Leon Henkin

Leon Albert Henkin (1921 to 2006) was an American logician whose work strongly shaped the development of logic, particularly the theory of types. Born in Brooklyn, New York, to a Jewish family that had emigrated from Russia, he studied at Columbia University and then at Princeton, where he worked under Alonzo Church. He spent his career at the University of California, Berkeley, where with Alfred Tarski he directed the Group in Logic and the Methodology of Science. He is best known for his completeness proofs of formal systems such as type theory and first-order logic, introducing general models, now called Henkin models, as a new semantics that gives type theory and second-order logic a complete deductive calculus. He also worked on cylindric algebras with Tarski and Donald Monk, and took part in projects to teach mathematics and to support women and minority groups entering mathematical careers.