This book is a compact, accessible treatment of the main ideas advanced by the positivists, including Schlick, Carnap, Ayer, and the early Wittgenstein. Oswald Hanfling discusses such ideas as the 'verification principle' ('the meaning of this statement is the method of its verification') and the 'elimination of metaphysics, ' an attempt to show that metaphysical statements, for example about God, are unverifiable and therefore meaningless.