An original and powerful philosopher, Ludwig Wittgenstein, an Austrian who finally became a naturalised British subject, came to England shortly before the First World War to study engineering. In 1912, bitten by logical and philosophical problems about the nature of mathematics, he migrated to Cambridge to work with Bertrand Russell. During that war, he was in the Austrian army and ended up a prisoner of war. In this period he wrote his one book, the famous Tractatus Logico-Philosophicus, of which a not quite reliable English translation was published in 1922. He taught in an Austrian village school for some time, during which he came into close philosophical touch with a few of the leading members of the Vienna Circle. In 1929 he came to Cambridge, where the importance of his ideas had been quickly recognised. In 1939 he became Professor. For part of the last war he was a hospital orderly at Guy’s Hospital. In 1947 he resigned his Chair. Besides the Tractatus, he published only one article.