A Letter Concerning Toleration, in the history of political philosophy, an important essay by the English philosopher John Locke, originally written in Latin (Epistola de Tolerantia) in 1685 while Locke was in exile in Holland and first published anonymously in both Latin and English (in a translation by William Popple) upon Locke’s return to England in 1689. A Letter Concerning Toleration greatly influenced the development of the modern concept of the separation of church and state, which is entrenched in a number of modern constitutions.
A Letter Concerning Toleration advocated for greater religious toleration during a period marked by dramatic and often violent religious and sectarian strife in Europe. In Locke’s England, Roman Catholics and Protestant dissenters were effectively barred from holding political office by the Test Act of 1673 (which conditioned public office on the reception of Holy Communion according to the rites of the Church of England), despite efforts by supporters of James II—the king of England, Scotland, and Ireland from 1685 to 1688—to have it repealed. Across the English Channel, in France, the rights of the Huguenots (French Protestants) were severely curtailed by King Louis XIV’s revocation in 1685 of the Edict of Nantes, which had previously recognized Protestants’ civil rights and freedom of conscience.
According to Locke, religious intolerance and persecution result from a lack of understanding of the distinction between the realms of religion (the proper domain of the church) and civil affairs (the proper domain of government). The government should not encroach upon religious liberty, just as religious leaders and believers should not seek to use the power of the state to resolve spiritual disagreements.
Locke argued in A Letter Concerning Toleration that the proper realm of government concerns “civil interests,” or the preservation of peace, order, and the people’s earthly well-being (in his own words, “life, liberty, health, and indolency of body; and the possession of outward things, such as money, lands, houses, furniture, and the like”). The citizenry, in a hypothetical compact, has entrusted the state (and the legitimate government in power) with this responsibility, along with the right to use force and coercion when necessary. For Locke, the government’s purview extends only to these civil interests and not to religious affairs. Therefore, the government should not discriminate based on religious belief or make laws specific to religious institutions. A Letter Concerning Toleration contrasts the civil interests that are the proper concern of government with the care of immortal souls and their guidance to salvation, which are the proper concern of religion. It is important to note that Locke did not oppose the right of members of government to express religious opinions: they can do so as individuals seeking to influence others through uncoerced persuasion, he argued, but they can not do so through laws or state power.
Locke’s defense of toleration is not grounded in ethical relativism. He recognized only “one truth, one way to heaven” but argued that this path is to be pursued by following one’s conscience, not through state power and coercion. A church, for Locke, is a free and voluntary association seeking salvation through collective worship. Although a person could be forced to make religious statements or perform religious rituals, such coercion would not advance—but would rather impede—the religious pursuit of salvation, since dishonest worship, unmoved by the “inward and full persuasion of the mind,” would be unacceptable to God. Because freedom of conscience is at the core of every genuine religious pursuit for Locke, toleration represents not only a dividing line between the realms of religion and government but also the chief distinguishing characteristic of the “true Church.” The distinction between the legitimate realms of government and religion is founded not only on their different purposes (civil interests versus salvation) but also on the different types of power they can rely upon (coercion versus persuasion of the mind).
Locke’s defense of religious toleration is not unconditional or without exception. A Letter Concerning Toleration specifically excludes two groups: Roman Catholics and atheists. Such exclusion or intolerance is justified, according to Locke, only when religious beliefs, or the absence thereof, pose a challenge to civil authority or are antithetical to the very existence of civil society. In the case of Roman Catholics, their submission to the authority of the pope (a spiritual but also political authority) was regarded by Locke as a direct challenge to the authority of secular rulers. As for atheists, Locke was convinced that their disbelief in God means that they can not be trusted to uphold any promise or covenant.
As a defense of religious freedom, A Letter Concerning Toleration is aligned with Locke’s other major works, which address the theme of human freedom as it pertains to other areas of life—namely, political freedom in the Two Treatises of Government (1689) and economic freedom in Some Considerations of the Consequences of the Lowering of Interest, and Raising the Value of Money (1692).