The Puritans were a significant grouping of English-speaking Protestants in the 16th and 17th-century. Puritanism in this sense was founded by some Marian exiles from the clergy shortly after the accession of Elizabeth I of England in 1559, as an activist movement within the Church of England. They were blocked from changing the system from within, but their views were taken by the emigration of congregations to the Netherlands and later New England, and by evangelical clergy to Ireland and later into Wales, and were spread into lay society by preaching and parts of the educational system, particularly certain colleges of the University of Cambridge. Puritans were mainly concerned with religious matters, and took on distinctive views on clerical dress and in opposition to the episcopal system, particularly after the 1619 conclusions of the Synod of Dort were resisted by the English bishops. They largely adopted sabbatarian views in the 17th century, and were influenced by millenialism. In alliance with the growing commercial world, the parliamentary opposition to the royal prerogative, and in the late 1630s with the Scottish Presbyterians with whom they had much in common, the Puritans became a major political force in England and came to power as a result of the First English Civil War. After the English Restoration of 1660 and the 1662 Uniformity Act, almost all Puritan clergy left the Church of England, some becoming nonconformist ministers, and the nature of the movement in England changed radically, though it retained its character for much longer in New England.
Puritans by definition felt that the English Reformation had not gone far enough, and that the Church of England was tolerant of practices which they associated with the Catholic Church. They formed into various religious groups advocating for greater “purity” of worship and doctrine, as well as personal and group piety. Puritans adopted a Reformed theology and in that sense were Calvinists (as many of their opponents were, also), but also took note of radical views critical of Zwingli in Zurich and Calvin in Geneva. In church polity, some advocated for separation from all other Christians, in favor of autonomous gathered churches, and these separatist and independent strands of Puritanism became significant in the 1640s, when the supporters of a presbyterian polity in the Westminster Assembly were unable to forge a new English national church.
The word “Puritan” was originally an alternate term for “Cathar” and was a pejorative term used to characterize them as extremists similar to the Cathari of France. Thus, scholars commonly use the term Precisianist in regard to the historical groups of England and New England. Currently, the designation “Puritan” is often expanded to mean any very conservative Protestant, or even more broadly, to evangelicals.