PREFACE.This book gives the content of three lectures delivered at the University of London in October, 1934. The first chapter has already been printed in Psyche (1934); and the present publication has been aided by a grant from the Publication Fund of the University of London, for which I desire to express my thanks.My endeavour in these pages is to explain the main features of the method of philosophising which we, the Vienna Circle, use, and, by using try to develop further. It is the method of the logical analysis of science, or more precisely, of the syntactical analysis of scientific language. Only the method itself is here directly dealt with; our special views, resulting from its use, appear rather in the form of examples (for instance our empiricist and anti-metaphysical position in the first chapter, our physicalist position in the last).The purpose of the book -- as of the lectures -- is to give a first impression of our method and of the direction of our questions and investigations to those who are not yet acquainted with them. Therefore the form of presentation aims more at general lucidity that at scientific precision. Formulations which are more exact and therefore more suitable as a basis for argument, may be found in my book Logische Syntax der Sprache.