SHELAH, SAHARON (1945– ), Israeli mathematician. Born in Jerusalem, Shelah received his Ph.D. in mathematics from the Hebrew University of Jerusalem (1969). He was simultaneously professor of mathematics at the Hebrew University and Rutgers University, New Jersey. Shelah's main research interests are in the sphere of mathematical logic, and especially model theory and set theory. His classification theory and the idea of proper forcing have applications of fundamental importance to cardinal arithmetic. He also solved many famous and previously intractable problems in algebra and topology. He was a prolific writer of original papers and influential books. His 1994 book, Cardinal Numbers, won the Bolyai Prize for the year 2000 of the Hungarian Academy of Sciences for the best mathematical monograph on original research, nominally awarded every five years but the first in modern times. His honors include the Wolf Prize (2001) for his work on mathematical logic and set theory.