One of the central tenets of liberal individualism holds that property rights and citizenship rights are based in self-possession, which is often defined as an original ownership of one's own labor potential. In this short essay I propose that the concept of self-possession rests on a prior assumption that selves are possessable objects—an assumption that was generated, before and alongside liberal political theory, in the practice of Atlantic slave capitalism. I will first consider how John Locke formulates the theory of possessive individualism in one of the most-cited passages of his Second Treatise of Government (1690). To shed light on that theory's implications, I will turn to A Narrative of the Life and Adventures of venture, a Native of Africa (1798), which recounts how Venture Smith, an eighteenth-century man enslaved as a child, came to possess himself, quite literally, by purchasing himself. Smith's account illuminates the tacit precondition of Locke's self-possessing individual: to be owned, the self must first be alienated, entered into the market, “thingified.” Juxtaposing Locke and Smith provides a snapshot of a larger project, in which I argue that Enlightenment thought was founded on—not merely proximal to—the Atlantic imperial context out of which it arose.