Born in Vienna into one of Europe's richest families, he inherited a fortune from his father in 1913. He initially made some donations to artists and writers and then, in a period of severe personal depression after the First World War, he 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 front line 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 as a hospital porter during World War II in London where he told patients not to take the drugs they were prescribed while largely managing to keep secret the fact that he was one of the world's most famous philosophers. He described philosophy 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.
A survey among American university and college teachers ranked the Investigations as the most important book of 20th-century philosophy, standing out as "the one crossover masterpiece in twentieth-century philosophy, appealing across diverse specializations and philosophical orientations." The Investigations also ranked 54th on a list of most influential twentieth-century works in cognitive science prepared by the University of Minnesota's Center for Cognitive Sciences. However, in the words of his friend Georg Henrik von Wright, he believed "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 was writing for people who would think in a different way, breathe a different air of life, from that of present-day men."
According to a family tree prepared in Jerusalem after World War II, Wittgenstein's paternal great-grandfather was Moses Meier, a Jewish land agent who lived with his wife, Brendel Simon, in Bad Laasphe in the Principality of Wittgenstein, Westphalia. In July 1808, Napoleon issued a decree that everyone, including Jews, must adopt an inheritable family surname, and so Meier's son, also Moses, took the name of his employers, the Sayn-Wittgensteins, and became Moses Meier Wittgenstein. His son, Hermann Christian Wittgenstein—who took the middle name "Christian" to distance himself from his Jewish background—married Fanny Figdor, also Jewish, who converted to Protestantism just before they married, and the couple founded a successful business trading in wool in Leipzig. Ludwig's grandmother Fanny was a first cousin of the famous violinist Joseph Joachim.
They had 11 children—among them Wittgenstein's father. Karl Otto Clemens Wittgenstein (1847–1913) became an industrial tycoon, and by the late 1880s was one of the richest men in Europe, with an effective monopoly on Austria's steel cartel. Thanks to Karl, the Wittgensteins became the second wealthiest family in Austria-Hungary, only behind the Rothschilds. As a result of his decision in 1898 to invest substantially in the Netherlands and in Switzerland as well as overseas, particularly in the US, the family was to an extent shielded from the hyperinflation that hit Austria in 1922. However, their wealth diminished due to post-1918 hyperinflation and subsequently during the Great Depression, although even as late as 1938 they owned 13 mansions in Vienna alone.