What Can a Diagram Do?

This paper traces the notion of the diagram in Deleuze’s philosophy and advances three main theses. First, Deleuze’s conception of the diagram reveals crucial connections to contemporary scholarship that treats it as a cognitive artefact. Second, the notion of diagram occupies a position of genuine philosophical significance within Deleuze’s system, being conceptually equivalent to other key concepts in his work, such as the virtual, the problem, and the idea. Third, the concept of diagram is emblematic of the peculiar and controversial way in which Deleuze approaches philosophy as an overtly metaphysical enterprise. To develop these claims, the paper first considers different disciplinary approaches that treat diagrams as cognitive artefacts with a genuinely generative, rather than merely representational, function (Sect. 2). It then examines examples of diagrams that Deleuze himself drew and incorporated into his philosophical texts (Sect. 3) and analyzes his explicit theorization of the concept of the diagram (Sect. 4), highlighting his machinic conception of diagrammatic behavior. Finally, it shows how this understanding reveals the specific way in which Deleuze collapses epistemology into ontology, emphasizing how diagrams—both in their general conceptual sense and in their specific graphic practice—provide a key instance of ideational phenomena diffused throughout the world (Sect. 5).