Leon Albert Henkin (1921-2006) http://www.berkeley.edu/news/media/releases/2006/11/09_henkin.shtml Leon A. Henkin, a professor emeritus of mathematics at the University of California, Berkeley, who labored much of his career to boost the number of women and underrepresented minorities in the upper echelons of mathematics, died of natural causes at his Oakland home on Nov. 1. He was 85. Henkin came to UC Berkeley in 1953, having already established his reputation in the field of logic with a "brilliant" doctoral dissertation in which he produced a radically new proof of the fundamental Goedel completeness theorem, according to logician John W. Addison, UC Berkeley professor emeritus of mathematics. This theorem states that the axioms and rules of inference of basic ("first-order") logic are complete, that is, that they are sufficient to prove all logically valid sentences within the logic. "The proof was recognized by leading logicians to be extremely original as well as shorter and easier to understand than Gdel's original proof," said Addison. "It was based on a new technique, involving the use of so-called 'Henkin constants,' that became and remains one of the fundamental tools used in the branch of logic known as 'model theory,' now one of the four leading branches of mathematical logic." Henkin also brought the tools of algebra to the study of logic, co-authoring the major work "Cylindric Algebras" (1971) with J. Donald Monk and Alfred Tarski. The late Tarski, a UC Berkeley math professor and one of the great logicians, helped build the campus into what many consider the world's leading center of mathematical logic, and Henkin was his first major hire. Henkin was born in Brooklyn, N.Y., on April 19, 1921, the son of immigrant Russian Jews. He earned a B.A. in mathematics and philosophy from Columbia University in 1941, and an M.A. in 1942 and a mathematics Ph.D. in 1947 from Princeton University, where his dissertation supervisor was the famous logician Alonzo Church. Henkin served several years as vice chairman of the Department of Mathematics, three times as acting chairman, and from 1984-85 as chairman. From 1959-60, he served as the first chair of UC Berkeley's pioneering interdisciplinary Group in Logic and the Methodology of Science. And from 1973-75, he was associate director of the Lawrence Hall of Science, a science museum and education research center at UC Berkeley. Henkin is survived by his wife, Ginette (Potvin) Henkin of Oakland; sons, Julian of New York City and Paul of San Diego; and sister, Estelle Kuhn of New York City.