The article highlights the points in common between Kant’s theory of biology and Canguilhem’s philosophy of medicine. It shows how these two conceptions contribute in complementary ways to a better understanding of freedom of action within the limits of biological naturality. Using Kant and Canguilhem as a starting point, an argument is put forward against biological reductionism—and for resistance against biopolitical instrumentalization of the life sciences for ideological-totalitarian purposes of homogenization and normalization.