Polish logic logic as researched, elucidated, and taught in Poland, 1919–39. Between the two wars colleagues Jan Lukasiewicz, Tadeusz Kotarbigki, and Stanislaw Lesniewski, assisted by students-become-collaborators such as Alfred Tarski, Jerzy Slupecki, Stanislaw Jaskowski, and Boleslaw Sobocigski, together with mathematicians in Warsaw and philosophical colleagues elsewhere, like Kasimir Ajdukiewicz and Tadeusz Czezowski, made Warsaw an internationally known center of research in logic, metalogic, semantics, and foundations of mathematics. The Warsaw ‘school’ also dominated Polish philosophy, and made Poland the country that introduced modern logic even in secondary schools.
All three founders took their doctorates in Lvov under Kasimir Twardowski (1866–1938), mentor of leading thinkers of independent Poland between the wars. Arriving from Vienna to take the chair of philosophy at twenty-nine, Twardowski had to choose between concentrating on his own research and organizing the study of philosophy in Poland. Dedicating his life primarily to the community task, he became the founder of modern Polish philosophy.
Twardowski’s informal distinction between distributive and collective conceptions influenced classification of philosophy and the sciences, and anticipated Lesniewski’s formal axiomatizations in ontology and mereology, respectively. Another common inheritance important in Polish logic was Twardowski’s stress on the process–product ambiguity. He applied this distinction to disambiguate ‘meaning’ and refine his teacher Brentano’s account of mental acts as meaningful (‘intentional’) events, by differentiating (1) what is meant or ‘intended’ by the act, its objective noema or noematic ‘intentional object,’ from (2) its corresponding noetic meaning or subjective ‘content,’ the correlated characteristic or structure by which it ‘intends’ its ‘object’ or ‘objective’ – i.e., means that: suchand-such (is so). Twardowski’s teaching – especially this careful analysis of ‘contents’ and ‘objects’ of mental acts – contributed to Meinong’s theory of objects, and linked it, Husserl’s phenomenology, and Anton Marty’s ‘philosophical grammar’ with the ‘descriptive psychology’ of their common teacher, the Aristotelian and Scholastic empiricist Brentano, and thus with sources of the analytic movements in Vienna and Cambridge. Twardowski’s lectures on the philosophical logic of content and judgment prepared the ground for scientific semantics; his references to Boolean algebra opened the door to mathematical logic; and his phenomenological idea of a general theory of objects pointed toward Lesniewski’s ontology. Twardowski’s maieutic character, integrity, grounding in philosophical traditions, and arduous training (lectures began at six a.m.), together with his realist defense of the classical Aristotelian correspondence theory of truth against ‘irrationalism,’ dogmatism, skepticism, and psychologism, influenced his many pupils, who became leaders of Polish thought in diverse fields. But more influential than any doctrine was his rigorist ideal of philosophy as a strict scientific discipline of criticism and logical analysis, precise definition, and conceptual clarification. His was a school not of doctrine but of method. Maintaining this common methodological inheritance in their divergent ways, and encouraged to learn more mathematical logic than Twardowski himself knew, his students in logic were early influenced by Frege’s and Husserl’s critique of psychologism in logic, Husserl’s logical investigations, and the logical reconstruction of classical mathematics by Frege, Schröder, Whitehead, and Russell. As lecturer in Lvov from 1908 until his appointment to Warsaw in 1915, Lukasiewicz introduced mathematical logic into Poland. To Lesniewski, newly arrived from studies in Germany as an enthusiast for Marty’s philosophy of language, Lukasiewicz’s influential 1910 Critique of Aristotle’s principle of contradiction was a ‘revelation’ in 1911. Among other things it revealed paradoxes like Russell’s, which preoccupied him for the next eleven years as, logically refuting Twardowski’s Platonist theory of abstraction, he worked out his own solutions and, influenced also by Leon Chwistek, outgrew the influence of Hans Cornelius and Leon Petraźycki, and developed his own ‘constructively nominalist’ foundations.
In 1919 Kotarbisski and Lesniewski joined Lukasiewicz in Warsaw, where they attracted students like Tarski, Sobocigski, and Slupecki in the first generation, and Andrzej Mostowski and Czeslaw Lejewski in the next. When the war came, the survivors were scattered and the metalogicians Morchaj Wajsberg, Moritz Presburger, and Adolf Lindenbaum were killed or ‘disappeared’ by the Gestapo. Lukasiewicz concentrated increasingly on history of logic (especially in reconstructing the logic of Aristotle and the Stoics) and deductive problems concerning syllogistic and propositional logic. His idea of logical probability and development of three- or manyvalued and modal calculi reflected his indeterminist sympathies in prewar exchanges with Kotarbigski and Lesniewski on the status of truths (eternal, sempiternal, or both?), especially as concerns future contingencies. Lesniewski concentrated on developing his logical systems. He left elaboration of many of his seminal metalogical and semantic insights to Tarski, who, despite a divergent inclination to simplify metamathematical deductions by expedient postulation, shared with Lesniewski, Lukasiewicz, and Ajdukiewicz the conviction that only formalized languages can be made logically consistent subjects and instruments of rigorous scientific investigation. Kotarbigski drew on Lesniewski’s logic of predication to defend his ‘reism’ (as one possible application of Lesniewski’s ontology), to facilitate his ‘concretist’ program for translating abstractions into more concrete terms, and to rationalize his ‘imitationist’ account of mental acts or dispositions. Inheriting Twardowski’s role as cultural leader and educator, Kotarbigski popularized the logical achievements of his colleagues in (e.g.) his substantial 1929 treatise on the theory of knowledge, formal logic, and scientific methodology; this work became required reading for serious students and, together with the lucid textbooks by Lukasiewicz and Ajdukiewicz, raised the level of philosophical discussion in Poland. Jaskowski published a system of ‘natural deduction’ by the suppositional method practiced by Lesniewski since 1916. Ajdukiewicz based his syntax on Lesniewski’s logical grammar, and by his searching critiques influenced Kotarbigski’s ‘reist’ and ‘concretist’ formulations. Closest in Poland to the logical positivists of the Vienna Circle, Ajdukiewicz brought new sophistication to the philosophy of language and of science by his examination of the role of conventions and meaning postulates in scientific theory and language, distinguishing axiomatic, deductive, and empirical rules of meaning. His evolving and refined conventionalist analyses of theories, languages, ‘world perspectives,’ synonymy, translation, and analyticity, and his philosophical clarification by paraphrase anticipated views of Carnap, Feigl, and Quine. But the Polish thinkers, beyond their common methodological inheritance and general adherence to extensional logic, subscribed to little common doctrine, and in their exchanges with the Vienna positivists remained ‘too sober’ (said Lukasiewicz) to join in sweeping antimetaphysical manifestos. Like Twardowski, they were critics of traditional formulations, who sought not to proscribe but to reform metaphysics, by reformulating issues clearly enough to advance understanding. Indeed, except for Chwistek, the mathematician Jan Slezygski, and the historians I. M. Bochegski, Z. A. Jordan, and Jan Salamucha, in addition to the phenomenologist Roman Ingarden, the key figures in Polish logic were all philosophical descendants of Twardowski. See also KOTARBI gSKI, LESSNIEWSKI , LUKASIEWIC. E.C.L.