This paper reconstructs and defends Kant's argument for the transcendental status of reason's principles of the systematic unity of nature in the Appendix to the Transcendental Dialectic. On the present account, these principles are neither mere methodological recommendations for conducting scientific inquiry nor do they have the normative force of categorical imperatives, two extant interpretations of Kant's discussion of reason in the Appendix. Instead, they are regulative yet transcendental principles restricted to theoretical cognition. The principles of the systematic unity of (...) nature count as transcendental in virtue of their role as conditions of the inferential articulation of empirical concepts. (shrink)