This volume is meant to bring to a close the posthumous edition of the works of Husserl that date from the period prior to Logical Investigations. As such it complements volumes 12 and 22 of Husserliana. It is divided into two major parts; the first deals with arithmetical and the second with geometric issues.

Husserl left many unpublished drafts explaining (or trying to) his views on spatial representation and geometry, such as, particularly, those collected in the second part of Studien zur Arithmetik und Geometrie (Hua XXI), but no completely articulate work on the subject. In this paper, I put forward an interpretation of what those views might have been. Husserl, I claim, distinguished among different conceptions of space, the space of perception (constituted from sensorial data by intentionally motivated psychic functions), (...) that of physical geometry (or idealized perceptual space), the space of the mathematical science of physical nature (in which science, not only raw perception has a word) and the abstract spaces of mathematics (free creations of the mathematical mind), each of them with its peculiar geometrical structure. Perceptual space is proto-Euclidean and the space of physical geometry Euclidean, but mathematical physics, Husserl allowed, may find it convenient to represent physical space with a non-Euclidean structure. Mathematical spaces, on their turn, can be endowed, he thinks, with any geometry mathematicians may find interesting. Many other related questions are addressed here, in particular those concerning the a priori or a posteriori character of the many geometric features of perceptual space (bearing in mind that there are at least two different notions of a priori in Husserl, which we may call the conceptual and the transcendental a priori). I conclude with an overview of Weyl’s ideas on the matter, since his philosophical conceptions are often traceable back to his former master, Husserl. (shrink)

This article explores the changing relationships between geometric and arithmetic ideas in medieval Europe mathematics, as reflected via the propositions of Book II of Euclid’s Elements. Of particular interest is the way in which some medieval treatises organically incorporated into the body of arithmetic results that were formulated in Book II and originally conceived in a purely geometric context. Eventually, in the Campanus version of the Elements these results were reincorporated into the arithmetic books of the Euclidean treatise. Thus, while (...) most of the Latin versions of the Elements had duly preserved the purely geometric spirit of Euclid’s original, the specific text that played the most prominent role in the initial passage of the Elements from manuscript to print—i.e., Campanus’ version—followed a different approach. On the one hand, Book II itself continued to appear there as a purely geometric text. On the other hand, the first ten results of Book II could now be seen also as possiblytranslatable into arithmetic, and in many cases even as inseparably associated with their arithmetic representation. (shrink)

Husserl left many unpublished drafts explaining (or trying to) his views on spatial representation and geometry, such as, particularly, those collected in the second part of Studien zur Arithmetik und Geometrie (Hua XXI), but no completely articulate work on the subject. In this paper, I put forward an interpretation of what those views might have been. Husserl, I claim, distinguished among different conceptions of space, the space of perception (constituted from sensorial data by intentionally motivated psychic functions), (...) that of physical geometry (or idealized perceptual space), the space of the mathematical science of physical nature (in which science, not only raw perception has a word) and the abstract spaces of mathematics (free creations of the mathematical mind), each of them with its peculiar geometrical structure. Perceptual space is proto-Euclidean and the space of physical geometry Euclidean, but mathematical physics, Husserl allowed, may find it convenient to represent physical space with a non-Euclidean structure. Mathematical spaces, on their turn, can be endowed, he thinks, with any geometry mathematicians may find interesting. Many other related questions are addressed here, in particular those concerning the a priori or a posteriori character of the many geometric features of perceptual space (bearing in mind that there are at least two different notions of a priori in Husserl, which we may call the conceptual and the transcendental a priori). I conclude with an overview of Weyl’s ideas on the matter, since his philosophical conceptions are often traceable back to his former master, Husserl. (shrink)

Aus dem vielfältigen Werk von Hermann von Helmholtz versammelt diese Ausgabe die im engeren Sinne philosophischen Abhandlungen, vor allem zur Wissenschaftsphilosophie und Erkenntnistheorie, sowie Vorträge und Reden, bei denen der Autor seine Ausnahmestellung im Wissenschaftsbetrieb nutzte, um die Wissenschaften und ihre Institutionen in der bestehenden Form zu repräsentieren und zu begründen. Ein Philosoph wollte Helmholtz nicht sein, aber er legte der philosophischen Reflexion wissenschaftlicher Erkenntnis und wissenschaftlichen Handelns große Bedeutung bei. Vor allem bezog er, in der Regel ausgehend von seinen (...) fachwissenschaftlichen Forschungen, in den verschiedensten Kontexten zu erkenntnistheoretischen und methodologischen Problemen der Wissenschaften Stellung. Bereits »Ueber die Erhaltung der Kraft« (1847) lässt erkennen, wie verwoben naturwissenschaftliche Grundlagenforschung und philosophische Grundlagenreflexion in seinem Werk sind. Die aus den frühen sinnesphysiologischen Forschungen hervorgegangene empiristische Wahrnehmungslehre trug ihm den Ruf ein, ein maßgeblicher Vertreter des Neukantianismus zu sein. Spätere Arbeiten v.a. zur Geometrie und Arithmetik – das zeigt die vorliegende Ausgabe – stellen jedoch eine radikale Absage an den konstitutiven Kern des Kantianismus (nämlich die Existenz synthetischer Urteile a priori) dar. Helmholtz’ philosophische Beiträge sind bisher in ihrer Vollständigkeit nicht annähernd so gut zugänglich wie sein naturwissenschaftliches Werk. Die Ausgabe enthält außerdem bibliographische Vorberichte zur Einordnung, detaillierte Namens- und Sachregister sowie mit 575 Einträgen für den Zeitraum zwischen 1842 und 2012 die erste umfassende Bibliographie von Helmholtz verfasster Werke überhaupt. »Ich glaube, dass der Philosophie nur wieder aufzuhelfen ist, wenn sie sich mit Ernst und Eifer der Untersuchung der Erkenntnissprocesse und der wissenschaftlichen Methode zuwendet. Da hat sie eine wirkliche und berechtigte Aufgabe.« Helmholtz in einem Brief um 1875. (shrink)

This paper develops some respects in which the philosophy of mathematics can fruitfully be informed by mathematical practice, through examining Frege's Grundlagen in its historical setting. The first sections of the paper are devoted to elaborating some aspects of nineteenth century mathematics which informed Frege's early work. (These events are of considerable philosophical significance even apart from the connection with Frege.) In the middle sections, some minor themes of Grundlagen are developed: the relationship Frege envisions between arithmetic and geometry (...) and the way in which the study of reasoning is to illuminate this. In the final section, it is argued that the sorts of issues Frege attempted to address concerning the character of mathematical reasoning are still in need of a satisfying answer. (shrink)

Euclidean geometry, as presented by Euclid, consists of straightedge-and-compass constructions and rigorous reasoning about the results of those constructions. We show that Euclidean geometry can be developed using only intuitionistic logic. This involves finding “uniform” constructions where normally a case distinction is used. For example, in finding a perpendicular to line L through point p, one usually uses two different constructions, “erecting” a perpendicular when p is on L, and “dropping” a perpendicular when p is not on L, (...) but in constructive geometry, it must be done without a case distinction. Classically, the models of Euclidean geometry are planes over Euclidean fields. We prove a similar theorem for constructive Euclidean geometry, by showing how to define addition and multiplication without a case distinction about the sign of the arguments. With intuitionistic logic, there are two possible definitions of Euclidean fields, which turn out to correspond to different versions of the parallel postulate.We consider three versions of Euclid’s parallel postulate. The two most important are Euclid’s own formulation in his Postulate 5, which says that under certain conditions two lines meet, and Playfair’s axiom, which says there cannot be two distinct parallels to line L through the same point p. These differ in that Euclid 5 makes an existence assertion, while Playfair’s axiom does not. The third variant, which we call the strong parallel postulate, isolates the existence assertion from the geometry: it amounts to Playfair’s axiom plus the principle that two distinct lines that are not parallel do intersect. The first main result of this paper is that Euclid 5 suffices to define coordinates, addition, multiplication, and square roots geometrically.We completely settle the questions about implications between the three versions of the parallel postulate. The strong parallel postulate easily implies Euclid 5, and Euclid 5 also implies the strong parallel postulate, as a corollary of coordinatization and definability of arithmetic. We show that Playfair does not imply Euclid 5, and we also give some other independence results. Our independence proofs are given without discussing the exact choice of the other axioms of geometry; all we need is that one can interpret the geometric axioms in Euclidean field theory. The independence proofs use Kripke models of Euclidean field theories based on carefully constructed rings of real-valued functions. “Field elements” in these models are real-valued functions. (shrink)

L’article a pour but d’analyser la conception de la géométrie et de la mesure présentée dans Intuition et Raisonnement [Hölder 1900], « Les axiomes de la grandeur et la théorie de la mensuration » [Hölder 1901] et La Méthode mathématique [Hölder 1924]. L’article examine les relations entre a) la démarcation introduite par Hölder entre géométrie et arithmétique à partir de la notion de ‘concept donné’, b) sa position philosophique par rapport à l’apriorisme kantien et à l’empirisme et c) le choix (...) du postulat de la continuité de Dedekind parmi les axiomes de la théorie des grandeurs. L’article montre que les choix faits au niveau axiomatique sont reliés au cadre épistémologique et que l’originalité de Hölder consiste surtout dans son analyse au cas par cas des procédures déductives en mathématiques.The aim of the paper is to analyze Hölder’s understanding of geometry and measurement presented in Intuition and Reasoning [Hölder 1900], “The Axioms of Quantity and the Theory of Measurement” [Hölder 1901], and The Mathematical Method [Hölder 1924]. The paper explores the relations between a) Hölder’s demarcation of geometry from arithmetic based on the notion of given concepts, b) his philosophical stance towards Kantian apriorism and empiricism, and c) the choice of Dedekind’s continuity in the axiomatic formulation of the theory of magnitudes. The paper shows that the choices made at the axiomatic level reflect Hölder’s epistemological framework, and individuates the originality of his approach in the case by case analysis of deductive procedures. (shrink)

Hume’s discussion of space, time, and mathematics at T 1.2 appeared to many earlier commentators as one of the weakest parts of his philosophy. From the point of view of pure mathematics, for example, Hume’s assumptions about the infinite may appear as crude misunderstandings of the continuum and infinite divisibility. I shall argue, on the contrary, that Hume’s views on this topic are deeply connected with his radically empiricist reliance on phenomenologically given sensory images. He insightfully shows that, working within (...) this epistemological model, we cannot attain complete certainty about the continuum but only at most about discrete quantity. Geometry, in contrast to arithmetic, cannot be a fully exact science. A number of more recent commentators have offered sympathetic interpretations of Hume’s discussion aiming to correct the older tendency to dismiss this part of the Treatise as weak and confused. Most of these commentators interpret Hume as anticipating the contemporary idea of a finite or discrete geometry. They view Hume’s conception that space is composed of simple indivisible minima as a forerunner of the conception that space is a discretely (rather than continuously) ordered set. This approach, in my view, is helpful as far as it goes, but there are several important features of Hume’s discussion that are not sufficiently appreciated. I go beyond these recent commentators by emphasizing three of Hume’s most original contributions. First, Hume’s epistemological model invokes the “confounding” of indivisible minima to explain the appearance of spatial continuity. Second, Hume’s sharp contrast between the perfect exactitude of arithmetic and the irremediable inexactitude of geometry reverses the more familiar conception of the early modern tradition in pure mathematics, according to which geometry (the science of continuous quantity) has its own standard of equality that is independent from and more exact than any corresponding standard supplied by algebra and arithmetic (the sciences of discrete quantity). Third, Hume has a developed explanation of how geometry (traditional Euclidean geometry) is nonetheless possible as an axiomatic demonstrative science possessing considerably more exactitude and certainty that the “loose judgements” of the vulgar. (shrink)

In his Rules for the Direction of the Mind, Descartes elevates arithmetic and geometry to the status of paradigms for all the sciences, because of the potential for certainty in their results. This emphasis on certainty is present throughout the Cartesian corpus, but in the Rules and other early works the substance dualism characteristic of Cartesian philosophy is not as obvious. However, when several key concepts from this early work are considered together, it becomes clear that Cartesian dualism necessarily (...) follows. The most important of these concepts are: Descartes’s rejection of the Scholastic theory of sense data in favor of a telecommunicative theory of perception; his innovative reconceptualization of mathematics in which he treats number and magnitude as interchangeable, making use of the symbolism of algebra; his frequent use of visual metaphors to describe perception in general, as well as other cognitive activity. It is in consideration of this third point that Descartes’s treatment of the imagination shows its importance, for the relationship of the imagination to the intellect parallels that of geometric figures to algebraic formulae. Though the role of the imagination in the Rules seems to make the status of a dualist ontology in this work more ambiguous, this paper will argue that in fact it is precisely in the treatment of imagination that one can find the traces of a fully developed substance dualism. (shrink)

Most commentators agree that (part of what) Kant means by characterizing the propositions of geometry as synthetic is that they are not true merely in virtue of logic or meaning, and that this characterization has something to do with his views about the construction of geometrical concepts in intuition. Many commentators regard construction in intuition as an essential part of geometrical proofs on Kant’s view. On this reading, the propositions of geometry are synthetic because the geometrical theorems cannot (...) be proved in purely conceptual or logical terms. Other commentators see the main role of pure intuition and the figures constructed in pure intuition in that they provide a model for Euclidean geometry. On views of this kind, the propositions of geometry are synthetic because the geometrical axioms are substantive truths about one of our forms of intuition. On the interpretation proposed in this essay, what Kant means by claiming that the propositions of geometry are synthetic is not only that the Euclidean axioms and theorems cannot be reduced to tautologies or logical truths, but also that they apply to really possible objects. Construction in intuition plays no essential role in (what we now call) ‘pure’ geometry on Kant’s view. But the fact that the concepts of geometry can be constructed in intuition is of crucial importance in the context of Kant’s transcendental philosophy of geometry, because, among other things, it allows him to explain how Euclidean geometry is possible as an a priori synthetic science in the sense just indicated. (shrink)

This work aim to analyse relations between Arithmetic and Geometry indicated by Piero della Francesca in his treatise Libellus de quinque corporibus regularibus. Piero della Francesca was a painter and scholar of perspective, geometry and arithmetic, in his time. He carried out investigations on pictorial, geometric and architectural issues. Of the treatises he wrote, only three are preserved, on perspective, Geometry and Arithmetic. The central document selected for this research was the manuscript Libellus de quinque corporibus regularibus, (...) deposited in the Vatican Apostolic Library in digitized copy. Throughout this work we have tried to understand the Libellus de quinque corporibus regularibus as a result of the work of an artist and scholar who proposed ways of relating Arithmetic and Geometry using both his practical knowledge and the works of authors of antiquity. (shrink)

The paper discusses the similarity between geometry, arithmetic, and logic, specifically with respect to the question of whether applied theories of each may be revised. It argues that they can - even when the revised logic is a paraconsistent one, or the revised arithmetic is an inconsistent one. Indeed, in the case of logic, it argues that logic is not only revisable, but, during its history, it has been revised. The paper also discusses Quine's well known argument against the (...) possibility of logical deviancy. (shrink)

The paper discusses the similarity between geometry, arithmetic, and logic, specifically with respect to the question of whether applied theories of each may be revised. It argues that they can - even when the revised logic is a paraconsistent one, or the revised arithmetic is an inconsistent one. Indeed, in the case of logic, it argues that logic is not only revisable, but, during its history, it has been revised. The paper also discusses Quine's well known argument against the (...) possibility of “logical deviancy”. (shrink)

This is the first critical edition of the first and second Epistles of the Brethren Purity--the Rasa 'il--in Arabic with a fully annotated English translation. It presents technical and epistemic analyses of mathematical concepts and their metaphysical bases, and an overview of the mathematical sciences within Islamic intellectual milieu.

This paper explores the classical idea of complementarity in mathematics concerning the relationship of intuition and axiomatic proof. Section I illustrates the basic concepts of the paper, while Section II presents opposing accounts of intuitionist and axiomatic approaches to mathematics. Section III analyzes one of Einstein's lecture on the topic and Section IV examines an application of the issues in mathematics and science education. Section V discusses the idea of complementarity by examining one of Zeno's paradoxes. This is followed by (...) presenting a few more programmatic suggestions and a brief summary. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:142 HISTORY OF PHILOSOPHY Das literarische und kiinstlerische Werk. By Rudolf Steiner. Eine bibliographische Uebersicht, 1961. (Dornaeh: 1961. Pp. 277.) This is a complete list of the writings, lectures, and artistic creations of the founder of Anthroposophy, Dr. Rudolf Steiner (1861-1925). It is, in addition, a description of the Temple of Anthroposophy, the "Goetheanum" in Dornach built after the ideas of Steiner, of his "mystery-plays," of his ideas on (...) "eurhythmy," of his designs of furnishings for the "Goetheanum," of his sculptural suggestions, etc. Thus, the booklet encompasses the whole life-work of Steiner and was published in 1961 at the 100th anniversary of his birth. It is prefaced by a biographical sketch based on Steiner's "Autobiography." Rudolf Steiner was the son of a railway employer from Lower Austria. He studied first in technical high schools (Realschule) in the neighborhood of the Austrian capital and then in the Technical University of u In the high school, he was already most impressed by the study of geometry and arithmetic because they seemed to show that there is an independent realm of thought not connected with the world of senses. This conviction led him to a lifelong search for a spiritual world beyond and above the visible world. While this impulse was rather scientific than religious, it led him also into the theosophical movement, then headed by Mrs. Annie Besant in London. But this connection was broken when Mrs. Besant wanted to appoint a young Hindu to be a reincarnation of Christ. This was unacceptable to Steiner and he founded the independent anthroposophical movement in Germany where he spent most of his life writing, teaching, and lecturing. His first writings were commentaries to the work~ of Goethe oa natural sciences. Goethe thus became the "heros eponymus" of Anthroposophy. In 1913, Steiner started to build the Temple of Anthroposophy at Dornaeh (Switzerland) which he called "Goetheanum." This temple, the details of the structure, its style, its furniture were supposed to be symbolical of.the ideas contained in Anthroposophy. In a cycle of lectures entitled "What was the purpose of the Goetheanum?" and "What is the purpose of Anthroposophy?" he states that this aim was the "exaltation of the human cognitive power into imagination, inspiration, and intuition." The results of this exaltation were a somewhat complicated and phantastic mysticism. The Goetheanum, which, for symbolical reasons, was built of wood, burned to the ground in 1922. Starting in 1924, it was replaced by a building in concrete. Steiner did not live to see the reconstructed Temple because he died in 1925. Steiner tried to invent new forms of art in his Goetheanum, new forms of dramatic poetry in his mystery-plays, and new forms of a spiritualized symbolic dance in his "eurhythmy." His life-work is prodigious. Apart from his writings he gave some 6,000 lectures. MAx RIESER New York City Gegenw~rtiges und Vergangenes im Menschengeiste. By Rudolf Steiner. (Dornach: 1962. Pp. 308.) This is a new printing in the framework of the Collected Works of Rudolf Steiner of twelve lectures given during World War I in Berlin in 1916. These lectures are historically interesting since they refer to contemporary publications in Germany and Austria, but they also offer in nuce the main elements of "Anthroposophy" in the form of an anthroposophical anthropology and also of an anthroposophical philosophy of cosmic and human history. The whole is based on the assumption of the existence of a spiritual world paralleling the physical world. This anthropology is aimed at the refutation of the materialistic conceptions based on the natural sciences of that time. Steiner thinks that a man built according to the ideas of the natural sciences would not be a living being but a sort of "homunculus," i.e., an automaton. Apart from the physical body, man has an "ethereal body," an "astral body," and an "Ego." These three entities do not die a physical death. In addition they represent the world of animals, of plants, and of minerals, respectively, incorporated in man. There are also different epochs of human development in which the relationship of the spiritual parts of the human being were not related to each other in the same... (shrink)

In lieu of an abstract, here is a brief excerpt of the content:142 HISTORY OF PHILOSOPHY Das literarische und kiinstlerische Werk. By Rudolf Steiner. Eine bibliographische Uebersicht, 1961. (Dornaeh: 1961. Pp. 277.) This is a complete list of the writings, lectures, and artistic creations of the founder of Anthroposophy, Dr. Rudolf Steiner (1861-1925). It is, in addition, a description of the Temple of Anthroposophy, the "Goetheanum" in Dornach built after the ideas of Steiner, of his "mystery-plays," of his ideas on (...) "eurhythmy," of his designs of furnishings for the "Goetheanum," of his sculptural suggestions, etc. Thus, the booklet encompasses the whole life-work of Steiner and was published in 1961 at the 100th anniversary of his birth. It is prefaced by a biographical sketch based on Steiner's "Autobiography." Rudolf Steiner was the son of a railway employer from Lower Austria. He studied first in technical high schools (Realschule) in the neighborhood of the Austrian capital and then in the Technical University of u In the high school, he was already most impressed by the study of geometry and arithmetic because they seemed to show that there is an independent realm of thought not connected with the world of senses. This conviction led him to a lifelong search for a spiritual world beyond and above the visible world. While this impulse was rather scientific than religious, it led him also into the theosophical movement, then headed by Mrs. Annie Besant in London. But this connection was broken when Mrs. Besant wanted to appoint a young Hindu to be a reincarnation of Christ. This was unacceptable to Steiner and he founded the independent anthroposophical movement in Germany where he spent most of his life writing, teaching, and lecturing. His first writings were commentaries to the work~ of Goethe oa natural sciences. Goethe thus became the "heros eponymus" of Anthroposophy. In 1913, Steiner started to build the Temple of Anthroposophy at Dornaeh (Switzerland) which he called "Goetheanum." This temple, the details of the structure, its style, its furniture were supposed to be symbolical of.the ideas contained in Anthroposophy. In a cycle of lectures entitled "What was the purpose of the Goetheanum?" and "What is the purpose of Anthroposophy?" he states that this aim was the "exaltation of the human cognitive power into imagination, inspiration, and intuition." The results of this exaltation were a somewhat complicated and phantastic mysticism. The Goetheanum, which, for symbolical reasons, was built of wood, burned to the ground in 1922. Starting in 1924, it was replaced by a building in concrete. Steiner did not live to see the reconstructed Temple because he died in 1925. Steiner tried to invent new forms of art in his Goetheanum, new forms of dramatic poetry in his mystery-plays, and new forms of a spiritualized symbolic dance in his "eurhythmy." His life-work is prodigious. Apart from his writings he gave some 6,000 lectures. MAx RIESER New York City Gegenw~rtiges und Vergangenes im Menschengeiste. By Rudolf Steiner. (Dornach: 1962. Pp. 308.) This is a new printing in the framework of the Collected Works of Rudolf Steiner of twelve lectures given during World War I in Berlin in 1916. These lectures are historically interesting since they refer to contemporary publications in Germany and Austria, but they also offer in nuce the main elements of "Anthroposophy" in the form of an anthroposophical anthropology and also of an anthroposophical philosophy of cosmic and human history. The whole is based on the assumption of the existence of a spiritual world paralleling the physical world. This anthropology is aimed at the refutation of the materialistic conceptions based on the natural sciences of that time. Steiner thinks that a man built according to the ideas of the natural sciences would not be a living being but a sort of "homunculus," i.e., an automaton. Apart from the physical body, man has an "ethereal body," an "astral body," and an "Ego." These three entities do not die a physical death. In addition they represent the world of animals, of plants, and of minerals, respectively, incorporated in man. There are also different epochs of human development in which the relationship of the spiritual parts of the human being were not related to each other in the same... (shrink)

Sobre la base que aportan las notas manuscritas de David Hilbert para cursos sobre geometría, el artículo procura contextualizar y analizar una de las contribuciones más importantes y novedosas de su célebre monografía Fundamentos de la geometría, a saber: el cálculo de segmentos lineales. Se argumenta que, además de ser un resultado matemático importante, Hilbert depositó en su aritmética de segmentos un destacado significado epistemológico y metodológico. En particular, se afirma que para Hilbert este resultado representaba un claro ejemplo de (...) uno de los rasgos más fructíferos y atractivos de su nuevo método axiomático formal, o sea, la capacidad de descubrir y exhibir conexiones estructurales o internas entre diferentes teorías matemáticas. On the basis of a set of unpublished notes for lecture courses on geometry, the paper seeks to contextualize and analyze one of the most important and original contributions of David Hilbert's celebrated monograph Foundations of Geometry, namely its arithmetic of line segments. It is argued that Hilbert attributed to his arithmetic of segments an important epistemological and methodological meaning, in addition to its relevance as an original mathematical result. In particular, it is claimed that for Hilbert his arithmetic of segments represented a clear example of one of the most fruitful and attractive traits of his new formal axiomatic method, i.e., the power to discover and exhibit inner or structural connections among different mathematical theories. (shrink)

Summary The philosophical implications associated with the choice of a particular geometry required for the formulation of a dynamics at subnuclear distances are discussed. A dualism between geometry and matter — the former identified with a fiber bundle of Cartan type raised over space-time, the latter represented by a generalized quantum mechanical wave function — is presented as a possible framework for the dynamics of strongly interacting particles at distances of 10-13 cm.

The critique of my protophysical approaches to operational foundation of geometry by Lucas Amiras (Journal for General Philosophy of Science Vol. 34 (2003)) concerns my first publication from 1976 but not the further 30 years of work. It does not offer any argument leading from the (erroneous) judgement “lacking success” to the conclusion “impossible”. And it is, in general, based on a philosophical defect: it ignores the principle of methodical order as leading for constructivist protophysics.

The paper investigates Ernst Cassirer’s structuralist account of geometrical knowledge developed in his Substanzbegriff und Funktionsbegriff. The aim here is twofold. First, to give a closer study of several developments in projective geometry that form the direct background for Cassirer’s philosophical remarks on geometrical concept formation. Specifically, the paper will survey different attempts to justify the principle of duality in projective geometry as well as Felix Klein’s generalization of the use of geometrical transformations in his Erlangen program. The (...) second aim is to analyze the specific character of Cassirer’s geometrical structuralism formulated in 1910 as well as in subsequent writings. As will be argued, his account of modern geometry is best described as a “methodological structuralism”, that is, as a view mainly concerned with the role of structural methods in modern mathematical practice. (shrink)

Edmund Husserl has argued that we can intuit essences and, moreover, that it is possible to formulate a method for intuiting essences. Husserl calls this method ‘ideation’. In this paper I bring a fresh perspective to bear on these claims by illustrating them in connection with some examples from modern pure geometry. I follow Husserl in describing geometric essences as invariants through different types of free variations and I then link this to the mapping out of geometric invariants in (...) modern mathematics. This view leads naturally to different types of spatial ontologies and it can be used to shed light on Husserl's general claim that there are different ontologies in the eidetic sciences that can be systematically related to one another. The paper is rounded out with a consideration of the role of ideation in the origins of modern geometry, and with a brief discussion of the use of ideation outside of pure geometry. What would be the study that would draw the soul away from the world of becoming to the world of being?… Geometry and arithmetic would be among the studies we are seeking … a philosopher must learn them because he must arise out of the region of generation and lay hold on essence or he can never become a true reckoner … they facilitate the conversion of the soul itself from the world of generation to essence and truth… they are knowledge of that which always is and not of something which at some time comes into being and passes away. (shrink)