When it was first brought to light in 2010, an anonymously authored, unpublished document from 1690, Proposals for the propagating of the Christian Religion, and Converting of Slaves whether Negroes or Indians in the English plantations, appeared to support claims for an emerging humanitarian sensibility among Christian antislavery reformers in seventeenth-century England. This article argues that Scottish Covenanter, colonizer, and enslaver William Dunlop was the author of these proposals. Dunlop's authorship casts them in a new light, showing the complex ways Christianity and slavery were entangled in this period and the challenges Reformed Protestants faced in their attempts to disentangle them. Dunlop's Reformed background and experience in the Presbyterian resistance movement during the “killing times” of the early 1680s led him to view slavery as anti-Christian tyranny and liberty as the will of God. But during his time in Carolina he was deeply implicated in enslaving illegally seized Christian Indian captives, African chattel slaves, white indentured servants seeking freedom in Spanish Catholic Florida, and even fellow Covenanters banished to the plantations for their resistance to episcopacy. Dunlop's proposals emerged from these dual contexts. They tried and failed to imagine a form of Christian slavery that gave enough freedom to enslaved people to lead authentic Christian lives, showing instead that Christianity and slavery were incompatible and offering reformers only a stark choice: not Christian slavery, but Christianity or slavery.