Stefania Centrone

Der Band versammelt neue Beiträge namhafter Husserl-Forscher und eröffnet analytische und phänomenologische Interpretationsperspektiven auf Husserls Werk. Zugleich versuchen die Autoren, die Diskussionsgrundlagen zwischen Husserl und einigen seiner wichtigsten und einflußreichsten Gesprächspartner wiederherzustellen: Bernard Bolzano, Franz Brentano, Gottlob Frege, Martin Heidegger und Ludwig Wittgenstein. Mit Beiträgen von: Christian Beyer, Stefania Centrone, Dagfinn Føllesdal, George Heffernan, Wolfgang Künne, Eduard Marbach und Markus Stepanians.

In his booklet "Contributions to a better founded presentation of mathematics" of 1810 Bernard Bolzano made his first serious attempt to explain the notion of a rigorous proof. Although the system of logic he employed at that stage is in various respects far below the level of the achievements in his later Wissenschaftslehre, there is a striking continuity between his earlier and later work as regards the methodological constraints on rigorous proofs. This paper tries to give a perspicuous and critical account of the fragmentary logic of Beyträge, and it shows that there is a tension between that logic and Bolzano's methodological ban on?kind crossing?

It is well known that Husserl, together with Plato and Leibniz, counted among Gödel’s favorite philosophers and was, in fact, an important source and reference point for the elaboration of Gödel’s own philosophical thought. Among the scholars who emphasized this connection we find, as Richard Tieszen reminds us, Gian-Carlo Rota, George Kreisel, Charles Parsons, Heinz Pagels and, especially, Hao Wang. Right at the beginning of After Gödel we read: “The logician who conducted and recorded the most extensive philosophical discussions with Kurt Gödel during Gödel’s later years was Hao Wang”.This book takes Wang’s report about Gödel’s philosophical interests seriously and paves the way “to go beyond the contributions of Plato, Leibniz and Husserl, based on Gödel’s philosophical and technical writings, his comments to Hao Wang, and various items from the Gödel Nachlass”. Tieszen proposes a “type of Gödelian platonic rationalism” about mathematic and logic that makes no pretenc..

This paper analyzes Mally’s system of deontic logic, introduced in his The Basic Laws of Ought: Elements of the Logic of Willing (1926). We discuss Mally’s text against the background of some contributions in the literature which show that Mally’s axiomatic system for deontic logic is flawed, in so far as it derives, for an arbitrary A, the theorem “A ought to be the case if and only if A is the case”, which represents a collapse of obligation. We then try to sort out and understand which axioms are responsible for the collapse and consider two ways of amending Mally’s system: (i) by changing its original underlying logical basis, that is classical logic, and (ii) by modifying Mally’s axioms.

Two centuries ago Bernard Bolzano published his Contributions to a more well-founded presentation of mathematics which Goethe praised as “an opusculum of very high value”. Bolzano still seems to accept the traditional principle that that intension and extension of a concept stand in an inverse relation. In particular he claims that the concept of a genus proximum is always a component of the concept of the species which are subordinated to it. However, this does not harmonize with his simultaneous assumption that there are simple species-concepts. In section 1 of this paper I shall try to bring to light this tension in Bolzanos Contributions. In section 2 I shall try to reconstruct Bolzano ’s arguments to the effect that the properties an object must have if it is to fall under a certain concept are not always components of that concept. In section 3 I shall try to reconstructs his arguments against the Canon in his Theory of Science.In seinen vor zwei Jahrhunderten erschienenen Beyträgen zu einer begründeteren Darstellung der Mathematik, die Goethe als „ein Werkchen von besonderem Werte“ pries, scheint Bernard Bolzano den traditionellen Lehrsatz der Reziprozität noch zu akzeptieren, demzufolge Inhalt und Umfang eines Begriffs in inversem Verhältnis stehen. Insbesondere akzeptiert er die traditionelle These, dass der Begriff eines genus proximum immer ein Bestandteil der Begriffe der Spezies dieses Genus ist. Diese Annahme schient aber im Gegensatz zu seiner gleichzeitigen Akzeptanz der These zu stehen, dass es einfache Spezies-Begriffe gibt. Im Paragraphen 1 bespreche ich diese Frage. Im Paragraphen 2 versuche ich, einige der Argumente zu rekonstruieren, die Bolzano in seiner Wissenschaftslehre zur Widerlegung der These verwendet, dass die Begriffe der Beschaffenheiten, die ein Gegenstand haben muss, um unter einen bestimmten Begriff zu fallen, immer Teile dieses Begriffs sind. Im Paragraphen 3 präsentiere ich die wichtigsten Argumente Bolzanos, die in der Wissenschaftslehre dafür verwendet werden, um den Kanon Allgemeingültigkeit abzusprechen.

Essays on Husserl’s Logic and Philosophy of Mathematics sets out to fill up a lacuna in the present research on Husserl by presenting a precise account of Husserl’s work in the field of logic, of the philosophy of logic and of the philosophy of mathematics. The aim is to provide an in-depth reconstruction and analysis of the discussion between Husserl and his most important interlocutors, and to clarify pivotal ideas of Husserl’s by considering their reception and elaboration by some of his disciples and followers, such as Oskar Becker and Jacob Klein, as well as their influence on some of the most significant logicians and mathematicians of the past century, such as Luitzen E. J. Brouwer, Rudolf Carnap, Kurt Gödel and Hermann Weyl. Most of the papers consider Husserl and another scholar – e.g. Leibniz, Kant, Bolzano, Brentano, Cantor, Frege – and trace out and contextualize lines of influence, points of contact, and points of disagreement. Each essay is written by an expert of the field, and the volume includes contributions both from the analytical tradition and from the phenomenological one.

By “mathesis universalis” Descartes and Leibniz understood a most general science built on the model of mathematics. Though the term, along with that of “mathesis universa”, had already been used during the seventeenth century, it was with Descartes and Leibniz that it became customary to designate it as a universal mathematical science that unifies all formal a priori sciences. In his Dissertatio de arte combinatoria (1666), early Leibniz writes that the mathesis is not a discipline, but unifies parts from different disciplines that have quantity as their subject. A while later, in a fragment entitled Elementa Nova Matheseos Universalis (1683?) he writes “the mathesis […] shall deliver the method through which things that are conceivable can be exactly determined”; in another fragment he takes the mathesis to be “the science of all things that are conceivable.” The more mature Leibniz considers all mathematical disciplines as branches of the mathesis and designs the mathesis as a general science of forms applicable not only to magnitudes but to every object that exists in our imagination, i.e. that is possible at least in principle. As a general science of forms the mathesis investigates possible relations between “arbitrary objects” (“objets quelconques”). It is an abstract theory of combinations and relations among objects whatever.

This explorative article is organized around a set of questions concerning the concept of a function. First, a summary of certain general facts about functions that are a common coin in contemporary logic is given. Then Frege's attempt at clarifying the nature of functions in his famous paper Function and Concept and in his Grundgesetze is discussed along with some questions which Freges' approach gave rise to in the literature. Finally, some characteristic uses of functional notions to be found in the work of Bernard Bolzano and in Edmund Husserl's early work are presented and elucidated.

In his earlyContributions to a Better-Grounded Presentation of Mathematics Bernard Bolzano tries to characterizerigorous proofs.Rigorousis,prima facie, any proof that indicates the grounds for its conclusion. Bolzano lists a number of methodological constraints all rigorous proofs should comply with, and tests them systematically against a specific collection of elementary inference schemata that, according to him, are evidently of ground-consequence-kind. This paper intends to give a detailed and critical account of the fragmentary logic of theContributions, and to point out as well some difficulties Bolzano’s attempt runs into, notably as to his methodological ban on ‘kind crossing’.

This paper analyzes and evaluates Bolzano's remarks on the apagogic method of proof with reference to his juvenile booklet "Contributions to a better founded presentation of mathematics" of 1810 and to his?Theory of science? (1837). I shall try to defend the following contentions: (1) Bolzanos vain attempt to transform all indirect proofs into direct proofs becomes comprehensible as soon as one recognizes the following facts: (1.1) his attitude towards indirect proofs with an affirmative conclusion differs from his stance to indirect proofs with a negative conclusion; (1.2) by Bolzano's lights arguments via consequentia mirabilis only seem to be indirect. (2) Bolzano does not deny that indirect proofs can be perfect certifications (Gewissmachungen) of their conclusion; what he denies is rather that they can provide grounds for their conclusions. (2.1) They cannot do the latter, since they start from false premises and (2.2) since they make an unnecessary detour. (3) The far-reaching agreement between his early and late assessment of apagogical proofs (in the Beyträge of 1810 and the Wissenschaftslehre of 1837) is partly due to the fact that he develops his own position always against the background of Wolff's and Lambert's views.

At a time when they had largely fallen into disrepute Bolzano reactivated the distinctions between ‚clear‘ and ‚obscure‘, ‚distinct‘ and ‚confused‘ ideas. In the central sections of this paper I offer a critical reconstruction of the explanations of these pairs of opposita which are to be found in vol. III of Bolzano's monumental Wissenschaftslehre. I then provide a detailed account of its Leibnizian counterparts that were well-known to the ‚Bohemian Leibniz‘, and finally I evaluate Bolzano's criticism thereof.

Two hundred years ago Bernard Bolzano published a booklet on the philosophy of mathematics that is the first major step forward in this area since Pascal’s De l’esprit géométrique. Following Aristotelian lines Bolzano distinguishes in his opusculum two kinds of proofs, those that simply show that something is the case, and those that explain why something is the case. In his Wissenschaftslehre this contrast reappears as that between derivability and consecutivity. Husserl takes up some of Bolzano’s key concepts in his Prolegomena to Pure Logic. In this paper I discuss, among other things, the question whether consecutivity can be regarded as a special case of derivability, as Husserl seems to think, and I contrast Bolzano’s rejection of any appeal to self-evidence with Husserl’s reliance on this notion.Genau vor zweihundert Jahren erschienen Bernard Bolzano Beyträge zu einer begründeteren Darstellung der Mathematik. Dieses Büchlein ist der erste Meilenstein in der Geschichte der Philosophie der Mathematik seit Pascals De l’esprit géométrique. Im Anschluss an Aristoteles unterscheidet Bolzano in seinem Opusculum zwei Arten von Beweisen: solche, die nur dartun, dass etwas der Fall ist, und solche, die erklären warum etwas der Fall ist. Im seiner Wissenschaftslehre erscheint dieser Kontrast als der zwischen Ableitbarkeit und Abfolge. Husserl übernimmt einige von Bolzanos Grundbegriffen in seinen Prolegomena zur reinen Logik. In diesem Aufsatz diskutiere ich u.a. die Frage, ob Abfolge ein Spezialfall von Ableitbarkeit ist, wie Husserl anzunehmen scheint, und ich kontrastiere Bolzanos Ablehnung jeder Berufung auf Evidenz mit Husserls Einstellung.