Abstract

John Neville Keynes uses a diagrammatic method, adapted of Euler’s diagrammatic method, in which the semantic content of a categorical judgment is associated to a proper subset of a set of basic diagrams. Different syllogistics are characterized by different sets of basic diagrams. We compare, by Keynesian diagrammatic method, three syllogistics as to validity of immediate inferences: the syllogistic without negative terms, the syllogistic with negative terms in which a term and its corresponding negative term complement each other in relation to the universe of discourse, and the syllogistic with negative terms in which a term and its corresponding negative term does not necessarily complement each other in relation to the universe of discourse.