The debates in moral philosophy that took place between the publication of Christian Wolff’s German Ethics (1720) and Kant’s Groundwork of the Metaphysics of Morals (1785) revolve around the concept of moral obligation. With the “principle of autonomy” (G 4:439), Kant gives these debates an entirely new direction. For the first time in the history of philosophy, the position is put forward that pure reason is the source of “absolute necessity” and of the obligation of the moral law. In this paper, Kant’s “principle of autonomy” is situated within the context of the debate concerning the concept of obligation. After a general introduction to this context, I consider how Samuel von Pufendorf and Wolff theorize obligation so as to specify the presuppositions that underlie the debate that took place in the following decades. Among the younger Wolffians, reference will be made to Johann August Eberhard as someone who reacts to new philosophical developments, for which Henry Home, Lord Kames, stands as a representative. Finally, I outline some of the unique characteristics of the Kantian conception of obligation.