This article considers Ottobah Cugoano’s philosophical response to the moral and legal contradictions of the practice of human trafficking in his Thoughts and Sentiments on the Evil and Wicked Traffic of the Slavery and Commerce of the Human Species (1787). It analyses Cugoano’s critique of the origins of slavery in general and the practices of ancient slavery, from which seventeenth-century proslavery advocates drew political, theological, and moral justifications of the African slave trade. According to Cugoano’s analysis, there is a necessary (...) moral dependency of the laws of civilization (positive law) on natural law. This distinction has significant philosophical and ethical ramifications that extend beyond the debate over abolition in Cugoano’s time, specifically ramifications for conceptions of slavery in the early modern tradition of natural law theory. (shrink)