 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.Logical positivism grew from the discussions of a group called the "First Vienna Circle" which 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.