Georg Kreisel (1923-2015)

Georg Kreisel (September 15, 1923 in Graz – March 1, 2015 in Salzburg) was an Austrian-born mathematical logician who studied and worked in Great Britain and America. Kreisel came from a Jewish background; his family sent him to England before the Anschluss, where he studied mathematics at  Trinity College, Cambridge  and then, during World War II, worked on military subjects. After the war he returned to Cambridge and received his doctorate. He taught at the  University of Reading  until 1954 and then worked at the   Institute for Advanced Study  from 1955 to 1957. Subsequently he taught at  Stanford University  and the  University of Paris . Kreisel was appointed a professor at Stanford University in 1962 and remained on the faculty there until he retired in 1985. Kreisel worked in various areas of logic, and especially in proof theory, where he is known for his so-called "unwinding" program, whose aim was to extract constructive content from superficially non-constructive proofs. Kreisel was elected to the  Royal Society  in 1966; Kreisel remained a close friend of  Francis Crick  whom he had met in the Royal Navy during WWII. While a student at Cambridge, Kreisel was the student most respected by  Ludwig Wittgenstein Ray Monk  writes, "In 1944--when Kreisel was still only twenty-one--Wittgenstein shocked  Rush Rhees  by declaring Kreisel to be the most able philosopher he had ever met who was also a mathematician." Kreisel was also a close friend of the Anglo-Irish philosopher and novelist  Iris Murdoch . They met at Cambridge in 1947 during Murdoch's year of study there. Peter Conradi reports that Murdoch transcribed Kreisel's letters into her journals over the next fifty years. According to Conradi, "For half a century she nonetheless records variously Kreisel's brilliance, wit and sheer 'dotty' solipsistic strangeness, his amoralism, cruelty, ambiguous vanity and obscenity." Murdoch dedicated her 1971 novel  An Accidental Man   to Kreisel and he became a (partial) model for several characters in other novels, including Marcus Vallar in  The Message to the Planet   and Guy Openshaw in  Nuns and Soldiers . After retirement Kreisel lived in Salzburg, Austria. He wrote several biographies of mathematicians including  Kurt Gödel Bertrand Russell  and   Luitzen Egbertus Jan Brouwer