Joseph Halpern

Joseph Yehuda Halpern (May 29, 1953 – February 13, 2026) was an Israeli-American-Canadian computer scientist and professor of computer science at Cornell University. His research primarily concerned reasoning about knowledge and uncertainty. Halpern graduated in 1975 from the University of Toronto with a B.S. in mathematics. He then pursued a Ph.D. in mathematics at Harvard University, which he completed in 1981 under the guidance of Albert R. Meyer and Gerald Sacks. He authored several books, including 'Actual Causality,' 'Reasoning about Uncertainty,' and 'Reasoning About Knowledge.' His significant contributions were recognized with numerous awards, including the 1997 Gödel Prize in theoretical computer science and the 2009 Dijkstra Prize in distributed computing. In 1993, he was elected a Fellow of the Association for the Advancement of Artificial Intelligence (AAAI) for his work on logics of knowledge and belief. From 1997 to 2003, Halpern served as the editor-in-chief of the Journal of the ACM. He was also inducted as a Fellow of the Association for Computing Machinery in 2002 and an IEEE Fellow in 2012. In 2011, he held a Senior Fellowship at the Zukunftskolleg at the University of Konstanz. In 2019, he was elected to the National Academy of Engineering for his methods in reasoning about knowledge, belief, and uncertainty, and their applications. Halpern also contributed to arXiv.org as the administrator for the Computing Research Repository. His notable students include Nir Friedman, Daphne Koller, and Yoram Moses. Halpern passed away on February 13, 2026.