Nuel Belnap

Nuel Dinsmore Belnap Jr. (May 1, 1930 – June 12, 2024) was an American logician and philosopher who 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. Born in Winnetka, Illinois, Belnap earned a BA from the University of Illinois and a PhD from Yale University, where his doctoral advisor was Alan Ross Anderson. Belnap worked as a programmer for the National Security Agency before his academic career. He developed a four-valued logic to address issues in classical logic, leading to contributions in paraconsistent logic. His significant works include "Entailment: The Logic of Relevance and Necessity" (with A. R. Anderson) and "The Logic of Questions and Answers" (with T. B. Steel Jr.). He was elected a Fellow of the American Academy of Arts and Sciences in 2008. Belnap died in Whitefield, New Hampshire, at the age of 94.