The Role of Existential Graphs in Peirce’s Philosophy

Nowadays, Peirce is mostly recognized as the founder of pragmatism and for his extensive theory of signs. Interestingly, in contrast to the contemporary estimation of his work, Peirce himself considered his system of existential graphs as the ‘luckiest find of my career’. This paper aims to clarify why Peirce placed his existential graphs into the very heart of his philosophy. Moreover, the design of the graphs as diagrammatic reasoning system, as well as the design of the transformation rules, can be explained with Peirce’s purpose in the development of his graphs. Diagrammatic reasoning is the only really fertile reasoning. If logicians would only embrace this method, we should no longer see attempts to base their science on the fragile foundations of metaphysics or a psychology not based on logical theory; and there would soon be such an advance in logic that every science would feel the benefit of it. Peirce, Prolegomena to an Apology For Pragmaticism, 1906