Kant’s notoriously unclear attempt to defend the regulative principle of systematic unity as the supreme principle of theoretical reason in the Appendix to the Transcendental Dialectic has left its status a source of controversy. According to the dominant interpretation, the principle ought to be understood as a methodologically necessary device for extending our understanding of nature. I argue that this reading is flawed. While it may correctly affirm that the principle is normative in character, it wrongly implies that it binds with mere hypothetical necessity. I offer novel grounds for thinking that if reason’s principle is normative, then it binds agents categorically instead.
