Abstract

Kant argued that morality required a non-natural metaphysics for two main reasons. First, the necessity and universality inherent in the moral law itself could not, he believed, stem from any natural source, as the popular moral sense theory of the time had held, but must originate in a non-natural faculty of reason. Second, morality required that humans be able to act freely, yet this freedom could not exist in a nature governed by deterministic laws as the rationalists had thought. To solve these problems Kant used his theory of transcendental idealism, which stated that nature as experienced by humans is merely an appearance of a separate realm of things as they are in themselves. The pure faculty of reason and the free human will could both exist, therefore, in the non-natural noumenal realm of things in themselves. Kant's approach faces two problems. First, there are problems with his argument that the necessity of the moral law cannot stem from nature. Second, the metaphysics of transcendental idealism does not adequately capture human moral freedom because it separates the natural act itself from its non-natural free source. The two-aspect reading of transcendental idealism, which attempts to solve this second problem, is itself incoherent as a metaphysical thesis. Kant's thought contains, however, an alternative solution which uses the conception of the priority of practical reason and its resultant view of the natural world under a normative interpretation to encompass these controversial metaphysical issues while avoiding a non-natural metaphysics for morality.