Edited by a leading exponent of the school, this book offers - in the words of the movement's founders - logical positivism's revolutionary theories on meaning and metaphysics, the nature of logic and mathematics, the foundations of knowledge, the content of psychological propositions, ethics, sociology, and the nature of philosophy itself. Includes: Classic papers by Schlick, Carnap, Neurath, and Hahn - published for the first time in English. Bertrand Russell's exposition of his philosophy of logical atomism, which preceded logical positivism's development. A detailed introduction by Professor Ayer that explains the movement's main ideas and their impact on contemporary philosophy in Britain and the United States. The most complete bibliography on the subject ever published.