How did John Locke distinguish between the roles of church and state?

In his influential work A Letter Concerning Toleration, the English philosopher John Locke distinguished between the roles of church and state by defining their separate purposes and the methods they may legitimately employ.1

• The State: Locke argued that the government’s proper domain is the protection of "civil interests," which include life, liberty, health, and the possession of property. The state is empowered to use force and coercion to maintain peace, order, and the public good.12
• The Church: In contrast, the church is a voluntary association of individuals seeking the salvation of their souls. Its proper concern is the guidance of believers toward this spiritual end.1

Locke maintained that these realms must remain separate because their methods are fundamentally different: the state relies on coercion, while the church must rely on the "inward and full persuasion of the mind." He argued that because genuine religious belief requires sincere conviction, state-mandated worship is ineffective and unacceptable to God. Consequently, he advocated for religious toleration, asserting that the government should not use its power to resolve spiritual disagreements or enforce religious uniformity.1