 So far, we have argued that Peirce’s insight on relations pushed him to extend the territory of logic from monadic, non-relational, propositional logic to polyadic, relational, quantification logic. This is the beginning of modern logic as we know it. In this section, taking up a different angle of Peirce’s adventure—to extend forms of representation from symbolic systems to diagrammatic systems, we present a story where his two different kinds of extension—one from non-relations to relations and the other from symbolic to diagrammatic—are connected with each other.