Philosopher, born in Vienna. He studied engineering at Berlin and Manchester, then became interested in mathematical logic, which he studied under Russell (1912--13). While serving in the Austrian army in World War 1, he wrote the Tractatus logico-philosophicus (1921), in which he argued that an adequate account of language must recognize that any sentence is a picture of the fact it represents, and that any thought is a sentence. In 1929 he began lecturing at Cambridge, submitting the Tractatus as his doctoral dissertation. He worked at hospitals in London and Newcastle upon Tyne during World War 2, returned to Cambridge afterwards, and resigned his chair in 1947. Between 1936 and 1949 he worked on the Philosophische Untersuchungen (1953, Philosophical Investigations), in which he rejected the doctrines of the Tractatus, claiming that linguistic meaning is a function of the use to which expressions are put, or the "language games' in which they play a role. He became a naturalized British subject in 1938.