Hilbert's finitist program was not created at the beginning of the twenties solely to counteract Brouwer's intuitionism, but rather emerged out of broad philosophical reflections on the foundations of mathematics and out of detailed logical work; that is evident from notes of lecture courses that were given by Hilbert and prepared in collaboration with Bernays during the period from 1917 to 1922. These notes reveal a dialectic progression from a critical logicism through a radical constructivism toward finitism; the (...) progression has to be seen against the background of the stunning presentation of mathematical logic in the lectures given during the winter term 1917/18. In this paper, I sketch the connection of Hilbert's considerations to issues in the foundations of mathematics during the second half of the 19th century, describe the work that laid the basis of modern mathematical logic, and analyze the first steps in the new subject of proof theory. A revision of the standard view of Hilbert's and Bernays's contributions to the foundational discussion in our century has long been overdue. It is almost scandalous that their carefully worked out notes have not been used yet to understand more accurately the evolution of modern logic in general and of Hilbert's Program in particular. One conclusion will be obvious: the dogmatic formalist Hilbert is a figment of historical (de)construction! Indeed, the study and analysis of these lectures reveal a depth of mathematical-logical achievement and of philosophical reflection that is remarkable. In the course of my presentation many questions are raised and many more can be explored; thus, I hope this paper will stimulate interest for new historical and systematic work. (shrink)

David Hilbert was one of the great mathematicians who expounded the centrality of their subject in human thought. In this collection of essays, Wilfried Sieg frames Hilbert's foundational work, from 1890 to 1939, in a comprehensive way and integrates it with modern proof theoretic investigations.

It is a remarkable fact that Hilbert's programmatic papers from the 1920s still shape, almost exclusively, the standard contemporary perspective of his views concerning (the foundations of) mathematics; even his own, quite different work on the foundations of geometry and arithmetic from the late 1890s is often understood from that vantage point. My essay pursues one main goal, namely, to contrast Hilbert's formal axiomatic method from the early 1920s with his existential axiomatic approach from the 1890s. Such a (...) contrast illuminates the circuitous beginnings of the finitist consistency program and connects the complex emergence of existential axiomatics with transformations in mathematics and philosophy during the 19th century; the sheer complexity and methodological difficulties of the latter development are partially reflected in the well known, but not well understood correspondence between Frege and Hilbert. Taking seriously the goal of formalizing mathematics in an effective logical framework leads also to contemporary tasks, not just historical and systematic insights; those are briefly described as “one direction” for fascinating work. (shrink)

On June 4, 1925, Hilbert delivered an address to the Westphalian Mathematical Society in Miinster; that was, as a quick calculation will convince you, almost exactly sixty years ago. The address was published in 1926 under the title Über dasUnendlicheand is perhaps Hilbert's most comprehensive presentation of his ideas concerning the finitist justification of classical mathematics and the role his proof theory was to play in it. But what has become of the ambitious program for securing all of (...) mathematics, once and for all? What of proof theory, the very subject Hilbert invented to carry out his program? The Hilbertian ambition reached out too far: in its original form, the program was refuted by Gödel's Incompleteness Theorems. And even allowing more than finitist means in metamathematics, the Hilbertian expectations for proof theory have not been realized: a constructive consistency proof for second-order arithmetic is still out of reach. Nevertheless, remarkable progress has been made. Two separate, but complementary directions of research have led to surprising insights: classical analysis can be formally developed in conservative extensions of elementary number theory; relative consistency proofs can be given by constructive means for impredicative parts of second order arithmetic. The mathematical and metamathematical developments have been accompanied by sustained philosophical reflections on the foundations of mathematics. This indicates briefly the main themes of the contributions to the symposium; in my introductory remarks I want to give a very schematic perspective, that is partly historical and partly systematic. (shrink)

Wilfred Sieg and Mark Ravaglia. David Hilbert and Paul Bernays, Grundlagen der Mathematik I and II: A Landmark.

Die Logik, einst Grundbestand der Philosophie, hat sich in unserem J ahrhundert zu einer selbstandigen Wissenschaft ent 1 wickelt. Sie wird zur Abgrenzung gegeniiber friiheren Gestalten "neue Logik" oder "moderne Logik" genannt; auch sind Be zeichnungen wie "theoretische Logik", "mathematische Logik", "symbolische Logik", "formale Logik", "Logistik" gebrauch 2 lich, urn die Eigenart der grundlegenden Methoden anzudeuten. Die genannten Benennungen werden in dieser Arbeit gleichbe rechtigt gebraucht. Mit 1. M. BOCHENSKI und A. MENNE kann man unter Logistik in weiterem Sinne "die (...) Lehre vom Logikkalkiil, seinen Voraus 3 setzungen und Anwendungen" verstehen. Die Absicht dieser Arbeit ist eine philosophische; sie fragt nach dem, was die Aussage als Aussage zum Element positiver Logik werden laBt. In Frage ist daher die Aussagen- und (ele mentare) Pradikatenlogik, die in formaler Hinsicht "durch den Vollstandigkeitssatz (Go DEL I930) und den Unentscheidbarkeits- 1 Texte zur Geschichte der modernen Logik: I.M. BOCHENSKI, Formale Logik, Freiburg-Miinchen I956, S. 3II-477. 2 s. z.B.: B. JUH6s, Elemente der neuen Logik, Wien I954. G. HASEN]AEGER, Einfuhrung in die Grundbegritfe und Probleme der modernen Logik, Freiburg-Miinchen I962. D. HILBERT und W. ACKERMANN, Grundzi~ge der theoretischm Logik, 3. Aufl., B- lin-Gi:ittingen-Heidelberg I949. H. SCHOLZ und G. HASEN]AEGER, Grundzuge der mathematischen Logik, Berlin 1961. H. HERMES, Einfuhrung in die mathematische Logik, Stuttgart 1963. R. CARNAP, Symbolische Logik, Wien 1954. P. LORENZEN, Formale Logik. I.M. BOCHENSKI, GrundrifJ der Logistik, aus dem Franzi:isischen iibers., neubearb. und erweitert von A. MENNE, 2. erweiterte Auf I., Paderborn 1962. (shrink)

Two young logicians, whose work had a dramatic impact on the direction of logic, exchanged two letters in early 1931. Jacques Herbrand initiated the correspondence on 7 April and Kurt Gödel responded on 25 July, just two days before Herbrand died in a mountaineering accident at La Bérarde (Isère). Herbrand's letter played a significant role in the development of computability theory. Gödel asserted in his 1934 Princeton Lectures and on later occasions that it suggested to him a crucial part of (...) the definition of a general recursive function. Understanding this role in detail is of great interest as the notion is absolutely central. The full text of the letter had not been available until recently, and its content (as reported by Gödel) was not in accord with Herbrand's contemporaneous published work. Together, the letters reflect broader intellectual currents of the time: they are intimately linked to the discussion of the incompleteness theorems and their potential impact on Hilbert's Program. (shrink)

Religious sects and their practices have become highly topical in the recent past in Germany. The call for criminal sanctions in order to tackle actual or presumed misconduct is becoming louder and louder. The author, a criminal law professor, analyses the present discussion and puts it into a constitutional law perspective. Any civil society that aims to optimise the scope of the personal freedoms of its members must withstand the temptation of creating a special regime of criminal law rules just (...) to combat religious sects and their practices. Criminal law has tobe applied uniformly in the whole society. Therfore, criminal sanctions can only be handed out, when practices infringe intolerably with the individual' s rights protected by the law. (shrink)

Das Werk ist die erste komplett an allen Gebieten der Physik systematisch ausgerichtete Darstellung der Geschichte der Physik. Geschrieben von einem erfahrenen Didaktiker seines Faches und als Ergebnis jahrzehntelanger Recherche soll dieses Buch ein tieferes Verständnis seines Faches vermitteln, als dies traditionelle Lehrbücher vermögen. Der rote Faden sind die Konzepte und Theoriebildungen, wie sie sich durch die Jahrhunderte nachzeichnen lassen. Das Ergebnis ist ein lebendig geschriebenes Fachbuch, das sich sowohl zum Lernen und Nachschlagen systematisch nutzen wie auch als packende Physikgeschichte (...) von der ersten bis letzten Seite spannend lesen lässt. (shrink)

The Hygiene Hypothesis has been recognized as an important cornerstone to explain the sudden increase in the prevalence of asthma and allergic diseases in modernized culture. The recent epidemic of allergic diseases is in contrast with the gradual implementation of Homo sapiens sapiens to the present-day forms of civilization. This civilization forms a gradual process with cumulative effects on the human immune system, which co-developed with parasitic and commensal Helminths. The clinical manifestation of this epidemic, however, became only visible in (...) the second half of the twentieth century. In order to explain these clinical effects in terms of the underlying IgE-mediated reactions to innocuous environmental antigens, the low biodiversity of antigens in the domestic environment plays a pivotal role. The skewing of antigen exposure as a cumulative effect of reducing biodiversity in the immediate human environment as well as in changing food habits, provides a sufficient and parsimonious explanation for the rise in allergic diseases in a highly developed and helminth-free modernized culture. Socio-economic tendencies that incline towards a further reduction of environmental biodiversity may provide serious concern for future health. This article explains that the “Hygiene Hypothesis”, the “Old Friends Hypothesis”, and the “Skewed Antigen Exposure Hypothesis” are required to more fully explain the rise of allergy in modern societies. (shrink)

In Hume’s Of Miracles the person movecl by faith is put in a dilemma between faith and reason. Can one resolve this dilemma as a compleat Humean? The answer is yes. Within the Humean context different approaches can be developed ta overcome Hume’s dilemma. One uses Hume’s theory of utility to defend the belief in the afterlife. The other requires Hume to place faith on a par with beauty and therefore among the passions to which reason must be a slave. (...) Historically there was at least one compleat Humean who was also moved by faith --- Johann Georg Hamann [1730- 1788]. (shrink)

In this article we give a unifying approach to the theory of fundamental sequences and their related Hardy hierarchies of number-theoretic functions and we show the equivalence of the new approach with the classical one.

In his classic paper On Computable Numbers Turing analyzed what can be done by a human computor in a routine, “mechanical” way. He argued that mechanical op-erations obey locality conditions and are carried out on configurations satisfying boundedness conditions. Processes meeting these restrictive conditions can be shown to be computable by a Turing machine. Turing viewed memory limitations of computors as the ultimate reason for the restrictive conditions. In contrast, Gandy analyzed in his paper Church’s Thesis and Principles for Mechanisms (...) what can be done by “discrete deterministic mechanical devices” and appealed to physical considerations to motivate restrictive principles. These devices include, crucially, ones that carry out parallel processes, e.g., cellular automata. Following Turing’s methodological ways and guided by Conway’s “Game of Life” as a paradigm, Gandy formulated four restrictive principles and proved that devices satisfying them are computationally equivalent to Turing machines. (shrink)

Since their inception, the Perspectives in Logic and Lecture Notes in Logic series have published seminal works by leading logicians. Many of the original books in the series have been unavailable for years, but they are now in print once again. This volume, the fifteenth publication in the Lecture Notes in Logic series, collects papers presented at the symposium 'Reflections on the Foundations of Mathematics' held in celebration of Solomon Feferman's 70th birthday (The 'Feferfest') at Stanford University, California in 1988. (...) Feferman has shaped the field of foundational research for nearly half a century. These papers reflect his broad interests as well as his approach to foundational research, which emphasizes the solution of mathematical and philosophical problems. There are four sections, covering proof theoretic analysis, logic and computation, applicative and self-applicative theories, and philosophy of modern mathematical and logic thought. (shrink)

Die digitale Transformation erfasst die Medien der Literatur und Literaturkritik in unterschiedlicher Geschwindigkeit. Die Substituierung der gedruckten Zeitung, der Stammheimat der Literaturkritik, durch digitale Formate ist weit vorangeschritten. Auf dem Buchmarkt ist das gedruckte Hardcover nach wie vor ein relativ stabiles Element. Der Beitrag kommentiert diese Differenz in medienhistorischer Perspektive.

In this rapid commentary, a mini-review is given of the present state-of-knowledge regarding the etiology and epidemiology of the new coronavirus 2019-nCoV and the risks for developing Acute respiratory distress syndrome. The available knowledge on the viral genomics, molecular biology and pathogenicity of viruses of the Coronaviridae family and other Nidovirales, forms a helpful template for understanding the present pandemic outbreak. However, important questions remain unanswered about the underlying mechanism causing the very high case fatality ratios and mechanisms regarding severe (...) reactions like ARDS, fatal cardiac and renal failures, associated with a number of important comorbidity factors. Immunological reactions to lung alveoles in particular in late phase ARDS in SARS-like CoV diseases, so far may not have received enough attention. Finally a shortlist of questions for high priority further research is suggested. (shrink)

"Die Kritik ist nicht die Wissenschaft." Zu diesem Ergebnis führt eine Besinnung auf den Begriff der Objektivität in der kunstwissenschaftlichen Forschung. Die aktuelle Situation, die durch wissenschaftstheoretische und methodologische Überlegungen bestimmt ist, verlangt neue Zielsetzungen und Aufgaben. Das zentrale Problem - die Begründung der Ästhetik als selbständige, moderne Wissenschaft - steht und fällt mit der Frage, ob die Kunst Gegenstand einer generellen, empirisch prüfbaren Theorie sein kann. Der zeitgenössische Strukturalismus glaubt diese Frage positiv beantworten zu können. Er versucht, die ästhetischen (...) Gebilde nicht nur als registrierbare Einzelfälle zu erklären und zu bewerten, sondern auf allgemeinere Gesetzmäßigkeiten zurückzuführen. (shrink)

Using the concept of notations for infinitary derivations we give an explanation of Takeuti's reduction steps on finite derivations (used in his consistency proof for Π1 1-CA) in terms of the more perspicious infinitary approach from [BS88].

Plus que tout autre philosophe antique, Plotin semble mettre ses interprètes au défi de décrypter le fond de sa pensée. En effet, elle a l’air d’un système, mais le lecteur des Ennéades ne se voit pas livrer les structures conceptuelles principales qui doivent en assurer la cohérence. Emilsson s’est proposé le décryptage de certaines structures qui ont la fonction de principe conceptuel soit tout à fait général soit spécifique pour un champ thématique déterminé. Après avoir proposé une étude...