peer reviewedIn this article I examine the perspectives of Charles Sanders Peirce, Gilles Deleuze, and Nelson Goodman on diagrams in order to assess the variety of meanings of diagrammatic reasoning, form, and manipulation. I argue that diagrammatic reasoning may not only guide the understanding of the functioning of schemas, graphs, and chains of equations, but also—as I show in this article—the functioning of scientific images, photographs, and artistic paintings. More precisely, I focus on the relationship between the concept of diagram, the composite photographs by Francis Galton studied by Charles Sanders Peirce, works of art such as the paintings by Francis Bacon studied by Gilles Deleuze, and scientific images (especially agg...