One of the fundamental questions in post-Fregean philosophy is how to account for the normativity involved in assertoric claims once the traditional subject-object view of thinking is rejected. One of the more productive lines of inquiry in the contemporary literature attributes normativity to second nature, which is presented as a sui generis space of reason giving and receiving distinct from the space of nature studied by the natural sciences. In this paper I suggest an alternative account by drawing from Castoriadis’s philosophical interpretation of autopoiesis. For Castoriadis, the idea of second nature protects the modern conception of nature from undergoing the radical critique it requires, for it restricts normativity to the anthropic sphere. In contrast, he proposes an autopoietic account of the subject that grounds the capacity to know that one knows in the activity of the living being. Castoriadis demonstrates that the normativity of assertoric claims is not a vertical break from nature but rather a horizontal transformation of the biological capacity for self-referentiality.