Zuzana Rybaříková

This paper introduces Prior’s unpublished paper Aristotle on Logical Squares, which is deposited in the Bodleian Library and which discusses Greniewski’s definition of the \ operator, which Greniewski introduced in his paper Próba ‘odmłodzenia’ kwadratu logicznego. It is a unique attempt to formalize the square of opposition. Bendiek’s review, which is an important intermediary between Greniewski’s and Prior’s paper, is also mentioned here. Greniewski’s main motivation was to rejuvenate the traditional square of opposition in order to make a square of opposition more precise. He did not investigate the history of the square of opposition. Prior’s approach differs a great deal from Greniewski’s one because he bases his analyses of Greniewski’s operator on Aristotle’s definitions of squares of oppositions. There are some queries, which arise due to the different aims of Greniewski and Prior and their different approach might have caused Prior’s effort to the approximation of Greniewski’s operator to Aristotle’s definitions of the squares of opposition was unsuccessful.

This paper presents the link between Arthur N. Prior and logicians that belonged to the Lvov-Warsaw School. Although certain members of the Lvov-Warsaw School influenced Prior’s views, the amount and the form of the impact are still under discussion. Prior also cooperated with some of them in the development of his systems of logic. This paper focuses on four main areas in which Prior admitted adopting ideas from the Lvov-Warsaw School: systems of propositional logic, the history of logic, modal and temporal logic and ontology. Prior’s published works as well as his correspondence, which is stored in Prior’s Nachlass, are used to describe the influence.

In the nineteenth century, philosophy was at a crossroads. While the natural and technical sciences were developing in an unprecedented fashion, philosophy seemed to be stalled. Inspired by the progress of the natural sciences, many philosophers attempted to make such progress in philosophy and make philosophy a truly scientific discipline. This effort was also reflected in the philosophy of the Lvov-Warsaw school. While its founder, Kazimierz Twardowski, following his teacher Franz Brentano, promoted psychology as a method of scientific philosophy, one of his first students, Jan Łukasiewicz, was convinced that mathematical logic was such a method. To use mathematical logic as a tool, Łukasiewicz had to, however, argue convincingly that logic is an independent science and hence is not a part of psychology, i.e., arguing for anti-psychologism in logic. He initially adopted the arguments provided by Husserl, then celebrated as a proponent of anti-psychologism, and Frege’s views. When Łukasiewicz developed, however, his systems of many-valued logic, he denied almost all the principles that characterise Husserl and Frege’s anti-psychologism, i.e., the objectivity of the laws of logic, the existence of apodictic propositions, and the distinction between a priori and empirical sciences. He was, however, a proponent of anti-psychologism up to the end of his life. The aim of my paper is to introduce Łukasiewicz’s unique concept of anti-psychologism that significantly affected the views of mathematical logic in the Lvov-Warsaw School, and the views of his colleagues which helped him develop the concept.

In recent times there has been a shift in the interpretation of Aristotle’s logic. Many researchers have pointed out that the concept of existential import appears in Aristotle’s logic and philosophy, and that Aristotle worked with the concept of empty terms although his concept differs from that which is used in modern logic. Additionally, his search for the “culprits” of old and incorrect interpretation has been tied to the development of modern interpretation. Apart from the traditional concept of the logical square and syllogistics, where the assumption of non-emptiness of terms was widely used, J. L. Łukasiewicz is also labeled as an offender. This article tries to show that Łukasiewicz was aware that Aristotle was also dealing with empty terms. His restriction of syllogistics to only non-empty terms therefore differs significantly from the approach of traditional logicians.

Arthur Prior was one of the logicians who participated in the invention of the possible worlds’ semantics. The ontology, which is connected with his systems of modal logic, is unique. Prior tried to reduce the number of abstract entities as much as possible. Hence he did not elect to introduce possible worlds and possibilia into his ontology. In addition, he held a reductionist view, which is called modal actualism by Fine or modalism by Melia. Prior was inspired by various authors but this paper mainly discusses the influence of two prominent sources, Wittgenstein and logicians from Warsaw School. Prior acknowledged Wittgenstein’s influence, when he discuss the view that possible worlds consist of propositions. The second important feature of Prior’s concept is the denial of the real existence of possible worlds and the denial of the existence of entities which are in them. It was probably enabled by Prior’s adoption of some systems of logic invented by logicians from the Warsaw school, especially Lesniewski’s and Łukasiewicz’s systems.

Jan Łukasiewicz is known primarily as the founder of the three-valued system of logic. It is also generally renowned that his reason for introducing many-valued systems of logic was an attempt to refute determinism. When he developed the three-valued and n-valued logic, he employed these systems in his arguments against determinism. On the contrary, Łukasiewicz preferred the four-valued system of logic that is not suitable for a refutation of determinism in his latest period. It seems, however, that determinism still interested Łukasiewicz, as he discussed its denial in his last work, the second edition of the book Aristotle’s syllogistic from the standpoint of modern formal logic. The aim of my paper is to introduce the issue and describe the relation of these two topics primarily in the latest period of Łukasiewicz’s work. There are several possible solutions to the issue. However, Łukasiewicz never addressed the issue clearly in his published works. Therefore, the solutions might be supported or contradicted by his unpublished works in the future.

Although Łukasiewicz and Quine do not share many common views, they agreed on one important point in the 1950s: they both denied the distinction between empirical and a priori sciences. This agreement might be surprising as this denial was rather controversial at that time. This paper focuses on Quine’s and Łukasiewicz’s denials of the distinction between empirical and a priori sciences, and proposes three possible answers to the question of why both formulated the same conclusion at a similar time. Firstly, it discusses Quine’s possible influence on Łukasiewicz as Łukasiewicz agreed with Quine’s criticism of modality at that time. Secondly, it considers the possibility that Quine was affected by Łukasiewicz via his debates with Łukasiewicz’s student, Tarski. Lastly, it takes into account the possibility that both philosophers were inspired by an external source, namely the rise of quantum mechanics.

At the beginning of modern logic, propositions were defined as unchangeable entities placed in a certain idealistic realm. These unchangeable propositions contain in themselves so-called indexical, i.e. the place, time and other circumstances of the utterance. This concept of the proposition, which is entitled eternalism, was and is still prevalent among analytic philosophers. Often even the term ‘proposition’ is identified with an idealistic entity located outside the real world. In my paper, I would like to focus on the concept of propositions of two logicians who deviated from the standard understanding of propositions, Arthur N. Prior and Pavel Tichý. They were both proponents of temporalism, i.e. the view that propositions could change their truth-value over time. The paper will discuss the reasons why they were proponents of temporalism and compare their views. It claims that in Prior’s case, his metaphysical views were the main reasons he was a proponent of temporalism. In contrast, when Tichý presented his arguments for temporalism, he focused primarily on natural language.

Since Kazimierz Twardowski introduced the notions of “symbolomania” and “pragmatophobia,” the relationship between logic and reality was the focus of the philosophers from the Lvov-Warsaw School — inter alia two prominent logicians of the group, Stanisław Leśniewski and Jan Łukasiewicz. Bolesław Sobociński has pointed out, however, that there was a contrast between their approach to logic and reality. Despite being members of the same philosophical group and even colleagues from the same department, their philosophical views on the position of logic in reality differed considerably. Yet they both agreed that reality has a certain importance for logic and that logic could be valuable for reality. The aim of this paper is to introduce their divergent positions and describe in more detail how Leśniewski and Łukasiewicz understood the relationship between logic and the real world.

In his paper ‘The logic of temporal discourse’, Pavel Tichý pointed out that contemporary systems of logic were unable to sufficiently formalise tenses. He therefore suggested temporal specification in transparent intensional logic (TIL), a system of logic that he developed. Discussing contemporary systems of logic, Tichý also took into account the system of Arthur N. Prior, who developed the first systems of modern temporal logic, and his criticism was also addressed to Prior. Tichý only focused, however, on Prior’s early systems of temporal logic. Patrick Blackburn recently raised the awareness that Prior also developed systems of hybrid logic in his latest periods. From the point of view of temporal specification, this system is particularly interesting as the system has greater expressive power than Prior’s early systems of temporal logic. It could also consequently deal with the problematic specifications of tenses that Pavel Tichý pointed out. It is not only the formal criterion that make Tichý and Prior’s approach suitable for comparison. Both logicians shared similar views on time and logic. All these convictions also influenced their systems of logic. The aim of this paper is to demonstrate that the temporal propositions that Tichý introduced as problematic could be formalised in Prior’s hybrid temporal logic. I will also compare formalisations in TIL and hybrid logic and Tichý and Prior’s views that influenced their systems of logic.

Stanisław Leśniewski developed a system of logic and foundations of mathematics that considerably differs from Russell and Whitehead’s system. The difference between these two approaches to logic is significant primarily in the case of Leśniewski’s calculus of names, Ontology, and the concept of names that it contains. Russell’s theory of descriptions played a much more important role than Leśniewski’s concept of names in the history of philosophy. In response to that, several researchers aimed to approximate Leśniewski’s concept of names to Russell’s theory. There are several such attempts. This paper presents an interpretation that was suggested by Arthur Prior. Prior interpreted Leśniewskian names as class names. This interpretation was rejected by such prominent Leśniewskian scholars as Peter Simons or Rafal Urbaniak. According to Simons, class names oppose Leśniewski’s ontological views. Urbaniak claimed that Prior’s interpretation of Leśniewskian names as class names is unclear. The aim of this paper is to demonstrate that from the formal point of view, Prior’s interpretation could be justified.

AbstractŁukasiewicz introduced a new methodological approach to the history of logic. It consists of the use of modern formal logic in the research of the history of logic. Although he was not the first to use formal logic in his historical research, Łukasiewicz was the first who used it consistently and formulated it as a requirement for a historian of logic. The aim of this paper is to present Łukasiewicz's contribution and the history of its formulation. In addition, the paper will present its reception. There are two main themes in Łukasiewicz’s work on the history of logic. He discussed Stoic logic and Aristotle’s syllogistic. The second part of the paper focuses on current reception of Łukasiewicz’s contribution and on the question of whether there is a difference between knowledge about his contribution to Stoic logic and to Aristotle’s syllogistic, given that it has been hypothesised that Łukasiewicz’s contribution is currently more known among Aristotelian scholars than among those who focus on Stoic logic. Based on the papers that have appeared in the last five years at Web of Science and Scopus this hypothesis has not been confirmed.

J. M. E. McTaggart famously divided time into two time series, which he entitled A-series and B-series. Although he was proponent of neither of them, his division initiated a discussion as to which of the series is prior or real. This paper follows Clifford Williams’s claim that these series are not as distant as their proponents argue they are. It demonstrates their translatability in the case of examples from temporal logic and natural language. It argues that, if there are any deep-rooted differences between these two series, they are only metaphysical. These metaphysical differences could be overcome by focusing on logic or natural language. These two series of time are also used in computer science and in the development of Artificial Intelligence. However, no attempt at unifying them has been suggested in these fields of study. J. M. E. McTaggart rozdělil čas na dvě časové série, A-série a B-série. Třebaže nebyl zastáncem žádné z nich, jeho rozdělení podnítilo diskuzi, která z těchto časových sérií je přednější nebo jediná skutečně reálná. Tento článek navazuje na názor Clifforda Williamse, že tyto časové série nejsou tak rozdílné, jak tvrdí jejich zastánci. V článku je demonstrována jejich přeložitelnost na příkladech z temporální logiky a přirozeného jazyka. Článek dále tvrdí, že jestliže je zde nějaký hluboce zakořeněný rozdíl mezi těmito dvěma sériemi, pak je pouze metafyzický. Tyto metafyzické rozdíly mohou být překonány, zaměříme-li se na logiku a přirozený jazyk. Tyto dvě časové série jsou také použity v informatice a rozvoji umělé inteligence, třebaže v těchto oborech dosud nebyly navrženy žádné pokusy o jejich propojení.

Stanisław Leśniewski postuloval systém logiky a základu matematiky, jenž se do značné míry liší od systému, který navrhli Russell a Whitehead ve své knize Principia Mathematica. Velmi odlišný je zejména Leśniewského kalkul jmen a pojetí jmen, jež jsou jeho součástí. Russellova teorie deskripcí hrála v historii filozofie nesrovnatelně důležitější roli než Leśniewského teorie, proto se snažili někteří Leśniewského pokračovatelé přiblížit Leśniewského pojetí jmen Russellově teorii. Existuje hned několik takových návrhů, tento článek se ale zaměřuje pouze na interpretaci, kterou navrhl Arthur N. Prior. Prior interpretoval Leśniewského pojetí jmen jako třídová jména (class names). Tato interpretace je odmítána tak významnými badateli, jako je Peter Simons nebo Rafal Urbaniak. Podle Simonse neodpovídají třídová jména Leśniewského pojetí ontologie. Urbaniak o třídových jménech napsal, že Prior představil svou interpretaci nejasně. Cílem tohoto článku je ukázat, že pokud je na celý problém nahlíženo z formálního hlediska, může mít Priorovo pojetí opodstatnění.