Online research in philosophy

The aim of the present study is (1) to show, on the basis of a number of unpublished documents, how Heinrich Scholz supported his Warsaw colleague Jan ?ukasiewicz, the Polish logician, during World War II, and (2) to discuss the efforts he made in order to enable Jan ?ukasiewicz and his wife Regina to move from Warsaw to Münster under life-threatening circumstances. In the first section, we explain how Scholz provided financial help to ?ukasiewicz, and we also adduce evidence of (...) the risks incurred by German scholars who offered assistance to their Polish colleagues. In the second section, we discuss the dramatic circumstances surrounding the ?ukasiewiczes' move to Münster in the summer of 1944. (shrink)

We compare Jan ?ukasiewicz's and Karl Popper's views on induction. The English translation of the two ?ukasiewicz's papers is included in the Appendix.

The brief article of 1910 which is translated here is, as the prefatory note explains, significant for understanding both the way in which ?ukasiewicz came to many-valued logic and the influences under which he stood at the time.

Compulsion and Surprise Two phenomena conspire to convince people that the physical world exists independently of them. One is its recalcitrance, or insusceptibility to control. It resists and constrains our actions. Much as we might wish to do so, we cannot lift heavy boulders, walk through walls, jump rivers, breathe under water, or fly (unaided) over mountains. The other feature, which is connected to the first, is the world’s propensity to surprise us. The sights and sound, pressures and pains of (...) the world force themselves upon us in perception whether we want them to or not, and are often unexpected and surprising. An unusual bird appears in the garden, a stranger calls at the door and reveals he is a long-lost cousin, the post brings an invitation out of the blue, the car won’t start (surprises may be unpleasant as well as pleasant). These two phenomena, recalcitrance and surprise, form a large part of the platonist’s case for the existence of an independent mathematical reality. The recalcitrance of mathematical reality indeed appears to be stronger than that of the physical: the necessity with which mathematical results follow from assumptions is stricter than the physical necessity by which a wall resists attempts to walk through it. This has rarely been put more eloquently than by Jan Łukasiewicz. Speaking in particular of mathematical logic, he wrote.. (shrink)

The paper contains an attempt at formulating the project of logic comprised in Jan Łukasiewicz's article „On determinism” and a construction of a logic which would realise this project. Such a logic consists of three consequence-operations build upon a four-element algebra. The values of the algebra have been defined by means of the following set of sentences: true and true today, true but not true today, false but not false today and false and false today. It turns out that only (...) one of the consequences is different from the classical consequence and all of them are logically two-valued. It is proved moreover, that the assumption that tautologies consists of sentences-forms which are „always” true today, results in the non-existence of such tautologies. (shrink)

Jan Łukasiewicz distinguished three various formulations of the law of contradiction in Aristotle's considerations concerning axiomatic foundations of philosophia prima in the book Γ of Methaphysics. Łukasiewicz referred to these formulations as „ontological”, „logical”, and „psychological”, respectively. The author focuses his attention on the last of them, namely to the so called psychological approach. He finds this approach to be an inadequate interpretation of Aristotle's views and tries to show that the most appropriate interpretation is pragmatic-logical.

This paper presents two systems of natural deduction for the rejection of non-tautologies of classical propositional logic. The first system is sound and complete with respect to the body of all non-tautologies, the second system is sound and complete with respect to the body of all contradictions. The second system is a subsystem of the first. Starting with Jan Łukasiewicz's work, we describe the historical development of theories of rejection for classical propositional logic. Subsequently, we present the two systems of (...) natural deduction and prove them to be sound and complete. We conclude with a ‘Theorem of Inversion’. (shrink)

The life and work of Moj?esz Presburger (1904?1943?) are summarised in this article. Although his production in logic was small, it had considerable impact, both his own researches and his editions of lecture notes of Adjukiewicz and ?ukasiewicz. In addition, the surviving records of his student time at Warsaw University provide information on a little-studied topic.

We construct a faithful interpretation of ukasiewicz's logic in product logic (both propositional and predicate). Using known facts it follows that the product predicate logic is not recursively axiomatizable.We prove a completeness theorem for product logic extended by a unary connective of Baaz [1]. We show that Gödel's logic is a sublogic of this extended product logic.

This paper examines how the work of Frege was known and received in Poland in the period 1910?1935 (with one exception concerning the later work of Suszko). The main thesis is that Frege's reception in Poland was perhaps faster and deeper than in other countries, except England, due to works of Russell and Jourdain. The works of ?ukasiewicz, Le?niewski and Cze?owski are described.