 Peirce presented propositional logic, quantification logic, and modal logic in a graphical way, and invented three systems of Existential Graphs (EG)—Alpha, Beta, and Gamma, respectively. In spite of Peirce’s own evaluation of Existential Graphs as “my chef d’oeuvre”, EG had to wait to be understood for a half century until two philosophers—Don Roberts and Jay Zeman—produced their impressive work. In the 1980s, EG was receiving attention from new disciplines—computer science and artificial intelligence—thanks to John Sowa’s novel application of EG to knowledge representation in Conceptual Structure (1984). More recently, toward the end of the twentieth century interdisciplinary research on multi-modal reasoning has drawn our attention to non-symbolic systems (see, e.g., Barwise &amp; Allwein [eds] 1996 and Barwise &amp; Etchemendy 1991) and EG, not surprisingly, occupied the top of their list. In that context, Shin (2002) focused on differences between symbolic versus diagrammatic systems and suggested a new way of understanding the EG system, though this was criticized in Pietarinen 2006.