Presbyterianism refers to a number of Christian churches adhering to the Calvinist theological tradition within Protestantism, which are organized according to a characteristic Presbyterian polity. Presbyterian theology typically emphasizes the sovereignty of God, the authority of the Scriptures, and the necessity of grace through faith in Christ. Presbyterianism originated primarily in Scotland. Scotland ensured Presbyterian "church government" in the Acts of Union in 1707 which created "Great Britain". In fact, most Presbyterians found in England can trace a Scottish connection, and the Presbyterian denomination was also taken to North America mostly by Scots and Scots-Irish immigrants. The Presbyterian denominations in Scotland hold to the theology of Calvin and his immediate successors, although there is a range of theological views within contemporary Presbyterianism.
Modern Presbyterianism traces its institutional roots back to the Scottish Reformation. Local congregations are governed by Sessions made up of representatives of the congregation, a conciliar approach which is found at other levels of decision-making (Presbytery, Synod and General Assembly). Theoretically, there are no bishops in Presbyterianism; however, some groups in Eastern Europe, and in ecumenical groups, do have bishops. The office of elder is another distinctive mark of Presbyterianism: these are specially ordained non-clergy who take part in local pastoral care and decision-making at all levels. The office of deacon is geared toward the care of members, their families, and the surrounding community. In some congregations active elders and deacons serve a three-year term and then rotate off for at least a year. The offices of pastor, elder, and deacon all commence with ordination; once a person is ordained, he holds that title for the rest of his life. An individual may serve as both an elder and a deacon.
The roots of Presbyterianism lie in the European Reformation of the 16th century, with the example of John Calvin's Geneva being particularly influential. Most Reformed churches who trace their history back to Scotland are either Presbyterian or Congregationalist in government. In the twentieth century, some Presbyterians played an important role in the Ecumenical Movement, including the World Council of Churches. Many Presbyterian denominations have found ways of working together with other Reformed denominations and Christians of other traditions, especially in the World Communion of Reformed Churches. Some Presbyterian churches have entered into unions with other churches, such as Congregationalists, Lutherans, Anglicans, and Methodists