Nuel Belnap

Nuel Dinsmore Belnap Jr. (; May 1, 1930 – June 12, 2024) was an American logician and philosopher who has made contributions to the philosophy of logic, temporal logic, and structural proof theory. He taught at the University of Pittsburgh from 1963 until his retirement in 2011.

Early life and education Belnap was born on May 1, 1930. He attended New Trier High School in Winnetka, Illinois, and earned a Bachelor of Arts degree from the University of Illinois.

Alan Ross Anderson and Belnap began to discuss relevant implication. In 1960 Anderson told Belnap to write up the work he had done on relevance logic, and this was Belnap's PhD dissertation at Yale (entitled The Formalization of Entailment). The dissertation was published through Omar Kayam Moore at Office of Naval Research, Group Psychology Branch.

Career 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.

In 1992, Belnap published Branching space-time, which offers a logical framework attempting to bridge relativity and quantum indeterminism, and offers an interpretation to EPR-type experiments.

He was elected a Fellow of the American Academy of Arts and Sciences in 2008.

Personal life and death Belnap had three sons and a daughter with his first wife, Joan Gohde Belnap. He died in Whitefield, New Hampshire on June 12, 2024, at the age of 94.

Selected works 1975: (with Dorothy L. Grover & Joseph L. Camp) "The Prosentential Theory of Truth", Philosophical Studies 27(1): 73–125 1993: (with Anil Gupta) The Revision Theory of Truth, MIT Press 2001: (with Ming Xu and Michel Perloff) Facing the Future: agents and choices in our indeterministic world, Oxford University Press .