Peirce developed two different concepts-"abduction" and "diagrammatic reasoning"-that are interesting for theories of creativity in mathematics, the sciences, and in learning. He defined "abduction" as the "inference" from surprising, or unexplained, observations to an explanatory hypothesis. However, he does not provide much to explain how the process of creating new hypotheses might be possible. In this contribution, I start from a remark by Peirce claiming that diagrammatic reasoning might

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... mehow be the foundation of abduction. Using an example from astronomy, I argue that at least one form of abduction is indeed based on diagrammatic reasoning: theoretic model abduction.