I argue that by considering Kant’s engagement with previous theorists of natural right, we can gain a clearer understanding of how he transformed the discipline from its foundations. To do this, I focus my analysis on Kant’s (critical) reception of two models of natural right with which he was very familiar: one from Alexander Baumgarten’s Elements of First Practical Philosophy [Initia philosophiae practicae primae], the other from Gottfried Achenwall’s Natural Law [Ius naturae]. The Initia served as a basis for Kant’s (...) lectures on moral philosophy for over three decades and may thus be considered as having played an important role in shaping his practical philosophy as a whole. Achenwall’s Ius naturae was the textbook that Kant employed in his lectures on natural right for over two decades. I argue that Kant distances himself from previous models of natural right in three main regards: the identification of moral laws with laws of nature, the normative connection between the principles of right and a natural end, and the place of God as the author of moral laws. I then briefly discuss what Kant retains of Baumgarten’s and Achenwall’s models of natural right. Kant’s Metaphysics of Morals preserves the view that a rational doctrine of right belongs to a broader systematic doctrine that comprehends the entire system of duties. I address the question of the division of the Sittenlehre into two branches and claim that, whereas Kant did not consider Baumgarten’s answer to the problem of distinguishing juridical from ethical principles to be satisfactory, he found a key piece of his own resolution in Achenwall’s Ius naturae, namely the definition of right as a power to coerce. (shrink)