Calvinism (also called the Reformed tradition, Reformed Christianity, Reformed Protestantism, or the Reformed faith) is a major branch of Protestantism that follows the theological tradition and forms of Christian practice of John Calvin and other Reformation-era theologians.
Calvinists broke with the Roman Catholic Church but differed from Lutherans on the real presence of Christ in the Eucharist, theories of worship, and the use of God's law for believers, among other things. Its basic principle is that the Bible is to be interpreted by itself, meaning the parts that are harder to understand are examined in the light of other passages where the Bible is more explicit on the matter. The term Calvinism can be misleading, because the religious tradition which it denotes has always been diverse, with a wide range of influences rather than a single founder. The movement was first called Calvinism by Lutherans who opposed it, and many within the tradition would prefer to use the word Reformed.
Early influential Reformed theologians include Ulrich Zwingli, John Calvin, Martin Bucer, William Farel, Heinrich Bullinger, Peter Martyr Vermigli, Theodore Beza, and John Knox. In the twentieth century, Abraham Kuyper, Herman Bavinck, B. B. Warfield, J. Gresham Machen, Karl Barth, Martyn Lloyd-Jones, Cornelius Van Til, and Gordon Clark were influential. Contemporary Reformed theologians include J. I. Packer, John MacArthur, R. C. Sproul, Timothy J. Keller, John Piper, David Wells, and Michael Horton.