Although in the last decades philosophers have increasingly paid attention to the life sciences, traditionally physics has dominated general philosophy of science. Does a focus on the life sciences and medicine produce a different philosophy of science and indeed a different conception of knowledge? Here I present a case study focussed on Georges Canguilhem. Canguilhem continued the philosophical tradition of what we now call historical epistemology, and always referred very closely to the philosophy of Gaston Bachelard. However, whereas Bachelard primarily studied the history of chemistry and physics, Canguilhem turned to the life sciences, medicine and psychiatry. I shall argue that some crucial differences in how they regarded norms, an issue seldom emphasised by Canguilhem himself or indeed by his critics, stem from the sciences on which they concentrated.