Georg Kreisel

Georg Kreisel, born in Graz, Austria, on September 15, 1923, was a prominent mathematical logician of Austrian origin who spent significant parts of his career in the United Kingdom and the United States. His family sent him to the UK before the Anschluss in 1938 due to his Jewish background. He pursued mathematics at Trinity College, Cambridge, and during World War II, he engaged in military-related work. Kreisel notably never obtained a Ph.D. but was later awarded a Cambridge Sc.D. in 1962, a higher doctorate based on published research. His academic career included teaching positions at the University of Reading (1949–1954, 1957, 1959–1960), the Institute for Advanced Study (1955–1957), Stanford University (1958–1959, 1962–1985), and the University of Paris (1960–1962). He became a professor at Stanford University in 1962, where he remained until his retirement in 1985. Kreisel's main contributions were in logic, particularly proof theory, where his 'unwinding' program aimed to extract constructive content from non-constructive proofs. He was elected a Fellow of the Royal Society in 1966. Kreisel maintained close friendships with notable figures such as physicist Francis Crick and philosopher Ludwig Wittgenstein, who highly regarded his philosophical acumen. He also had a close relationship with novelist Iris Murdoch, who dedicated a novel to him and used him as inspiration for characters in her works. After retiring, Kreisel resided in Salzburg, Austria, where he passed away on March 1, 2015, at the age of 91. He also authored biographies of mathematicians like Kurt Gödel and Bertrand Russell.