Scottish religion in the eighteenth century includes all forms of religious organisation and belief in Scotland in the eighteenth century. This period saw the beginnings of a fragmentation of the Church of Scotland that had been created in the Reformation and established on a fully Presbyterian basis after the Glorious Revolution. These fractures were prompted by issues of government and patronage, but reflected a wider division between the Evangelicals and the Moderate Party. The legal right of lay patrons to present clergymen of their choice to local ecclesiastical livings led to minor schisms from the church. The first in 1733, known as the First Secession and headed by figures including Ebenezer Erskine, led to the creation of a series of secessionist churches. The second in 1761 led to the foundation of the independent Relief Church.

In 1743, the Cameronians established themselves as the Reformed Presbyterian Church, remaining largely separate from religious and political debate. Of independent churches from England that were established in the seventeenth century only the Quakers managed to endure in to the eighteenth century. Baptist chapels were re-established in the middle of the century and, although Scotland initially appeared fertile ground for Methodism, it failed to expand as quickly as elsewhere in the Great Britain and Ireland. A number of minor Scottish sects developed, such as the Bereans, Buchanites, Daleites and Glassites.

Episcopalianism had retained supporters through the Wars of the Three Kingdoms and changes of regime in the seventeenth century. Since most Episcopalians gave their support to the Jacobite rebellions in the first half of the early eighteenth century, they suffered a decline in fortunes. The remoteness of the Highlands and the lack of a Gaelic-speaking clergy undermined the missionary efforts of the established church. The later eighteenth century saw some success, owing to the efforts of the SSPCK missionaries and to the disruption of traditional society. Catholicism had been reduced to the fringes of the country, particularly the Gaelic-speaking areas of the Highlands and Islands. Conditions grew worse for Catholics after the Jacobite rebellions and Catholicism was reduced to little more than a poorly run mission. There was Evangelical Revival from the 1730s, reaching its peak at the Cambuslang Wark in 1742. The movement benefited the secessionist churches who gained recruits.

The Kirk had considerable control over the lives of the people, with a major role in the Poor Law and schools and over the morals of the population. Strict Sabbatarianism was vital to Presbyterianism. The sermon was seen as central and the only participation by the congregation the singing of the psalms. Communion was the central occasion of the church, conducted infrequently, at most once a year, often taking a week of festivals as part of a communion season. In the second half of the century there were a series of reforms of church music connected to a choir movement. Episcopalians installed organs and hired musicians, following the practice in English parish churches. Catholic worship was deliberately low key, with musical accompaniment prohibited.

Church of Scotland

The religious settlement after the Glorious Revolution of 1688/9 adopted the legal forms of 1592, which instituted a fully Presbyterian kirk, and doctrine based on the 1646 Westminster Confession of Faith.J. D. Mackie, B. Lenman and G. Parker, A History of Scotland (London: Penguin, 1991), , pp. 298–9. The early eighteenth century saw the growth of "praying societies", who supplemented the services of the established kirk with communal devotions. These often had the approval of parish ministers and their members were generally drawn from the lower ranks of local society. Their outlook varied but they disliked preaching that simply emphasised the Law or that understood the gospel as a new law neonomianism, or that was mere morality, and sought out a gospel that stressed the Grace of God in the sense set out in the Confession of Faith. They often disliked the role of lay patronage in the kirk.Mackie, Lenman and Parker, A History of Scotland, p. 300. The theological division between neonomian and antineonomian tendencies in the kirk were highlighted by the Marrow Controversy. The Marrow of Modern Divinity was a mid-seventeenth century book with an antineonomian perspective that was reprinted in 1718 and promoted by Thomas Boston (1676–1732) and others. The book was condemned by the General Assembly, giving it widespread publicity. The decision was appealed by 12 "Marrow Men", but the repudiation was upheld in 1722 and although its supporters were not expelled, they were denied advancement and the controversy continued.D. Hart, Calvinism: A History (Yale University Press, 2013), .

There were growing divisions between the Evangelicals and the Moderate Party. While Evangelicals emphasised the authority of the Bible and the traditions and historical documents of the kirk, the Moderates tended to stress intellectualism in theology, the established hierarchy of the kirk and attempted to raise the social status of the clergy.Mackie, Lenman and Parker, A History of Scotland, pp. 303–4. From the 1760s the Moderates gained an ascendancy in the General Assembly of the Church. They were led by the historian William Robertson (1721–93), who became principal of the University of Edinburgh and then by his successor George Hill (1750–1819), who was professor at the University of Aberdeen. Evangelical leaders included John Willison (1680–1750), John McLaurin (1693–1754) and Alexander Webster (1707–84). The most important figure was John Erskine (1721–1803), who was minister of Old Greyfriars Church in Edinburgh from 1768 and for 26 years a friend and colleague to Robertson. He was orthodox in doctrine, but sympathised with the Enlightenment and supported reforms in religious practice. A popular preacher, he corresponded with religious leaders in other countries, including New England theologian Johnathan Edwards (1703–58), whose ideas were a major influence on the movement in Scotland.D. W. Bebbington, "Religious life: 6 Evangelism" in M. Lynch, ed., The Oxford Companion to Scottish History (Oxford: Oxford University Press, 2001), , pp. 515–16. Judged by the number of books printed in Scotland, Boston was the most popular theological writer in the movement.J. Yeager, Enlightened Evangelicalism: The Life and Thought of John Erskine (Oxford: Oxford University Press, 2011), , pp. 49–50.

Secession

The 18th century saw the beginnings of a fragmentation of the Church of Scotland that had its foundation in the Reformation. These fractures were prompted by issues of government and patronage, but reflected a wider division between the Evangelicals and the Moderate Party over fears of fanaticism by the former and the acceptance of Enlightenment ideas by the latter.J. T. Koch, Celtic Culture: a Historical Encyclopedia, Volumes 1–5 (London: ABC-CLIO, 2006), , pp. 416–7. Ecclesiastical patronage, the right of local lairds or other notables to appoint ministers to a parish, had been abolished at the Glorious Revolution, but it was reintroduced in the Church Patronage (Scotland) Act 1711, resulting in frequent protests from the kirk.

The First Secession was over the right to appoint in cases where a patron made no effort to fill a vacancy. The result was that a group of four ministers, led by Ebenezer Erskine, the minister of Stirling, formed a distinct "Associate Presbytery" in 1733, but were not forced from the kirk until 1740. This movement was initially very small, but was petitioned by the praying societies with requests for preaching, leading to rapid growth.M. Lynch, Scotland: A New History (London: Pimlico, 1992), , p. 399. Although its founding ministers were from Perthshire and Fife, the forty congregations they had established by 1740 were widely spread across the country, mainly among the middle classes of major towns. The Secessionists soon split among themselves over the issue of the burgess oath, which was administered after the 1745 rebellion as an anti-Jacobite measure, but which implied that the Church of Scotland was the only true church. The "burghers", led by Erskine, maintained that the oath could be taken, but they were excommunicated by an "anti-burgher" faction, led by Adam Gib, who established a separate General Associate Synod.Mackie, Lenman and Parker, A History of Scotland, p. 302. In the 1790s the Seceders became embroiled in the Old and New Light controversy. The "Old Lichts" continued to follow the principles of the Covenanters, while the "New Lichts" were more focused on personal salvation, considered the strictures of the Covenants as less binding and that a connection of the church and the state was not warranted.

The second break from the kirk was also prompted by issues of patronage. Minister Thomas Gillespie (1708–74) was deposed by the General Assembly in 1752 after he refused to participate in inducting a minister to the Inverkeithing parish, since the parishioners opposed the appointment. Gillespie was joined by two other ministers and they held the first meeting of the Presbytery of Relief at Colinsburgh in Fife in 1761. While evangelical in doctrine, the Relief Church did not maintain that it was the only true church, but stated that it was still in communion with the kirk and maintained contact with Episcopalians and Independents.Lynch, Scotland: A New History, p. 400. Like the Associate Presbytery, the movement was initially small, but benefited from the Evangelical Revival of the later eighteenth century, which helped it expand rapidly.G. M. Ditchfield, The Evangelical Revival (London: Routledge, 1998), , p. 91.

Episcopalianism

Episcopalianism had retained supporters through the civil wars and regime changes in the seventeenth century. Although the bishops had been abolished in the settlement that followed the Glorious Revolution, becoming "non-jurors", not subscribing to the right of William III and Mary II to be monarchs, they continued to consecrate Episcopalian clergy. Many clergy were "outed" from their livings, but the king had issued two acts of indulgence in 1693 and 1695, allowing those who accepted him as king to retain their livings and around a hundred took advantage of the offer.Mackie, Lenman and Parker, A History of Scotland, pp. 252–3. New "meeting houses" sprang up for those who continued to follow the episcopalian clergy. They generally prospered under Queen Anne and all but the hardened Jacobites would be given toleration in 1712.Mackie, Lenman and Parker, A History of Scotland, pp. 252–3 and 298-9. Since most Episcopalians gave their support to the Jacobite rebellion in 1715, they suffered a decline in fortunes. A number of the clergy were deprived and in 1719 all meeting houses where prayers were not offered for King George were closed. In 1720, the last surviving bishop died and another was appointed as "primus", without any particular episcopal see. After the Jacobite rising of 1745, there was another round of restrictions under the Toleration Act 1746 and the Penal Act 1748, and the number of clergy and congregations declined. The church was sustained by the important nobles and gentlemen in its ranks.