Belnap became an assistant professor at Yale. He recalled hiring
Jon Barwise and John Wallace as research assistants. "The way we worked when we worked together was cheek by jaw. We just sat down and wrote sentences together." Known as the
principle of explosion in
classical logic, the four-valued logic provides a basis for
paraconsistent logic to avoid this pathology of two-valued logic. In 1976 Belnap and T. B. Steel Jr. published
The Logic of Questions and Answers as a timely contribution to
erotetics. Beyond
propositional logic, they noted that the evolving
databases make possible "dossier files on individuals" (page 146) leading to the "problem of
privacy in record keeping." The book included a 45-page annotated bibliography of erotetics, sectioned by philosophy, linguistics, automatic question-answering, and pedagogy, compiled by
Hubert Schleichert and Urs Egli. On sabbatical, Belnap was visiting professor at the
University of California, Irvine and at
Indiana University Bloomington, in the falls of 1977, 1978, 1979 with Jon Michael Dunn. In 1982 at
Stanford's
Center for Advanced Studies in the Behavioral Sciences, and in 1996 at
Leipzig, Centrum für Höhere Studien with Heirich Wansing. He was a founding member of the Society for Exact Philosophy, which collaborated with Canadians such as
Mario Bunge. Belnap has served as referee for many academic papers. He was elected a Fellow of the
American Academy of Arts and Sciences in 2008. ==Personal life and death==