In principle, the Metaphysics of Morals completes Kant’s exposition of pure practical reason’s capacities and obligations for moral choice and action, building on the conclusions of the Groundwork of the Metaphysics of Morals and the Critique of Practical Reason. Following the path cleared by these, the Metaphysics of Morals finally articulates the ramifications of the moral law into determinate kinds of moral duties and actions. This is at least how Kant introduces the text and its initial division into a doctrine of right and a doctrine of virtue, but the division announces a surprising change in the foundational structure of Kantian moral theory. Despite the doctrine of right’s newfound centrality, the nature of its relationship to the rest of Kant’s moral system is not explicated in anything like an explicit or decisive way. Although Kant presents right as a derivative of human freedom, his claims and remarks suggest several possible ways of understanding this relationship. Indeed, the argumentative mechanism that connects the doctrine of right to the rest of the practical philosophy is, it seems, at best obscure and at worst absent. This obscurity is testified to by the number and variety of existing attempts to reconstruct the connection of right to morality. Consequently, the grounding of right on a transcendental and not merely conventional basis is jeopardized.
I will argue that this obscurity arises from a point of unclarity in the text around the nature of external freedom, the kind of freedom that right specifically concerns. Contrary to some interpretations, I suggest that neither a devolution of right from the moral law itself, nor the analytic nature of right that Kant avers, suffice to explain the place of the doctrine of right. Instead, I will give an interpretation of the meaning of external freedom and evaluate its possible relationship to Kant’s more general concept of freedom. I will conclude that while right is analytically linked to outer freedom, this link is not sufficient to explain the place of the doctrine of right, which ultimately is grounded in Kant’s conception of noumenal freedom. By way of that connection, right should be understood as a consequence of the supreme value of autonomous moral law-giving, but only through an articulation of freedom into inner and outer. Once this enriched conception of freedom is unfolded, the transcendental basis of juridical law and standing can become intelligible.