1771-1859

French mathematician who introduced the term duality into mathematics and founded the influential journal Annales de Mathematiques Pures et Appliquées. A duality is a symmetry in a mathematical theory such that if certain objects or relations are interchanged—such as line and point in projective geometry—all theorems remain valid. Gergonne's work had the philosophical bent of conceptual analysis, as in his work on definition theory, in which he made the distinction between implicit and explicit definitions.