Meditating and Inquiring with Imagination: Leibniz, Lambert, and Kant on the Cognitive Value of Diagrams

Reasoning with diagrams is considered to be a peculiar form of rea-soning. Diagrams are often associated with imagistic representationsconveyed by spatial arrangements of lines, points, figures, or lettersthat can be manipulated to obtain knowledge on a subject matter.Reasoning with diagrams is not just ‘peculiar’ because reasoners usespatially arranged characters to obtain knowledge – diagrams appar-ently have cognitive surplus: they enable a quasi-intuitive form ofknowledge. The present paper analyses the issue of diagrams’ cog-nitive value by enquiring into the tradition of symbolic cognitiondeveloped by Leibniz, Lambert, and Kant. The proposal resultingfrom this enquiry is to question the idea that the cognitive value ofdiagrams lies solely in allowing evidence for inferences. The imagina-tive dimension of diagrams connects reasoning to doxastic attitudesof meditation and enquiry