Wittgenstein, Ludwig (1889–1951), an Austrian who spent much of his life in England, being Professor of Philosophy at Cambridge from 1939 to 1947. He wrote two very influential philosophical classics, the second being a rejection of the first. The first was the Tractatus Logico-Philosophicus ("the Tractatus"). The second, published posthumously, was the Philosophical Investigations (Oxford, 1953) ("the Investigations"). Between the two there was a period in which he deserted philosophy, being "of the opinion that the problems have in essentials been finally solved" (Tractatus, p. 29).