The philosophical atmosphere of a city or a country is a rather elusive sociological phenomenon. The opinions professed in universities are by no means all-decisive. Historical factors contribute to the atmosphere; for works from the past are discussed more widely and with greater understanding in the place of their origin, where disciples and disciples of disciples of the creators may still be active. Philosophical societies play a role. Informal conversations between intellectuals when they talk about philosophy (which they did abundantly in the Central Europe of the 1920's) contribute to the climate; and what students say is of some interest. The diverse nature of these elements makes it hard to avoid some desultoriness in the description of the atmosphere. Yet by following the development of all those factors in Vienna one may understand why the Schlick-Kreis blossomed just there.