Reason Jean Piaget wrote three short papers shortly before his death in 1980 Paper I: Scientific Report on Work during 1978–1979. Paper II: Reason as Objective of the Understanding. Paper III: Reason: Introduction. Each is probably incomplete, Papers II and III definitely so. These papers were intended as a contribution to his 1979–1980 research project “Reason,” here translated into English for the first time. Their central argument is distinctive. It amounts to Piaget's final statement of his empirical model of normative reason as a mechanism intrinsic to the construction of knowledge during children's cognitive development.