Ludwig Josef Johann Wittgenstein (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 1929–1947, 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 by the end of the century it was considered an important modern classic. Philosopher Bertrand Russell described Wittgenstein as "the most perfect example I have ever known of genius as traditionally conceived; passionate, profound, intense, and dominating".Born in Vienna into one of Europe's richest families, he inherited a large fortune from his father in 1913. He gave some considerable sums to poor artists. In a period of severe personal depression after the first World War, he then gave away his entire fortune to his brothers and sisters. Three of his brothers committed suicide, with Wittgenstein contemplating it too. He left academia several times: serving as an officer on the frontline during World War I, where he was decorated a number of times for his courage; teaching in schools in remote Austrian villages, where he encountered controversy for hitting children when they made mistakes in mathematics; and working during World War II as a hospital porter in London, where he told patients not to take the drugs they were prescribed, and where he largely managed to keep secret the fact that he was one of the world's most famous philosophers. He described philosophy, however, as "the only work that gives me real satisfaction."His philosophy is often divided into an early period, exemplified by the Tractatus, and a later period, articulated in the Philosophical Investigations. The early Wittgenstein was concerned with the logical relationship between propositions and the world, and believed that by providing an account of the logic underlying this relationship he had solved all philosophical problems. The later Wittgenstein rejected many of the assumptions of the Tractatus, arguing that the meaning of words is best understood as their use within a given language-game.Wittgenstein's influence has been felt in nearly every field of the humanities and social sciences, yet there are diverging interpretations of his thought. In the words of his friend and colleague Georg Henrik von Wright: "He was of the opinion... that his ideas were generally misunderstood and distorted even by those who professed to be his disciples. He doubted he would be better understood in the future. He once said he felt as though he were writing for people who would think in a different way, breathe a different air of life, from that of present-day men."