  Tarski’s semantic ideas converted most members of the LWS to scientific realism. Formerly, under the influence of conventionalism, instrumentalism concerning scientific theories had adherents (Ajdukiewicz, Łukasiewicz). A radical form of anti-realism was developed by Poznański and Wundheiler in the 1930s. They pointed out that verification in empirical science is cyclic and principally anti-fundamentalistic. In particular, it is not possible to identify any data without a reference to theories. Hence, truth in science cannot consist in a correspondence with facts.