How did political economy conceive slavery during the eighteenth-century? This article seeks to question how dominant political economy explains slavery using the notion of “dependence” which constitutes a common reference in the second half of the XVII^th century and during the XVIII^th century in order to think about politics and economics. This notion which belongs to the natural right tradition is taken up by political economy for analysing work ties and wage-earner relationship. It is also used to approach slavery which in this perspective is nothing else that a particular aspect of dependence ties. Jean-François Melon’s Essai sur le commerce (1734) is more accurately studied. This book belongs to the tradition of political economy and it illustrates how slavery was conceived mobilising natural right and the concept of subordination. The article ends studying how slavery supporters used this kind of argument for justifying servitude.