This text is an outgrowth of notes prepared by J. Y. Girard for a course at the University of Paris VII. It deals with the mathematical background of the application to computer science of aspects of logic (namely the correspondence between proposition & types). Combined with the conceptual perspectives of Girard's ideas, this sheds light on both the traditional logic material & its prospective applications to computer science. The book covers a very active & exciting research area, & it will (...) be essential reading for all those working in logic & computer science. (shrink)
The hexagon of opposition is an improvement of the square of opposition due to Robert Blanché. After a short presentation of the square and its various interpretations, we discuss two important problems related with the square: the problem of the I-corner and the problem of the O-corner. The meaning of the notion described by the I-corner does not correspond to the name used for it. In the case of the O-corner, the problem is not a wrong-name problem but a no-name (...) problem and it is not clear what is the intuitive notion corresponding to it. We explain then that the triangle of contrariety proposed by different people such as Vasiliev and Jespersen solves these problems, but that we don’t need to reject the square. It can be reconstructed from this triangle of contrariety, by considering a dual triangle of subcontrariety. This is the main idea of Blanché’s hexagon. We then give different examples of hexagons to show how this framework can be useful to conceptual analysis in many different fields such as economy, music, semiotics, identity theory, philosophy, metalogic and the metatheory of the hexagon itself. We finish by discussing the abstract structure of the hexagon and by showing how we can swing from sense to non-sense thinking with the hexagon. (shrink)
Jean-Jacques Rousseau est l'auteur de l'entrée "économie politique" dans l'Encyclopédie en 1755. A ce titre, il aurait pu être l'un des fondateurs de cette discipline. Pourtant, la définition qu'il en donne est à l'encontre de la pensée libérale des physiocrates, puis des classiques, et constitue une véritable "anti-économique". En hypertrophiant le rôle de l'Etat et en niant l'intérêt personnel, Rousseau est au contraire l'un des pères du socialsme. En niant la liberté humaine, il nie aussi l'existence de choix éthiques.
This is a collection of new investigations and discoveries on the theory of opposition (square, hexagon, octagon, polyhedra of opposition) by the best specialists from all over the world. The papers range from historical considerations to new mathematical developments of the theory of opposition including applications to theology, theory of argumentation and metalogic.
This paper introduces the special issue on Logic and Religion of the journal Logica Universalis (Springer). The issue contains the following articles: Logic and Religion, by Jean-Yves Beziau and Ricardo Silvestre; Thinking Negation in Early Hinduism and Classical Indian Philosophy, by Purushottama Bilimoria; Karma Theory, Determinism, Fatalism and Freedom of Will, by Ricardo Sousa Silvestre; From Logic in Islam to Islamic Logic, by Musa Akrami; Leibniz’s Ontological Proof of the Existence of God and the Problem of Impossible Objects, (...) by Wolfgang Lenzen; A Logical Analysis of the Anselm’s Unum Argumentum (from Proslogion), by Jean-Pierre Desclés; Monotonic and Non-monotonic Embeddings of Anselm’s Proof, by Jacob Archambault; Computer-Assisted Analysis of the Anderson–Hájek Ontological Controversy, by C. Benzmüller, L. Weber and B. Woltzenlogel Paleo. (shrink)
Le Brouillon Project de Girard Desargues sur les coniques développe, dans sa partie centrale, la notion de traversale, notion qui généralise celle de diamètre d’Apollonius et permet d’unifier le traitement des diverses espèces de coniques. Il est souvent écrit qu’il s’agit là d’un équivalent de la polaire, concept émergeant au début du $$\hbox {XIX}{}^{\mathrm{e}}$$ XIX e siècle. Nous allons dans cet article explorer en détail les passages du texte de Desargues qui traitent de la traversale et de ses propriétés et (...) montrer comment, en tenant compte des notes ajoutées postérieurement à la rédaction du premier jet du Brouillon, on peut y reconstituer la naissance d’une nouvelle théorie, à savoir une théorie projective de la polarité associée à une conique. Nous verrons qu’outre une correspondance naturelle entre points et droites, Desargues a compris qu’une conique induisait, sur chaque droite du plan, une involution et nous montrerons comment il vient progressivement à bout des difficultés conceptuelles considérables auxquelles il doit faire face pour exprimer clairement ses idées novatrices. (shrink)
Nous tentons dans cet article de proposer une thèse cohérente concernant la formation de la notion d’involution dans le Brouillon Project de Desargues. Pour cela, nous donnons une analyse détaillée des dix premières pages dudit Brouillon, comprenant les développements de cas particuliers qui aident à comprendre l’intention de Desargues. Nous mettons cette analyse en regard de la lecture qu’en fait Jean de Beaugrand et que l’on trouve dans les Advis Charitables.
We present a single sequent calculus common to classical, intuitionistic and linear logics. The main novelty is that classical, intuitionistic and linear logics appear as fragments, i.e. as particular classes of formulas and sequents. For instance, a proof of an intuitionistic formula A may use classical or linear lemmas without any restriction: but after cut-elimination the proof of A is wholly intuitionistic, what is superficially achieved by the subformula property and more deeply by a very careful treatment of structural rules. (...) This approach is radically different from the one that consists in “changing the rule of the game” when we want to change logic, e.g. pass from one style of sequent to another: here, there is only one logic, which—depending on its use—may appear classical, intuitionistic or linear. (shrink)
We present a paraconsistent logic, called Z, based on an intuitive possible worlds semantics, in which the replacement theorem holds. We show how to axiomatize this logic and prove the completeness theorem.
Jean-Yves Le Naour et Catherine Valenti proposent un ouvrage ambitieux par son propos : faire une histoire de l'avortement depuis le milieu du XIXe jusqu'à la fin du XXe siècle. Entreprise ambitieuse mais nécessaire, une telle synthèse étant inédite en France. L'idée force du livre tient donc dans sa longue durée : un siècle et demi durant lequel la question de l'avortement fut au centre de débats tant politiques, que juridiques, économiques et sociaux. Le problème est pris à (...) bras le c.. (shrink)
These lectures on logic, more specifically proof theory, are basically intended for postgraduate students and researchers in logic. The question at stake is the nature of mathematical knowledge and the difference between a question and an answer, i.e., the implicit and the explicit. The problem is delicate mathematically and philosophically as well: the relation between a question and its answer is a sort of equality where one side is ``more equal than the other'': one thus discovers essentialist blind spots. Starting (...) with Godel's paradox --so to speak, the incompleteness of answers with respect to questions--the book proceeds with paradigms inherited from Gentzen's cut-elimination. Various settings are studied: sequent calculus, natural deduction, lambda calculi, category-theoretic composition, up to geometry of interaction, all devoted to explicitation, which eventually amounts to inverting an operator in a von Neumann algebra. Mathematical language is usually described as referring to a preexisting reality. Logical operations can be given an alternative procedural meaning: typically, the operators involved in GoI are invertible, not because they are constructed according to the book, but because logical rules are those ensuring invertibility. Similarly, the durability of truth should not be taken for granted: one should distinguish between imperfect and perfect modes. The procedural explanation of the infinite thus identifies it with the unfinished, i.e., the perennial. But is perenniality perennial? This questioning yields a possible logical explanation for algorithmic complexity. This highly original course on logic by one of the world's leading proof theorists challenges mathematicians, computer scientists, physicists, and philosophers to rethink their views and concepts on the nature of mathematical knowledge in an exceptionally profound way. (shrink)
According to Boole it is possible to deduce the principle of contradiction from what he calls the fundamental law of thought and expresses as \. We examine in which framework this makes sense and up to which point it depends on notation. This leads us to make various comments on the history and philosophy of modern logic.
Dans un texte désormais célèbre, Ferdinand de Saussure insiste sur l’arbitraire du signe dont il vante les qualités. Toutefois il s’avère que le symbole, signe non arbitraire, dans la mesure où il existe un rapport entre ce qui représente et ce qui est représenté, joue un rôle fondamental dans la plupart des activités humaines, qu’elles soient scientifiques, artistiques ou religieuses. C’est cette dimension symbolique, sa portée, son fonctionnement et sa signification dans des domaines aussi variés que la chimie, la théologie, (...) les mathématiques, le code de la route et bien d’autres qui est l’objet du livre La Pointure du symbole. -/- Jean-Yves Béziau, franco-suisse, est docteur en logique mathématique et docteur en philosophie. Il a poursuivi des recherches en France, au Brésil, en Suisse, aux États-Unis (UCLA et Stanford), en Pologne et développé la logique universelle. Éditeur-en-chef de la revue Logica Universalis et de la collection Studies in Universal Logic (Springer), il est actuellement professeur à l’Université Fédérale de Rio de Janeiro et membre de l’Académie brésilienne de Philosophie. SOMMAIRE -/- PRÉFACE L’arbitraire du signe face à la puissance du symbole Jean-Yves BÉZIAU La logique et la théorie de la notation (sémiotique) de Peirce (Traduit de l’anglais par Jean-Marie Chevalier) Irving H. ANELLIS Langage symbolique de Genèse 2-3 Lytta BASSET -/- Mécanique quantique : quelle réalité derrière les symboles ? Hans BECK -/- Quels langages et images pour représenter le corps humain ? Sarah CARVALLO Des jeux symboliques aux rituels collectifs. Quelques apports de la psychologie du développement à l’étude du symbolisme Fabrice CLÉMENT Les panneaux de signalisation (Traduit de l’anglais par Fabien Shang) Robert DEWAR Remarques sur l’émergence des activités symboliques Jean LASSÈGUE Les illustrations du "Songe de Poliphile" (1499). Notule sur les hiéroglyphes de Francesca Colonna Pierre-Alain MARIAUX Signes de vie Jeremy NARBY Visualising relations in society and economics. Otto Neuraths Isotype-method against the background of his economic thought Elisabeth NEMETH Algèbre et logique symboliques : arbitraire du signe et langage formel Marie-José DURAND – Amirouche MOKTEFI Les symboles mathématiques, signes du Ciel Jean-Claude PONT La mathématique : un langage mathématique ? Alain M. ROBERT. (shrink)
We discuss the origin and development of the universal logic project. We describe in particular the structure of UNILOG, a series of events created for promoting the universal logic project, with a school, a congress, a secret speaker and a contest. We explain how the contest has evolved into a session of logic prizes.
After recalling the distinction between logic as reasoning and logic as theory of reasoning, we first examine the question of relativity of logic arguing that the theory of reasoning as any other science is relative. In a second part we discuss the emergence of universal logic as a general theory of logical systems, making comparison with universal algebra and the project of mathesis universalis. In a third part we critically present three lines of research connected to universal logic: logical pluralism, (...) non-classical logics and cognitive science. (shrink)
In the middle part of his Brouillon Project on conics, Girard Desargues develops the theory of the traversale, a notion that generalizes the Apollonian diameter and allows to give a unified treatment of the three kinds of conics. We showed elsewhere that it leads Desargues to a complete theory of projective polarity for conics. The present article, which shall close our study of the Brouillon Project, is devoted to the last part of the text, in which Desargues puts his theory (...) of the traversal into practice by giving a very elegant tratment of the classical theory of parameters and foci. This will lead us to show that Desargues’ proofs can only be understood if one accepts that he reasons in a resolutely projective framework, completely assimilating elements at infinity to those at finite distance in his proofs. (shrink)
Jean-Yves Béziau Abstract In this paper I relate the story about the new rising of the square of opposition: how I got in touch with it and started to develop new ideas and to organize world congresses on the topic with subsequent publications.
The present book discusses all aspects of paraconsistent logic, including the latest findings, and its various systems. It includes papers by leading international researchers, which address the subject in many different ways: development of abstract paraconsistent systems and new theorems about them; studies of the connections between these systems and other non-classical logics, such as non-monotonic, many-valued, relevant, paracomplete and fuzzy logics; philosophical interpretations of these constructions; and applications to other sciences, in particular quantum physics and mathematics. Reasoning with contradictions (...) is the challenge of paraconsistent logic. The book will be of interest to graduate students and researchers working in mathematical logic, computer science, philosophical logic, linguistics and physics. (shrink)
Contradiction is often confused with contrariety. We propose to disentangle contrariety from contradiction using the hexagon of opposition, providing a clear and distinct characterization of three notions: contrariety, contradiction, incompatibility. At the same time, this hexagonal structure describes and explains the relations between them.
Un mot d'usage quotidien, "danger", est devenu concept chez Heidegger. L'usage heideggerien de "danger" n'est pourtant pas celui de ce livre, qui refuse de s'engager de front dans la "question de l'être" au profit des manières ou modes d'être, dont il explore un échantillon sans prétention exhaustive mais utilisé comme trame heuristique. Mode d'être de l'oeuvre d'art, mode d'être de la "chose" ou du sacrement, mode d'être comme "existence" et comme "vie", un danger est toujours présent : l'existence, telle que (...) décrite chez Heidegger, est déconstituée par des phénomènes auxquels elle ne peut rendre justice ; la vie abrite l'existence mais court le risque perpétuel de n'être que dans les frontières de l'existence, etc. Et si l'étant nous est toujours donné dans un comment - comment de son apparaître, donc comment de son être -, rien ne garantit la pérennité de cette donation : presque tout étant, et d'abord l'étant que nous sommes, est en danger d'apparaître autre qu'il ne nous apparaît maintenant. Aussi convenait-il, après avoir ajointé le concept de vie à celui d'esprit, après avoir dit que la vie est "spirituelle", de justifier le titre du livre en liant "être" et "danger" ; et il restait au final le temps de proposer, dans l'élément du possible, l'hypothèse d'une eschatologie de l'être, avant tout de notre être, sur laquelle le danger n'aurait plus de prise. (shrink)
In this article Schrijvers elaborates on the work of Jean-Yves Lacoste. In Expérience et Absolu , this French phenomenologist and theologian coins the ‘liturgic experience’. Such an experience is conceived of as a correction to the Heideggerian picture of finitude. While for Heidegger Dasein is a being towards the future and, most importantly, towards his own death, Lacoste wants to warrant the present as an area of meaning and sense. One such example is the liturgic experience, in which (...) the faithful undergo the nearness of God in the present. However, this experience must sharply be distinguished from the ‘religious experience’ as it is known in the works of Otto and Schleiermacher. The liturgic experience is the confrontation with the Christian God who does not appear objectively. Therefore the liturgic experience is a nonexperience. It is a brutal conversion of the believer to the image of Christ, who on the Cross had no experience of God whatsoever. Liturgy connotates a violent rupture with the world, and the experiences therein. In later works, Schrijvers contends, Lacoste corrects this Barthian scheme of liturgy: attention is now paid to the work of art as well as to the experience of resting as examples of an analogous rupture with Heideggers ‘being-in-the-world’. These experiences give back the Christian ‘being there’ its human character and recognizability: faith can be elucidated from the ruptures brought forth by the work of art and with the experience of resting in mind. The reflections on art are accompanied by an ontology of affectivity. ‘Older’ than the Heideggerian ‘world’ or ‘earth’ is our free and affective response to reality. This affective response is so rich that ‘being’ cannot and may not be reduced to Heidegger’s options: in between world and earth one encounters an open and indeterminate space that points to the irreducibility of being to its Heideggerian features. The experience of the work of art and liturgy, and their respective joyful present, can thus be given ontological weight. To conclude, Schrijvers examines I. Verhacks critical review of Lacostes book. The author tries to show that the Barthian scheme of liturgy is not solely due to the lack of a philosophical elucidation of the liturgic ‘being there’, as Verhack argues, but also, and foremost, to the lack of relation between God and world. This will be the occasion to conceive of the religious person as protesting against the Absolute. Is not the non-experience of liturgy the consequence of an ontotheological conception of the desire of God, and is it possible to understand theologically the protest against and refusal of one’s own non-experience as an unredeemedness? (shrink)
This essay offers a commentary of Jean-Yves Lacoste’s most recent book Théses sur le vrai. It does so through a close reading of the book’s main arguments and through relating this most recent work to Lacoste’s earlier thinking. Lacoste here offers a new introduction to his body of work by elaborating on the phenomenological experience of truth. Truth, Lacoste argues, is first and foremost experienced in experiences of newness and in experiences offered through poetry. These experiences show and (...) manifest the truth as “unexpected.” Such a surprise, for Lacoste, can be read as a secular translation of what theology calls the “good news.” The book concludes with new insights in Lacoste’s thinking of the relation between philosophy and theology. (shrink)
In this paper we explain that the paraconsistent logic LP promoted by Graham Priest can only be supported by trivial dialetheists, i.e., those who believe that all sentences are dialetheias.
We discuss a theory presented in a posthumous paper by Alfred Tarski entitled “What are logical notions?”. Although the theory of these logical notions is something outside of the main stream of logic, not presented in logic textbooks, it is a very interesting theory and can easily be understood by anybody, especially studying the simplest case of the four basic logical notions. This is what we are doing here, as well as introducing a challenging fifth logical notion. We first recall (...) the context and origin of what are here called Tarski-Lindenbaum logical notions. In the second part, we present these notions in the simple case of a binary relation. In the third part, we examine in which sense these are considered as logical notions contrasting them with an example of a nonlogical relation. In the fourth part, we discuss the formulations of the four logical notions in natural language and in first-order logic without equality, emphasizing the fact that two of the four logical notions cannot be expressed in this formal language. In the fifth part, we discuss the relations between these notions using the theory of the square of opposition. In the sixth part, we introduce the notion of variety corresponding to all non-logical notions and we argue that it can be considered as a logical notion because it is invariant, always referring to the same class of structures. In the seventh part, we present an enigma: is variety formalizable in first-order logic without equality? There follow recollections concerning Jan Woleński. This paper is dedicated to his 80th birthday. We end with the bibliography, giving some precise references for those wanting to know more about the topic. (shrink)
Les animaux peuvent-ils avoir des droits? La souffrance animale a-t-elle une importance morale? Les animaux sont-ils dotés de conscience? Telles sont les questions abordées dans cet ouvrage, qui se propose d’approfondir quelques pistes de réflexion à travers la lecture commentée de deux textes, l’un de John Stuart Mill , l’autre de Donald Davidson.
We present the logic K/2 which is a logic with classical implication and only the left part of classical negation.We show that it is possible to define a classical negation into K/2 and that the classical proposition logic K can be translated into this apparently weaker logic.We use concepts from model-theory in order to characterized rigorously this translation and to understand this paradox. Finally we point out that K/2 appears, following Haack's distinction, both as a deviation and an extension of (...) K. (shrink)
This special issue of Logica Universalis (Springer) deals with the relations between logic and religion, broadly conceived. It contains the following articles: Logic and Religion, by Jean-Yves Beziau and Ricardo Silvestre; Thinking Negation in Early Hinduism and Classical Indian Philosophy, by Purushottama Bilimoria; Karma Theory, Determinism, Fatalism and Freedom of Will, by Ricardo Sousa Silvestre; From Logic in Islam to Islamic Logic, by Musa Akrami; Leibniz’s Ontological Proof of the Existence of God and the Problem of Impossible Objects, (...) by Wolfgang Lenzen; A Logical Analysis of the Anselm’s Unum Argumentum (from Proslogion), by Jean-Pierre Desclés; Monotonic and Non-monotonic Embeddings of Anselm’s Proof, by Jacob Archambault; Computer-Assisted Analysis of the Anderson–Hájek Ontological Controversy, by C. Benzmüller, L. Weber and B. Woltzenlogel Paleo. (shrink)
Que la musique soit faite pour etre ecoutee semble une evidence, et pourtant... C'est pour guider les melomanes et les aider a passer d'une audition passive a une ecoute active que Jean-Yves Bras partage ici son experience d'ecouteur. Apres avoir defini ce qu'est la musique, il s'interroge ensuite sur la nature de l'ecoute: que faut-il entendre par ecouter? Sur quoi porter notre attention? Comment ecouter? Les conditions materielles dans lesquelles nous consommons la musique, notre comportement au concert ou (...) a l'ecoute d'un disque, ont egalement une incidence importante sur la qualite de notre ecoute. Puis il analyse ces liens si mysterieux et si essentiels tisses entre compositeurs, interpretes et nous-memes, auditeurs. Enfin, il trace a grands traits l'histoire de nos oreilles de l'Antiquite a nos jours, pour conclure sur les differentes categories d'auditeurs actuels. Parallelement, l'auteur a cree un site Internet, www.artdecouter.fr, qui apporte un complement d'information agremente d'exemples sonores. Ce chemin d'initiation se parcourt sous forme de dialogue: une jeune personne souhaitant s'instruire, Mademoiselle Croche, nous permet par ses questions d'entendre s'ouvrir pour nous le langage de la musique. Jean-Yves Bras a ete directeur de la Documentation musicale de Radio France et a participe a de nombreuses emissions. Responsable artistique du Festival Chopin a Paris, il est l'auteur des Courants musicaux du XXe siecle et d'un ouvrage sur le chef d'orchestre Carlo Maria Giulini. (shrink)