Exoteric knowledge and esoteric knowledge. Ludwik Fleck, pedigrees and the visualization of pathological heredity

In Genesis and Development of a Scientific Fact, Ludwik Fleck uses the concept of an "ideogram" to designate the representation of a thought style through an image, which condenses its features in graphic properties. Pedigrees are such ideograms used by scientists and health professionals on the one hand, patients and lay persons on the other hand. Building on Fleck's analysis of the relationships between esoteric circles and exoteric circles, this paper traces the transformation and uses of pedigrees in 20th century medicine. It suggests that pedigrees in eugenics, clinical medicine, human genetics, and molecular genetics have presented distinct and relatively stable characteristics, reflecting the changing boundaries and roles of esoteric and exoteric knowledge.