The issue of what is proper to nature, or life itself, is central to critical accounts of biomedicine and its complex interrelations with social, political and economic forces. These engagements, namely biopolitical accounts of medical practices and ethical-political critiques of biomedical discourse, grapple with the indistinction between the political and biological that biomedicine enacts. Making a significant contribution to both literatures, Ed Cohen’s A Body Worth Defending argues that the emergence of the concept of biological immunity signals the entry of politics into life itself and, as such, constitutes a concrete example of biopolitics. This article examines Cohen’s account of how the political becomes biological, and the view of life it assumes. Seeking to open up the question of biology, it draws on the work of Georges Canguilhem, and New Materialist accounts of matter–meaning entanglement, to offer a reading of knowledge and life, or politics and biology, as ontologically entangled.