Protestantism encompasses the Christian churches that separated from Rome during the Reformation in the 16th century. This movement was initiated by an Augustinian monk, Martin Luther. The term Protestant was originally applied to followers of Luther, who protested at the Diet of Spires (1529) against the decree that prohibited all further ecclesiastical reforms. Other influential reformers included John Calvin, Ulrich Zwingli, and John Knox. Protestantism rejected attempts to tie God's revelation to earthly institutions and strictly adhered to the Word of God as sole authority in matters of faith and practice (sola scriptura). Central in the reformers' understanding of the biblical message is the justification of the sinner by faith alone. The church is understood as a fellowship, and the priesthood of all believers is stressed.
The Augsburg Confession (1530) was the principal statement of Lutheran faith and practice. It became a model for other Protestant confessions of faith. Major Protestant denominations include the Lutheran, Reformed (Calvinist), Presbyterian, and Anglican (Episcopalian). Innumerable sects and denominations sprang from these roots, including Quakers, Baptists, Pentecostals, Congregationalists, Methodists, and nondenominational assemblies.
Since the latter part of the 19th century, national councils of churches have been established in many countries, for example, the Federal Council of Churches of Christ in America in 1908. Churches of a particular denomination have joined in federations and world alliances, beginning with the Anglican Lambeth Conference in 1867.
Protestant missionary activity, particularly strong in the 19th century, resulted in the founding of many churches in Asia and Africa. The ecumenical movement, which originated with Protestant missions, aims at unity among Christians and churches.