Born in Vienna, Ludwig Josef Johann Wittgenstein was educated at Linz and Berlin University. In 1908 he went to England, registering as a research student in engineering at the University of Manchester. There he studied Bertrand Russell's (see also Vol. 5) Principles of Mathematics by chance and decided to study with Russell at Cambridge University. From 1912 to 1913, he studied under Russell's supervision and began to develop the ideas that crystallized in his Tractatus. With the outbreak of World War I, he returned home and volunteered for the Austrian Army. During his military service, he prepared the book published in 1921 as the Tractatus, first translated into English in 1922 by C. K. Ogden. Wittgenstein emerged as a philosopher whose influence spread from Austria to the English-speaking world. Perhaps the most eminent philosopher during the second half of the twentieth century, Wittgenstein had an early impact on the members of the Vienna Circle, with which he was associated. The logical atomism of the Tractatus, with its claims that propositions of logic and mathematics are tautologous and that the cognitive meaning of other sorts of scientific statements is empirical, became the fundamental source of logical positivism, or logical empiricism. Bertrand Russell adopted it as his position, and A. J. Ayer was to accept and profess it 15 years later. From the end of World War I until 1926, Wittgenstein was a schoolteacher in Austria. In 1929 his interest in philosophy renewed, and he returned to Cambridge, where even G. E. Moore came under his spell. At Cambridge Wittgenstein began a new wave in philosophical analysis distinct from the Tractatus, which had inspired the rise of logical positivism. Whereas the earlier Wittgenstein had concentrated on the formal structures of logic and mathematics, the later Wittgenstein attended to the fluidities of ordinary language. His lectures, remarks, conversations, and letters made lasting imprints on the minds of his most brilliant students, who have long since initiated the unending process of publishing them. During his lifetime Wittgenstein himself never published another book after the Tractatus. However, he was explicit that the work disclosing the methods and topics of his later years be published. This work, Philosophical Investigations (1953), is esteemed to be his most mature expression of his philosophical method and thought.