Ludwig Josef Johann Wittgenstein (; German: [ˈvɪtgənˌʃtaɪn]; 26 April 1889 – 29 April 1951) was an Austrian-British philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. From 1929 to 1947, Wittgenstein taught at the University of Cambridge. During his lifetime he published just one slim book, the 75-page Tractatus Logico-Philosophicus (1921), one article, one book review and a children's dictionary. His voluminous manuscripts were edited and published posthumously. Philosophical Investigations appeared as a book in 1953, and has since come to be recognised as one of the most important works of philosophy in the twentieth century. His teacher, Bertrand Russell, described Wittgenstein as "the most perfect example I have ever known of genius as traditionally conceived; passionate, profound, intense, and dominating".
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