Part IV: Peirce's rules (Ad)


C.S. Peirce developed existential graphs, which is a way of expressing propositional calculus using graphs. Peirce also developed five rules of inference to go with his existential graphs, which can be used for reasoning with existential graphs.

Conceptual graphs are a further development and refinement of Peirce's existential graphs. In this chapter, we present Peirce's rules of inference, reformulated so that they fit conceptual graphs. Much of the discussion was inspired by Lukose and Kremer's online course in Knowledge Engineering. Errors are mine, of course (see About for who the author of these materials is).


First, we give some definitions that are necessary for formulating the rules precisely. Next, we present the rules themselves and give some evidence for their validity. Finally, we give an example of how the rules are used to prove a statement.

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