 In his early philosophy, the most significant and influential position adopted by Łukasiewicz is his anti-psychologism in logic. This was influenced by Frege, Husserl and Russell. It manifested itself terminologically in Łukasiewicz’s replacement of the traditional term sąd (judgement), used by Twardowski, by the term zdanie (sentence). This change of perspective and terminology was adopted by subsequent Polish logicians en masse. After 1920, Łukasiewicz is very sparing in his statements regarding philosophy and philosophical problems. His abiding commitment to indeterminism we have noted. His main comments and indeed ire are reserved for those who criticise the place of mathematical logic (or logistic, as it was then known) in philosophy and thought in general. He noted certain convergences in method and style between the Lwów–Warsaw School and the Vienna Circle, but criticised the latter for their conventionalism and rejection of all metaphysics and for their attempt to turn substantive problems into linguistic ones. Despite its abstractness, logic is no more detached from reality than any other science, and it is constrained to conform to aspects of the world. It was his conviction that determinism was false that drove his rejection of bivalent logic. While maintaining the metaphysical neutrality of logic, he admitted later in the 1930s that whereas he had earlier been a nominalist, he was now a platonist. The source of this conviction is stated at the end of his 1937 polemic “In defence of logistic”: