Diagrammatic Logic of Existential Graphs: A Case Study of Commands

Abstract

Diagrammatic logics have advantages over symbolic cousins. Peirce thought that logical diagrams (Existential Graphs, EG) are capable of “expression of all assertions”, as our reason is no longer limited to the “line of speech” (MS 654). This paper points out one such value: the economy resulting from combining multi-dimensional diagrams with multi-modal features. In particular, EGs are well-suited for representing and reasoning about non-declarative assertions, such as questions (interrogatives, vert), commands (e.g., imperatives, vair) and the compelled (potent). An advantage over symbolic-logical counterparts is multi-dimensionality that entitles recognition of non-declarative moods in an instantaneous fashion: there is no need to attune to the phonetics of expressions. The paper suggest an application of diagrammatic logic of commands to the cases where (i) minimal reaction time to commands is of essence, (ii) a full comprehension of the meaning of imperatives (‘search for their objects’) is needed, and (iii) an effective discrimination of commands from other non-declarative moods is critical.