Introduction

Among the most respected interpreters, there is virtual unanimity that in the third section of the Groundwork Kant intends to provide a justification or proof of the validity of the supreme principle of morality previously articulated in the other two sections. The problem dealt with in the third section is a result of the fact that the analytical or regressive-hypothetical method hitherto adopted can satisfy only “whoever holds morality to be something and not a chimerical idea without any truth” (Groundwork, 4:445). The question of the validity of the supreme principle of morality requires the synthetic use of pure practical reason, since it concerns a quid juris analog to the one dealt with in the Critique of Pure Reason regarding the pure concepts of the understanding and the a priori synthetic principles.

Nevertheless, among the interpreters, there is also virtual unanimity that Kant's attempt fails. In fact, Kant himself raises the specter of a kind of circle “from which, as it seems, there is no way to escape” (Groundwork, 4:449; my emphasis). So, in what follows, I will provide a reconstruction of the argument developed by Kant in the third section of the Groundwork and defend it against the overall criticism, paying particular attention to the objection of a hidden circle in it. However, since there is an agreement among the interpreters concerning Kant's intentions and the shortcomings of his enterprise, it would then be convenient, first of all, to put forward some arguments and passages of Kant's texts that could grant at least some initial plausibility to my proposal.