The development of symbolic logic is often presented in terms of a cumulative story of consecutive innovations that led to what is known as modern logic. This narrative hides the difficulties that this new logic faced at first, which shaped its history. Indeed, negative reactions to the emergence of the new logic in the second half of the nineteenth century were numerous and we study here one case, namely logic at Oxford, where one finds Lewis Carroll, a mathematical teacher who (...) promoted symbolic logic, and John Cook Wilson, the Wykeham Professor of Logic who notoriously opposed it. An analysis of their disputes on the topic of logical symbolism shows that their opposition was not as sharp as it might look at first, as Cook Wilson was not so much opposed to the « symbolic » character of logic, but the intrusion of mathematics and what he perceived to be the futility of some of its problems, for logicians and philosophers alike. (shrink)
This pioneering book demonstrates the crucial importance of Wittgenstein's philosophy of mathematics to his philosophy as a whole. Marion traces the development of Wittgenstein's thinking in the context of the mathematical and philosophical work of the times, to make coherent sense of ideas that have too often been misunderstood because they have been presented in a disjointed and incomplete way. In particular, he illuminates the work of the neglected 'transitional period' between the Tractatus and the Investigations.
This paper is an interim report of joint work begun in on dialectic from Parmenides to Aristotle. In the first part we present rules for dialectical games, understood as a specific form of antilogikê developed by philosophers, and explain some of the key concepts of these dialectical games in terms of ideas from game semantics. In the games we describe, for a thesis A asserted by the answerer, a questioner must elicit the answerer’s assent to further assertions B1, B2,…, Bn, (...) which form a scoreboard from which the questioner seeks to infer an impossibility ; we explain why the questioner must not insert any of his own assertions in the scoreboard, as well as the crucial role the Law of Non Contradiction, and why the games end with the inference to an impossibility, as opposed to the assertion of ¬A. In the second part we introduce some specific characteristics of Eleatic Antilogic as a method of enquiry. When Antilogic is used as a method of inquiry, then one must play not only the game beginning with a given thesis A, but also the game for ¬A as well as for A & ¬A, while using a peculiar set of opposite predicates to generate the arguments. In our discussion we hark back to Parmenides’ Poem, and illustrate our points with Zeno’s arguments about divisibility, Gorgias’ ontological argument from his treatise On Not-Being, and the second part of Plato’s Parmenides. We also identify numerous links to Aristotle, and conclude with some speculative comments on the origin of logic. (shrink)
In this paper, elementary but hitherto overlooked connections are established between Wittgenstein's remarks on mathematics, written during his transitional period, and free-variable finitism. After giving a brief description of theTractatus Logico-Philosophicus on quantifiers and generality, I present in the first section Wittgenstein's rejection of quantification theory and his account of general arithmetical propositions, to use modern jargon, as claims (as opposed to statements). As in Skolem's primitive recursive arithmetic and Goodstein's equational calculus, Wittgenstein represented generality by the use of free (...) variables. This has the effect that negation of unbounded universal and existential propositions cannot be expressed. This is claimed in the second section to be the basis for Wittgenstein's criticism of the universal validity of the law of excluded middle. In the last section, there is a brief discussion of Wittgenstein's remarks on real numbers. These show a preference, in line with finitism, for a recursive version of the continuum. (shrink)
After sketching an argument for radical anti-realism that does not appeal to human limitations but polynomial-time computability in its definition of feasibility, I revisit an argument by Wittgenstein on the surveyability of proofs, and then examine the consequences of its application to the notion of canonical proof in contemporary proof-theoretical-semantics.
In this paper, I present a summary of the philosophical relationship betweenWittgenstein and Brouwer, taking as my point of departure Brouwer's lecture onMarch 10, 1928 in Vienna. I argue that Wittgenstein having at that stage not doneserious philosophical work for years, if one is to understand the impact of thatlecture on him, it is better to compare its content with the remarks on logics andmathematics in the Tractactus. I thus show that Wittgenstein's position, in theTractactus, was already quite close to (...) Brouwer's and that the points of divergence are the basis to Wittgenstein's later criticisms of intuitionism. Among the topics of comparison are the role of intuition in mathematics, rule following, choice sequences, the Law of Excluded Middle, and the primacy of arithmetic over logic. (shrink)
This volume portrays the Polish or Lvov-Warsaw School, one of the most influential schools in analytic philosophy, which, as discussed in the thorough introduction, presented an alternative working picture of the unity of science.
John Cook Wilson (1849–1915) was Wykeham Professor of Logic at New College, Oxford and the founder of ‘Oxford Realism’, a philosophical movement that flourished at Oxford during the first decades of the 20th century. Although trained as a classicist and a mathematician, his most important contribution was to the theory of knowledge, where he argued that knowledge is factive and not definable in terms of belief, and he criticized ‘hybrid’ and ‘externalist’ accounts. He also argued for direct realism in perception, (...) criticizing both empiricism and idealism, and argued for a moderate nominalist view of universals as being in rebus and only ‘apprehended’ by their particulars. His influence helped swaying Oxford away from idealism and, through figures such as H. A. Prichard, Gilbert Ryle, or J. L. Austin, his ideas were also to some extent at the origin of ‘moral intuitionism’ and ‘ordinary language philosophy’ which defined much of Oxford philosophy until the second half of the twentieth-century. Nevertheless, his name and legacy were all but forgotten for generations after World War II. Still, his views on knowledge are with us today, being in part at work in the writings of philosophers as diverse as John McDowell, Charles Travis, and Timothy Williamson. (shrink)
We will discuss a mathematical proof found in Wittgenstein’s Nachlass, a constructive version of Euler’s proof of the infinity of prime numbers. Although it does not amount to much, this proof allows us to see that Wittgenstein had at least some mathematical skills. At the very last, the proof shows that Wittgenstein was concerned with mathematical practice and it also gives further evidence in support of the claim that, after all, he held a constructivist stance, at least during the transitional (...) period of his thought (1929-33). (shrink)
In 1956, a series of BBC radio talks was published in London under the title The Revolution in Philosophy . This short book included papers by prominent British philosophers of the day, such as Sir Alfred Ayer and Sir Peter Strawson, with an introduction by Gilbert Ryle. Although there is precious little in it concerning the precise nature of the ‘revolution’ alluded to in the title, it is quite clear that these lectures were meant to celebrate in an insular manner (...) the birth of ‘analytic philosophy’ at the hands of Moore, Russell, and Wittgenstein. The use of the word ‘revolution’ to describe the birth of ‘analytical philosophy’ and its rise to near complete dominance in the British universities thus carries with it connotations of a forcible substitution of one philosophical order by a new one that itself owed nothing to the past. To me, however, this talk of ‘revolution’ carries with it a false view of the history of British philosophy: it isn’t ‘historical’ at all, just ideological; it was introduced for a strategic purpose, namely that of encouraging new generations of students to avoid reading the work of earlier philosophers or becoming interested in the problems that concerned them. I shall sketch the broad outlines of a landscape that involves, when limited to the specific topic of the theory of knowledge, no radical break, where no entirely new order replaces an older one: the options, so to speak, and even some of the arguments are the same before and after the soi-disant ‘revolution’. (shrink)
La thèse selon laquelle la signification d’un énoncé mathématique est donnée par sa preuve a été soutenue à la fois par Wittgenstein et par les intuitionnistes, à la suite de Heyting et de Dummett. Dans ce texte, nous nous attachons à clarifier le sens de cette thèse chez Wittgenstein, afin de montrer en quoi sa position se distingue de celle des intuitionnistes. Nous montrons par ailleurs que cette thèse prend sa source chez Wittgenstein dans sa réflexion, durant la période intermédiaire, (...) sur la notion de preuve par induction. Nous esquissons aussi les grandes lignes de la réponse que Wittgenstein fait à un certain nombre d’objections, dont celle selon laquelle cette thèse, dans le sens qu’il lui donne, remet en question la possibilité même de formuler une conjecture en mathématique. Nous terminons en montrant comment les propos de Wittgenstein trouvent un écho favorable dans le paradigme contemporain de la “proposition comme type” et les extensions de l’isomorphisme de Curry-Howard dont il est issu.The thesis according to which the meaning of a mathematical sentence is given by its proof was held by both Wittgenstein and the intuitionists, following Heyting and Dummett. In this paper, we clarify the meaning of this thesis for Wittgenstein, showing how his position differs from that of the intuitionists. We show how the thesis originates in his thoughts, from the middle period, about proofs by induction, and we sketch his answers to a number of objections, including the idea that, given the particular meaning he gives to this thesis, he cannot account for mathematical conjectures. We conclude by showing how his views find a favourable echo today in the paradigm of “proposition-as-type” and extensions of the Curry-Howard isomorphism from which this paradigm originates. (shrink)
Waismann’s writings can be divided into three periods. The fi rst corresponds to his early work in Vienna under the aegis of Schlick, thus mainly to his collaboration with Wittgenstein on the fi rst drafts of Logik, Sprache, Philosophie, out of which came not only the book itself many years later but also transcriptions of conversations with Schlick and Wittgenstein and numerous dictations reworked by Waismann, now published under the title The Voice of Wittgenstein. The Vienna Circle. Waismann also did (...) at that stage independent work, albeit largely infl uenced by Wittgenstein, on probability and identity. The second period runs roughly from the moment relations with Wittgenstein were severed – towards the end of 1934 – to his arrival in Oxford, where he started lecturing in Michaelmas Term 1939. (shrink)
Wittgenstein est mort en 1951 et on attend toujours une édition de ses œuvres complètes. Ce n'est qu'en 1994 que sont parus, accompagnés d'un volume d'introduction à l'ensemble du projet d'édition de la main du directeur de publication, Michael Nedo, les deux premiers d'une série de quinze volumes, les Wiener Ausgabe, qui reproduiront l'intégralité des écrits de Wittgenstein, de son retour à Cambridge en janvier 1929 à la première version du Big Typescript en 1933, avec index et concordances. D'après le (...) catalogue établi par Georg Henrik von Wright, il s'agit des articles suivants: MS 105 à 114 et 153 à 155, TS 208 à 218. Ces deux premiers volumes reproduisent les manuscrits écrits entre janvier ou février 1929 et l'été 1930, soit les MS 105, 106, 107 et 108. Ils constituent l'aboutissement d'une véritable saga entourant l'œuvre posthume de Wittgenstein, dont il vaut la peine de rapporter ici quelques-uns des faits marquants. (shrink)
Dans ce texte, je pars de l’analyse intuitionniste de la vérité mathématique, « A est vrai si et seulement s’il existe une preuve de A » comme cas particulier de l’analyse de la vérité en termes de « vérifacteur », et je montre pourquoi Wittgenstein partageait celle-ci avec les intuitionnistes. Cependant, la notion de preuve à l’oeuvre dans cette analyse est, selon l’intuitionnisme, celle de la « preuve-comme-objet », et je montre par la suite, en interprétant son argument sur le (...) caractère « synoptique » des preuves, que Wittgenstein avait plutôt en tête une conception de la « preuve-comme-trace ».In this paper, I start with the intutionist analysis of mathematical truth, « A is true if and only if there exists a proof of A », as a particular case of the analysis of truth in terms of « truth-makers », and I show why Wittgenstein shared it with the intuitionists. However, the notion of proof at work in this analysis is, according to intuitionism, that of « proof-as-object », and I then show, with an interpretation of his argument on the « surveyability » of proofs, that, instead, Wittgenstein had in mind a notion of « proof-as-trace ». (shrink)
L’opinion est souvent exprimée que Bradley fut un des tout premiers critiques du psychologisme. Dans cet article, j’examine cette thèse en me penchant principalement sur ses Principles of Logic . Je définis le psychologisme au sens étroit comme une thèse portant sur les fondements de la logique, et le psychologisme au sens large comme une thèse plus générale en théorie de la connaissance pour montrer que Bradley a rejeté les deux, même s’il n’avait pas grand chose à dire sur la (...) version étroite. Sa critique de l’autre version est basée sur une distinction entre contenu psychologique et contenu logique, et sur sa défense de la thèse de l’idéalité du contenu logique, avant Frege et Husserl. Cependant, il tient encore à l’idée que le contenu logique provient de la perception. Après une brève présentation de ses critiques de la psychologie associationniste, je montre qu’il fait face à de véritables difficultés en essayant d’éviter de retomber dans le psychologisme en faisant appel à la distinction entre universel abstrait et universel concret. Je termine avec quelques remarques sur la place de Bradley dans l’histoire de la psychologie britannique.One often hears the opinion voiced that Bradley was an early critique of psychologism. In this paper, I investigate that claim, focussing on his Principles of Logic . I define psychologism in the narrow sense as a thesis pertaining to the foundations of logic, and psychologism in the wide sense as a more general thesis concerning the theory of knowledge, and show that Bradley rejected both, although he had little to say on the narrow version. His criticism of the wider version is based on his distinguishing between psychological and logical content and on his defence of the ideality of logical content, before Frege and Husserl. Nevertheless, he still hung to the idea that the latter harks back to ordinary perception. I then review briefly his criticisms of associationism in psychology, to show that he faced some difficulties in trying to avoid lapsing back into psychologism, with an appeal to a distinction between abstract and concrete universals. I conclude with some remarks on the palace of Bradley in the history of British psychology. (shrink)
Reuben Louis Goodstein (1912-1985) foi aluno de Wittgenstein em Cambridge de 1931 a 1934. Neste artigo, faço uma breve descrição de seu trabalho na lógica matemática, no qual se percebe a influência das idéias de Wittgenstein, inclusive a substituição, em seu cálculo equacional, da indução matemática por uma regra de unicidade de uma função definida por uma função recursiva. Esse último aspecto se encontra no Big Typescript de Wittgenstein. Também mostro que as idéias fundamentais do cálculo equacional podem ser encontradas (...) não apenas no período intermediário, mas, in nuce, nas observações sobre matemática do Tractatus Logico-philosophicus. A partir disso, procuro desenvolver um argumento contra uma leitura corrente daquele livro, o assim chamado “Novo Wittgenstein”. Outra conexão entre Goodstein e Wittgenstein se encontra na rejeição da teoria da quantificação; na parte final do artigo, recorro às observações críticas de Goodstein sobre a Lei do Terceiro Excluído (que também incluem uma crítica a Brouwer e à sua rejeição “pela metade” dessa lei) para lançar luz sobre as observações do próprio Wittgenstein a esse respeito. (shrink)
L’idéalisme britannique est un mouvement qui a dominé les universités britanniques pendant une cinquantaine d’années à la fin du xixe siècle et au début du xxe siècle, mais qui est passé presque totalement inaperçu dans le monde francophone. Rejetés en bloc par les philosophes analytiques, ces auteurs ont aussi été ignorés pendant longtemps dans leur pays, mais certains d’entre eux, notamment Bradley et Collingwood, jouissent d’un regain d’intérêt à la faveur d’un renouveau des études sur les origines de la philosophie (...) analytique. Ce texte est une introduction à l’idéalisme britannique, qui retrace, dans une première partie plus historique, les grandes lignes de sa genèse, son développement et son déclin. Dans une deuxième partie, nous donnons quelques arguments en faveur d’une étude plus approfondie de ce mouvement.British Idealism is a philosophical movement that dominated British universities , for fifty years around the turn from the XIXth to the XXth century, but it went largely unnoticed in the French-speaking world. Condemned by analytic philosophers, these authors were also ignored in their own country, but some of them, notably Bradley and Collingwood, are now enjoying a newly found popularity within the larger trend towards a study of the origins of analytic philosophy. This text is an introduction to British Idealism that plots, in an historical first part, the outlines of its rise, development and decline. In the second part, we provide reasons for further studies of this movement. (shrink)
The idea of interpreting quantifiers in terms of a game between two players was first suggested at the end of the 19th century by one of the inventors of quantification theory, C. S. Peirce, but it laid buried in his papers until it was discovered in the 1980s. His idea was independently discovered in the 1950s, when Leon Henkin suggested a game semantics for infinitary languages. Paul Lorenzen introduced his Dialogspiele at the same time, while his student Kuno Lorenz introduced (...) the vocabulary of game theory that led to our modern conception of game semantics shortly after. The idea is to provide an explanation of the meaning of the logical connectives and quantifiers in terms of rules for non-collaborative, zero-sum games between two agents, one of whom argues for the validity of the claim against moves from the other, and to define truth in terms of the existence of a winning strategy for the defender. (shrink)
Après avoir présenté les grandes lignes de la réflexion phénoménologique de Wittgenstein en 1929 et son abandon de Vidée d'un langage phénoménologique, je montre qu'il fait face à un dilemme à propos de la notion de règle. Si on regarde l'expression symbolique d'une règle sous le mode physicaliste, on ne peut pas voir le lien entre celle-ci et ses applications. Comment peut-elle, de par elle-même, servir de guide à nos actions ? Il faut une intention, une interprétation, ce qui fait (...) de la règle un objet phénoménologique. L'abandon du langage phénoménologique doit cependant forcer Wittgenstein à reconnaître qu'une règle en tant qu'objet phénoménologique ne peut pas être comparée à ou être utilisée pour déclencher une action qui se déroule dans le monde physique. Je montre que c'est en tentant de sortir de ce dilemme que Wittgenstein en viendra aux conceptions exposées dans ses remarques sur « suivre une règle ». J'examine en dernier lieu quelques conséquences de cette interprétation sur celle de la philosophie des mathématiques de Wittgenstein.After presenting a broad sketch of Wittgenstein's phenomenology; in 1929, and of his abandonment of the idea of a phenomenological language, it is shown that the notion of a rule left him with a dilemma, if the symbolical expression of a rule is understood in a physicalist mode, one cannot see the link between it and its applications. How could it, of itself guide our actions? One needs an intention or interpretation, thus turning the rule into a phenomeno/ogica I object. The abandonment ofthe p he nojne no logical language must have foiled Wittgenstein to recognize that a rule, qua phenomenological object, cannot be compared to or used to trigger an action in the physical world. It is then shown how Wittgenstein reached, while trying to solve this dilemma, the conception of rules presented in the remarks on 'following a rule". Lastly, some of the consequences of this new reading on the interpretation of Wittgenstein's philosophy of mathematics are examined. (shrink)
In 1956, a series of BBC radio talks was published in London under the title The Revolution in Philosophy. This short book included papers by prominent British philosophers of the day, such as Sir Alfred Ayer and Sir Peter Strawson, with an introduction by Gilbert Ryle. Although there is precious little in it concerning the precise nature of the ‘revolution’ alluded to in the title, it is quite clear that these lectures were meant to celebrate in an insular manner the (...) birth of ‘analytic philosophy’ at the hands of Moore, Russell, and Wittgenstein. The use of the word ‘revolution’ to describe the birth of ‘analytical philosophy’ and its rise to near complete dominance in the British universities thus carries with it connotations of a forcible substitution of one philosophical order by a new one that itself owed nothing to the past. To me, however, this talk of ‘revolution’ carries with it a false view of the history of British philosophy: it isn’t ‘historical’ at all, just ideological; it was introduced for a strategic purpose, namely that of encouraging new generations of students to avoid reading the work of earlier philosophers or becoming interested in the problems that concerned them. I shall sketch the broad outlines of a landscape that involves, when limited to the specific topic of the theory of knowledge, no radical break, where no entirely new order replaces an older one: the options, so to speak, and even some of the arguments are the same before and after the soi-distant ‘revolution’. (shrink)