John Locke on the separation of Church and Magistrate (1689)

Found in The Works, vol. 5 Four Letters concerning Toleration
John Locke (1632-1704) was also known in his lifetime as a staunch defender of religious toleration. In this passage he calls for the complete separation of church and magistrate:
And the zealots hardly have patience to refrain from violence and rapine, so long till the cause be heard, and the poor man be, according to form, condemned to the loss of liberty, goods or life. Oh that our ecclesiastical orators, of every sect, would apply themselves, with all the strength of argument that they are able, to the confounding of men’s errours! But let them spare their persons. Let them not supply their want of reasons with the instruments of force, which belong to another jurisdiction, and do ill become a churchman’s hands. Let them not call in the magistrate’s authority to the aid of their eloquence, or learning; lest perhaps, whilst they pretend only love for the truth, this their intemperate zeal, breathing nothing but fire and sword, betray their ambition, and show that what they desire is temporal dominion.
Locke’s defence of religious toleration was very comprehensive for its time, even extending to Muslims, but unfortunately not to Catholics (they had sworn allegiance to a “foreign Prince”) or to atheists (who could not be trusted because they did not believe in the afterlife). He rejected the use of the power of the magistrate to enforce religious belief or practice because his sole purpose was to use coercive powers of the state to protect the lives, liberties, and properties of every individual. As long as people “mind only their own business” the magistrate has no interest in them whatsoever. Besides, Locke thought that to enforce outward conformity to certain religious practices was hypocritical as it left untouched “the inward persuasion of the mind.” There was also the “slippery slope argument” that if one allowed the zealous magistrate to enforce religious beliefs in the name of the welfare of the people, then what was to stop them interfering in every other aspect of a person’s life which affected their physical or spiritual wellbeing? Locke’s advice to the preacher was to make sure their “pulpits every-where sounded with this doctrine of peace and toleration”.