After attending Eton and Oxford University, Sir Alfred Jules Ayer studied philosophy at the University of Vienna, where he affiliated with the Vienna Circle, the school of logical positivism led by Moritz Schlick. On his return to England, he accepted an appointment in 1933 as lecturer at Oxford, and, except for his military service during World War II, he wrote and taught philosophy until his death. During World War II, Ayer was commissioned into the Welsh Guards, and in 1945 was an attache at the British Embassy in Paris. In 1946 he was appointed Grote Professor at the University of London and in 1959 Wykeham Professor of Logic at Oxford. Ayer's fame was established with the publication of his first book, Language, Truth and Logic, in 1936. This work introduced logical positivism to the English-speaking world in a clear, vigorous, and persuasive style. Building on the thought of Bertrand Russell and Ludwig Wittgenstein, Ayer sharpened their theses, boldly revealing the affiliations of logical positivism with traditional British empiricism, particularly the work of David Hume. Ayer claimed that only verifiable statements are true or false. He considered statements of religion or art as merely emotional expressions. For his contributions to philosophy, Ayer was knighted by the British Crown. He has provided an account of his life, at least of its professional and philosophical sides, in two autobiographies.