This is a comprehensive biography of Ludwig Prandtl (1875-1953), the father of modern aerodynamics. His name is associated most famously with the boundary layer concept, but also with several other topics in 20th century fluid mechanics, particularly turbulence (Prandtl's mixing length). Among his disciples are pioneers of modern fluid mechanics such as Heinrich Blasius, Theodore von Kármán and Walter Tollmien. Furthermore, Prandtl founded the Aerodynamische Versuchsanstalt (AVA) and the Kaiser-Wilhelm-Institut für Strömungsforschung in Göttingen, both of them seeds for (...) the growth of fluid mechanics in Germany. Yet Prandtl was also a representative of aeronautical research - from Imperial Germany via the Weimar Republic to the "Third Reich". Although not a party member, he assumed the role of a goodwill ambassador for Nazi Germany. This objective treatment of his career will be of interest to all scientists and historians wanting to learn more about Prandtl's influence and the early development of fluid- and aerodynamics. (shrink)

It is widely accepted that there is a clear sense in which the first-order paraconsistent constructive logic with strong negation of Almukdad and Nelson, QN4, is more constructive than intuitionistic first-order logic, QInt. While QInt and QN4 both possess the disjunction property and the existence property as characteristics of constructiveness (or constructivity), QInt lacks certain features of constructiveness enjoyed by QN4, namely the constructible falsity property and the dual of the existence property. This paper deals with the constructiveness of the (...) contra-classical, connexive, paraconsistent, and contradictory non-trivial first-order logic QC, which is a connexive variant of QN4. It is shown that there is a sense in which QC is even more constructive than QN4. The argument focuses on a problem that is mirror-inverted to Raymond Smullyan’s drinker paradox, namely the invalidity of what will be called the drinker truism and its dual in QN4 (and QInt), and on a version of the Brouwer-Heyting-Kolmogorov interpretation of the logical operations that treats proofs and disproofs on a par. The validity of the drinker truism and its dual together with the greater constructiveness of QC in comparison to QN4 may serve as further motivation for the study of connexive logics and suggests that constructive logic is connexive and contradictory (the latter understood as being negation inconsistent). (shrink)

Over the past ten years, the community researching connexive logics is rapidly growing and a number of papers have been published. However, when it comes to the terminology used in connexive logic, it seems to be not without problems. In this introduction, we aim at making a contribution towards both unifying and reducing the terminology. We hope that this can help making it easier to survey and access the field from outside the community of connexive logicians. Along the way, we (...) will make clear the context to which the papers in this special issue on Frontiers of Connexive Logic belong and contribute. (shrink)

In a recent article, Mario Günther presented a conditional that is claimed to be connexive. The aim of this short discussion note is to show that Günther’s claim is not without problems.

The knowability paradox is an instance of a remarkable reasoning pattern (actually, a pair of such patterns), in the course of which an occurrence of the possibility operator, the diamond, disappears. In the present paper, it is pointed out how the unwanted disappearance of the diamond may be escaped. The emphasis is not laid on a discussion of the contentious premise of the knowability paradox, namely that all truths are possibly known, but on how from this assumption the conclusion is (...) derived that all truths are, in fact, known. Nevertheless, the solution offered is in the spirit of the constructivist attitude usually maintained by defenders of the anti-realist premise. In order to avoid the paradoxical reasoning, a paraconsistent constructive relevant modal epistemic logic with strong negation is defined semantically. The system is axiomatized and shown to be complete. (shrink)

The topic of identity of proofs was put on the agenda of general (or structural) proof theory at an early stage. The relevant question is: When are the differences between two distinct proofs (understood as linguistic entities, proof figures) of one and the same formula so inessential that it is justified to identify the two proofs? The paper addresses another question: When are the differences between two distinct formulas so inessential that these formulas admit of identical proofs? The question appears (...) to be especially natural if the idea of working with more than one kind of derivations is taken seriously. If a distinction is drawn between proofs and disproofs (or refutations) as primitive entities, it is quite conceivable that a proof of one formula amounts to a disproof of another formula, and vice versa. A notion of inherited identity of derivations is introduced for derivations in a cut-free sequent system for Almukdad and Nelson’s constructive paraconsistent logic N4 with strong negation. The notion is obtained by identifying sequent rules the application of which has no effect on the identity of derivations. Then the notion of inherited identity is used to define a bilateralist notion of synonymy between formulas, which is a relation drawing more fine-grained distinctions between formulas than strong equivalence. (shrink)

In this paper, first some propositional conditional logics based on Belnap and Dunn’s useful four-valued logic of first-degree entailment are introduced semantically, which are then turned into systems of weakly and unrestrictedly connexive conditional logic. The general frame semantics for these logics makes use of a set of allowable (or admissible) extension/antiextension pairs. Next, sound and complete tableau calculi for these logics are presented. Moreover, an expansion of the basic conditional connexive logics by a constructive implication is considered, which gives (...) an opportunity to discuss recent related work, motivated by the combination of indicative and counterfactual conditionals. Tableau calculi for the basic constructive connexive conditional logics are defined and shown to be sound and complete with respect to their semantics. This semantics has to ensure a persistence property with respect to the preorder that is used to interpret the constructive implication. (shrink)

In this paper it is suggested to generalize our understanding of general (structural) proof theory and to consider it as a general theory of two kinds of derivations, namely proofs and dual proofs. The proposal is substantiated by (i) considerations on assertion, denial, and bi-lateralism, (ii) remarks on compositionality in proof-theoretic semantics, and (iii) comments on falsification and co-implication. The main formal result of the paper is a normal form theorem for the natural deduction proof system N2Int of the bi-intuitionistic (...) logic 2Int. The proof makes use of the faithful embedding of 2Int into intuitionistic logic with respect to validity and shows that conversions of dual proofs can be sidestepped. (shrink)

Professor Wilhelm Blasius, physiologist at Giessen in West Germany, has written a book "Probleme der Lebensforschung" (Verlag Rombach, Freiburg 1973) which - I understand - is to be published in an English version. To me it has been of interest as an orientation in a world of traditional German thinking, best known from Goethe's natural philosophy of perceptible "Ur­ bilder", which perhaps in English could be rendered descriptively by calling it an inner vision of further irre­ ducible totalities. It (...) is in contemporary language a kind of intuitive 'holistic' insight which represents understanding different from that of natural science. The latter is devoted to the study of causal chains, is largely experimental and in its aim ultimately 'reduc­ tionist' -to use another modern term. Goethe's approach is reincarnated in the "Wesenslehre" of the late Ludwig Klages (1872-1956) and in the thinking of Carl Gustav Caruso To Klages the perceived image alone is the meaning of everything in this world and in this sense he is the advocate of a psychological phenom­ enology that is an end in itself. Originally trained as a chemist Klages soon turned to philosophy and de­ veloped a system of concepts supposed to give a deeper insight into the essence of life than did the endless causal chains of natural science. Blasius makes much use of the concepts of this philosopher, in particular his ideas on 'polarities'. (shrink)

Proof Theory of Modal Logic is devoted to a thorough study of proof systems for modal logics, that is, logics of necessity, possibility, knowledge, belief, time, computations etc. It contains many new technical results and presentations of novel proof procedures. The volume is of immense importance for the interdisciplinary fields of logic, knowledge representation, and automated deduction.

This volume is dedicated to Prof. Dag Prawitz and his outstanding contributions to philosophical and mathematical logic. Prawitz's eminent contributions to structural proof theory, or general proof theory, as he calls it, and inference-based meaning theories have been extremely influential in the development of modern proof theory and anti-realistic semantics. In particular, Prawitz is the main author on natural deduction in addition to Gerhard Gentzen, who defined natural deduction in his PhD thesis published in 1934. The book opens with an (...) introductory paper that surveys Prawitz's numerous contributions to proof theory and proof-theoretic semantics and puts his work into a somewhat broader perspective, both historically and systematically. Chapters include either in-depth studies of certain aspects of Dag Prawitz's work or address open research problems that are concerned with core issues in structural proof theory and range from philosophical essays to papers of a mathematical nature. Investigations into the necessity of thought and the theory of grounds and computational justifications as well as an examination of Prawitz's conception of the validity of inferences in the light of three “dogmas of proof-theoretic semantics” are included. More formal papers deal with the constructive behaviour of fragments of classical logic and fragments of the modal logic S4 among other topics. In addition, there are chapters about inversion principles, normalization of proofs, and the notion of proof-theoretic harmony and other areas of a more mathematical persuasion. Dag Prawitz also writes a chapter in which he explains his current views on the epistemic dimension of proofs and addresses the question why some inferences succeed in conferring evidence on their conclusions when applied to premises for which one already possesses evidence. (shrink)

This conflict can be interpreted in both religious and nonreligious ways. However, some intellectuals have identified a common thread parallel to the theological axis. The research study determines the role of existential philosophy in the contemporary religious beliefs. They have interpreted this contradiction as the conflict between our current selves and aspirations. Recognizing our animality and the role that such creatures play in the world is a requirement of our rational side. You may guarantee a well-attended eulogy by eating well, (...) exercising, not being a burden, helping out where you can, raising the next generation, and leaving the area essentially as you found it when it's time to leave. We must deal with this since it is who we are and what we are at our core. However, to be human means to be unhappy with this chilly, conventional assessment. As human beings, we possess the capacity to make decisions that influence our potential. Our destiny is not predetermined and that we can use our willpower to slightly warm the universe's unbreakable laws so that we can bend and shape them into the things we want. In the end, the cosmos prevails, yet we try to become rather than just exist during our brief existence. In the ongoing struggle against finitude, we strive for transcendence. The general framework has secular and strong religious proponents, and this view has been widely referred to as existentialist. (shrink)

This study aims to investigate the influence of self-awareness on students’ ethical compliance, examine the impact of self-integrity on students’ ethical compliance, explore the effect of self-regulation on students’ ethical compliance, and analyze the influence of ethics education on students’ ethical compliance. Additionally, the research investigates whether ethics education taught in schools or universities has a greater impact compared to an individual’s personality on students’ ethical compliance. The population in this study comprises students in Indonesia. Data collection involves distributing questionnaires (...) through Google Forms, allowing one month for questionnaire completion. The study employs a significance level of 5% to examine the influence of independent variables on the dependent variable. The research findings demonstrate that self-awareness, self-integrity, self-regulation, and ethics education have significant influences on students’ ethical compliance. Furthermore, the study reveals that ethics education does not have a higher impact on students’ ethical compliance compared to the individual’s personality. Therefore, it is crucial to ensure that students possess good self-awareness, high levels of self-integrity, and self-regulation, and understand the ethics education they receive, as this will help enhance students’ ethics compliance. (shrink)

Excerpt from Die Religionsphilosophie des als-Ob: Eine Nachprufung Kants und des Idealistischen Positivismus Der theologischen Fakultat der Berliner Universitat uberreiche ich diese Blatter als Ausdruck des ehrerbietigsten Dankes fur die mir am 15. Dezember 1917 verliehene theologische Doktorwurde. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst (...) repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works. (shrink)

The objective of this article is to show that Whitehead had a very important philosophy of education both on the formal level. The consistency found is well worth noting. I researched many of Whitehead's major works for his formal views and Lucian Price's Dialogues of Alfred North Whitehead. In my opinion Price's book is the best available for the purpose of getting Whitehead's candid informal view of education. The paper is divided into sections according to the particular subject matter. Since (...) Whitehead describes education as the study of life and all of its manifestations . It is appropriate to cover some of these areas: the purpose of education, the role of science and speculation, education and civilization, and both the process of education and process education are reviewed. Whitehead's philosophy of education is sweeping in scope. In his philosophy we find the importance of experience, imagination, speculation, generalization, factual knowledge, specialization, relevance, intuition, novelty, curiosity, theory, practice, pleasure, harmony, freedom, discipline, technical and liberal education and unification. He, in fact, unifies all these seemingly different areas into a coherent philosophy of education. (shrink)

An important and original new contribution to lesbian and gay studies, We Are Everywhere brings together the key primary sources relating to the politics of homosexuality. Presenting political, historical, legal, literary, and psychological documents which trace the evolution of the lesbian and gay movement, it includes documents as diverse as organization pamphlets, essays, polemics, speeches, newspaper and journal articles, and academic papers. We Are Everywhere includes writings from the beginnings of the gay and lesbian movement in the 19th century by (...) Karl Ulrichs, Magnus Hirschfeld, and John Addington Symonds; legal and government studies concerning rights of gay and lesbian citizens; articles from the early US liberation movement publications such as Mattachine Review , The Ladder and ONE ; documents from the first days of the AIDS epidemic to current activism; statements and writings from the movements within "the movement" (bisexuals, S/M, conservatives); and finally, a look at the future of lesbian and gay politics. Together the documents allow readers to examine a diverse set of issues: the concept of gay love before "homosexuality," the development of political movements based on homosexual identity, the history of government persecution of homosexuality, the impact of feminism on the modern lesbian and gay rights movement, and the emergence of queer theory. (shrink)

References to God. Some Remarks by Wittgenstein on Religion in the Years 1949 – 51. After a brief overview of Wittgenstein's stock of remarks on the subject of religion from 1949 – 1951, this article will focus on two particular points: (1) supposedly nonsensical conceptions of God, for instance in the context of proofs of God, (2) definitions of the term ”God” by hinting at something. Connections between (1) and (2) both systematically and exegetically within the framework of Wittgenstein's remarks (...) are made. Ich danke Anja Weiberg für sehr hilfreiche Kommentare. (shrink)

Ein Buch nicht der Re-Mythisierung, sondern der Mythoskritik, allerdings einer Kritik, die den Mythos ernst nimmt. Daher: »Mein Thema lautet: die Funktion der Genealogie im Mythos. So formuliert, setzt es eine rationale Vorstellung vom Funktionieren des Mythos voraus – es fordert zu einer systematischen Erörtertung auf. Wir brauchen nicht zu befürchten, daß eine systematische Erörterung das Mystische des Mythos verfehlt, weil sie archaische Verhältnisse dem Zwang der Rationalität unterwirft. Eher wird sie die Verbindung deutlich machen, die zwischen Mythos, Rationalität und (...) Zwang besteht.«. (shrink)

Bei Gilles Deleuze findet man einen der seltenen Ansätze zu einem genuin philosophischen Verständnis der Linie. Er versucht eine Emanzipation der Linie nicht nur aus der Geometrie, sondern auch aus der Dominanz des Raumes. Die wichtigsten Motive, die ihn dabei leiten, hat er in dem Konzept der Fluchtlinie gebündelt. Dessen potentiell metaphorischer Status wird ebenso befragt wie seine Aussagekraft für das deleuzianische Verständnis von Philosophie überhaupt. The work of Gilles Deleuze is one of the rare cases in which a genuinely (...) philosophical understanding of the line is attempted. He not only tries to dissociate the line from geometry, but also to free it from the dominance of space. The most important motives behind his thinking about the line converge in the concept of the ›ligne de fuite‹. The text examines the potentially metaphorical status of this notion, as well as its significance for Deleuze’s view of philosophy in general. (shrink)