The fact that Ludwik Fleck drew his inspiration from medicine has been largely overlooked, with the exception of a few scholars. Although Fleck considered his ideas applicable to all sciences, he always insisted on the specificity of medicine. To illustrate the usefulness of Fleck’s concepts for the history of medicine, three main ideas developed by Fleck are applied to the historical study of diabetes mellitus : first, that different and often divergent pictures of disease coexist within a given culture; second, (...) that scientific ideas circulate between ‘esoteric’ and ‘exoteric’ circles; and third, that scientific concepts are often incommensurable. The author also suggests that Fleck’s epistemology, like other scholars’, is loaded with ethical and political consequences. However, the link between an ‘open’ epistemology and political or ethical questions is more explicit in Georges Canguilhem’s pioneering work on the normal and the pathological . Indeed, Canguilhem and Fleck’s conceptions of disease have much in common, so that we can use Canguilhem’s work to bring out the hidden ethical and political issues in Fleck’s work. (shrink)