In our three-dimensional world, we are surrounded by illustrated and labeled surfaces. What role does the cultural technique of flattening play in our knowledge practices? What is the cognitive creativity of tables, texts, diagrams, and maps that are indispensable for understanding and science? Sybille Krämer examines how synoptic arrangements become witnesses to thought. She analyzes the epistemic power of the line as the root of diagrammatic thinking, traces of which can already be found in the epistemological theories of Plato, Descartes, Kant, and Wittgenstein. This gives rise to the contours of a diagrammatology, within which the orientational and imaginative power of visible, spatial schemas for recognition can be explored.