BAR-HILLEL, YEHOSHUA (1915–1975), philosopher and theoretical linguist. Bar-Hillel was born in Vienna, educated in Germany, and after 1933, at the Hebrew University. He served in World War ii, and lost an eye fighting in the Israeli War of Independence. At the end of the war, he returned to the Hebrew University. He became a professor in 1961, a member of the Israel Academy of Arts and Sciences in 1963, and president of the International Union of History and Philosophy of Science in 1967. Bar-Hillel's early writings were concerned with the philosophy of mathematics, and culminated in the publication of his book with A.H. *Fraenkel, Foundations of Set Theory (1958). This sets out the major foundational approaches to mathematics and emphasizes their connection with broader philosophical issues. As distinct from Fraenkel's Platonism, Bar-Hillel's contributions stress that mathematical entities have only a pseudo-existence. Bar-Hillel's writings deal with the philosophy of language, philosophy of science, inductive logic, machine translation, mechanization of information retrieval, algebraic linguistics, and the semantics of natural languages. Some of these latter topics form the subject of his Language and Information (1964), which is concerned with the development of a science of language.