Logical positivism & Vienna Circle

Logical positivism (later and more accurately called logical empiricism) is a school of philosophy that combines empiricism, the idea that observational evidence is indispensable for knowledge of the world, with a version of rationalism, the idea that our knowledge includes a component that is not derived from observation. It grew from the discussions of the so-called "First Vienna Circle" that gathered at the Café Central before World War I. After the war Hans Hahn, a member of that early group, helped bring Moritz Schlick to Vienna. Schlick's Vienna Circle, along with Hans Reichenbach's Berlin Circle, propagated the new doctrines more widely in the 1920s and early 1930s. It was Otto Neurath's propaganda that made the movement self-conscious and more widely known. A 1929 pamphlet written by Neurath, Hahn, and Rudolf Carnap summarized the doctrines of the Vienna Circle at that time. These included especially: the opposition to all metaphysics, especially ontology and synthetic a priori propositions; the rejection of metaphysics not as wrong but as having no meaning; a criterion of meaning based on Ludwig Wittgenstein's early work; the idea that all knowledge should be codifiable in a single standard language of science; and above all the project of "rational reconstruction", in which ordinary-language concepts were gradually to be replaced by more precise equivalents in that standard language. In the early 1930s, the movement dispersed, mainly because of political upheaval and the untimely deaths of Hahn and Schlick. During this period of upheaval, Carnap proposed a replacement for the earlier doctrines in his "Logical Syntax of Language". This change of direction and the somewhat differing views of Reichenbach and others led to a consensus that the English name for the shared doctrinal platform, in its American exile from the late 1930s, should be "logical empiricism".