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 set down by John Calvin and other Reformation-era theologians. Calvinists broke from the Roman Catholic Church in the 16th century. Calvinists differ 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. As declared in the Westminster and Second Helvetic confessions, the core doctrines are predestination and election. 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. In the context of the Reformation, Huldrych Zwingli began the Reformed tradition in 1519 in the city of Zürich. His followers were instantly labeled Zwinglians, consistent with the Catholic practice of naming heresy after its founder. Very soon, Zwingli was joined by Martin Bucer, Wolfgang Capito, William Farel, Johannes Oecolampadius and other early Reformed thinkers. The namesake of the movement, French reformer John Calvin, converted to the Reformed tradition from Roman Catholicism only in the late 1520s or early 1530s as it was already being developed. The movement was first called Calvinism, referring to John Calvin, by Lutherans who opposed it. Many within the tradition find it either an indescriptive or an inappropriate term and would prefer the word Reformed to be used instead. Some Calvinists prefer the term Augustinian-Calvinism since Calvin credited his theology to Augustine of Hippo. The most important Reformed theologians include John Calvin, Huldrych Zwingli, 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, Gordon Clark, and R. C. Sproul were influential. Contemporary Reformed theologians include J. I. Packer, John MacArthur, Timothy J. Keller, David Wells, and Michael Horton. Reformed churches may exercise several forms of ecclesiastical polity; most are presbyterian or congregationalist, though some are episcopalian. Calvinism is largely represented by Continental Reformed, Presbyterian, and Congregationalist traditions. The biggest Reformed association is the World Communion of Reformed Churches with more than 100 million members in 211 member denominations around the world. There are more conservative Reformed federations such as the World Reformed Fellowship and the International Conference of Reformed Churches, as well as independent churches. Calvinism is named after John Calvin. It was first used by a Lutheran theologian in 1552. It was a common practice of the Roman Catholic Church to name what it viewed as heresy after its founder. Nevertheless, the term first came out of Lutheran circles. Calvin denounced the designation himself: Despite its negative connotation, this designation became increasingly popular in order to distinguish Calvinists from Lutherans and from newer Protestant branches that emerged later. The vast majority of churches that trace their history back to Calvin (including Presbyterians, Congregationalists, and a row of other Calvinist churches) do not use it themselves, since the designation 'Reformed' is more generally accepted and preferred, especially in the English-speaking world. Moreover, these churches claim to be—in accordance with John Calvin's own words—'renewed accordingly with the true order of gospel'. Since the Arminian controversy, the Reformed tradition—as a branch of Protestantism distinguished from Lutheranism—divided into two separate groups: Arminians and Calvinists. However, it is now rare to call Arminians a part of the Reformed tradition. While the Reformed theological tradition addresses all of the traditional topics of Christian theology, the word Calvinism is sometimes used to refer to particular Calvinist views on soteriology and predestination, which are summarized in part by the Five Points of Calvinism. Some have also argued that Calvinism as a whole stresses the sovereignty or rule of God in all things including salvation. First-generation Reformed theologians include Huldrych Zwingli (1484–1531), Martin Bucer (1491–1551), Wolfgang Capito (1478–1541), John Oecolampadius (1482–1531), and Guillaume Farel (1489–1565). These reformers came from diverse academic backgrounds, but later distinctions within Reformed theology can already be detected in their thought, especially the priority of scripture as a source of authority. Scripture was also viewed as a unified whole, which led to a covenantal theology of the sacraments of baptism and the Lord's Supper as visible signs of the covenant of grace. Another Reformed distinctive present in these theologians was their denial of the bodily presence of Christ in the Lord's supper. Each of these theologians also understood salvation to be by grace alone, and affirmed a doctrine of particular election (the teaching that some people are chosen by God for salvation). Martin Luther and his successor Philipp Melanchthon were undoubtedly significant influences on these theologians, and to a larger extent later Reformed theologians. The doctrine of justification by faith alone was a direct inheritance from Luther. John Calvin (1509–64), Heinrich Bullinger (1504–75), Wolfgang Musculus (1497–1563), Peter Martyr Vermigli (1500–62), and Andreas Hyperius (1511–64) belong to the second generation of Reformed theologians. Calvin's Institutes of the Christian Religion (1536–59) was one of the most influential theologies of the era. Toward the middle of the 16th century, the Reformed began to commit their beliefs to confessions of faith, which would shape the future definition of the Reformed faith. The 1549 Consensus Tigurinus brought together those who followed Zwingli and Bullinger's memorialist theology of the Lord's supper, which taught that the supper simply serves as a reminder of Christ's death, and Calvin's view that the supper serves as a means of grace with Christ actually present, though spiritually rather than bodily. The document demonstrates the diversity as well as unity in early Reformed theology. The remainder of the 16th century saw an explosion of confessional activity. The stability and breadth of Reformed theology during this period stand in marked contrast to the bitter controversy experienced by Lutherans prior to the 1579 Formula of Concord.