling of indulgences, which — for the right price — promised the rich redemption from Purgatory. One of Luther's arguments was that the pope could not possibly have control over souls in Purgatory.

Principles of Protestantism

In addition to the concept of salvation in faith alone, Luther's other theological principles have remained central to most Protestant denominations:

• Scripture alone. The Bible, especially the New Testament, is the only infallible source and rule of faith; each individual should interpret the Scriptures as he or she sees fit. Nothing written after the New Testament by Christian saints and theologians can claim to have the same authority as the Bible.

• The universal priesthood of believers. No person needs to depend on mediation of a clergyman between him or her and God. Neither the papacy nor the hierarchy of the Church has any more divine authority than an ordinary Christian.

• Preaching of the Word. A primary responsibility of ministers is to preach the message of the Scriptures so as to best reach their audience. As a consequence of this thesis, Protestants condensed the liturgy to an exegesis of the Scriptures and communion and began to conduct services in their native tongues (rather than in Latin).

Luther's movement spread rapidly through Europe, where Protestant churches began to come under the protection of the secular government. Another reformer, John Calvin, built on Luther's credos and sent missionaries throughout Europe to preach and to organize communities. Switzerland, Scotland, parts of France, and the Netherlands all embraced Calvinism. Calvin's teaching upheld the objectively real presence of Jesus in the Eucharist and stressed this sacrament as a way for believers to relate to God. By the time Calvin, Luther, and other reformers had finished their preaching, half of all Europe was Protestant.