A Letter Concerning Toleration by John Locke was originally published in 1689. Its initial publication was in Latin, though it was immediately translated into other languages. Locke's work appeared amidst a fear that Catholicism might be taking over England, and responds to the problem of religion and government by proposing religious toleration as the answer. This "letter" is addressed to an anonymous "Honored Sir": this was actually Locke's close friend Philipp van Limborch, who published it without Locke's knowledge.
In the wake of discovery of the Rye House Plot and Charles II's persecution of the Whigs, Locke fled England to Amsterdam, Holland in September 1683. Throughout his life, Locke had taken an interest in the debate about religious toleration. The question was much debated in Holland during Locke's stay and in October 1685 Louis XIV of France Revoked the Edict of Nantes that had guaranteed religious toleration for French Protestants.
In Holland, Locke met Philipp van Limborch, a Professor of Divinity, and it was to be a discussion with Limborch that persuaded Locke to temporarily put aside his work on An Essay Concerning Human Understanding and put forth his ideas on toleration. Locke wrote the Letter during the winter of 1685-86.
One of the founders of Empiricism, Locke develops a philosophy that is contrary to the one expressed by Thomas Hobbes in Leviathan, in supporting toleration for various Christian denominations. Hobbes did allow for individuals to maintain their own religious beliefs as long as they outwardly expressed those of the state, however, and it has been argued that Locke's rejection of Catholic Imperialism was the ultimate basis for his rejection of government's interest in spiritual salvation.