TARSKI, ALFRED (1902–1983), mathematical logician and founder of logical semantics. Born Teitelbaum in Warsaw, Poland, he studied logic at Warsaw University, a course disrupted by the events of World War I. In 1923 he changed his name to Tarski and became a Roman Catholic. Despite his growing international reputation, his academic advancement in Poland was slow. The Germans invaded Poland while he was attending a Harvard conference; he remained in the U.S. After prestigious but temporary appointments, he joined the University of California at Berkeley in 1942, becoming professor of mathematics in 1949. He remained at Berkeley for the rest of his career. Tarski was a logician ranked by his peers as the equal of Aristotle, Frege, and Godel. He pioneered the field of metamathematics. His most important contribution to logic is the semantic method, which allows a more exacting study of formal languages and especially the concept of truth. He also contributed to algebra and measure theory. His precise, energetic but at times acerbic teaching was enthusiastically received in the department he established at Berkeley and internationally as a visiting professor. His publications include An Introduction to Logic, which has been translated into many languages including Hebrew in 1957, and many monographs on basic mathematics and mathematical logic, as well as his collected papers (edited by Steven R. Givant and Ralph N. McKenzie). His many honors include election to the U.S. National Academy of Sciences and the British Academy.