The Puritans were a significant group of English Protestants in the 16th and 17th centuries, including, but not limited to, English Calvinists. Puritanism in this sense was founded by some Marian exiles from the clergy shortly after the accession of Elizabeth I of England in 1558, as an activist movement within the Church of England. , based on the assumption that hedonism and puritanism are antonyms. Historically, the word was used pejoratively to characterise the Protestant group as extremists, similar to the Cathars of France and, according to Thomas Fuller in his Church History, dated back to 1564. Archbishop Matthew Parker of that time used it and "precisian" with the sense of the modern "".
Puritans were blocked from changing the established church from within, and severely restricted in England by laws controlling the practice of religion. Their views, however, were transported 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 and parts of the educational system, particularly certain colleges of the University of Cambridge. They 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 millennialism.
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 (1642–46). After the Restoration of 1660 and the 1662 Uniformity Act, almost all Puritan clergy left the Church of England, some becoming nonconformist ministers. The nature of the movement in England changed radically, although it retained its character for a much longer period in New England.
Puritans, by definition, felt that the English Reformation had not extended far enough, and that the Church of England was tolerant of practices which they associated with the Catholic Church. They formed, and identified with, various religious groups advocating 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 were many of their earlier opponents), but they 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 favour of autonomous gathered churches. These separatist and independent strands of Puritanism became prominent in the 1640s, when the supporters of a Presbyterian polity in the Westminster Assembly were unable to forge a new English national church.