Constantes logiques et décision

Dans cet article, j'analyse le problème des significations des constantes logiques. Ces significations sont-elles fixées conventionnellement comme le suggèrent Carnap et Wittgenstein, ou bien doivent-elles s'imposer à tous et ne pas dépendre de décisions préalables ? Après avoir examiné le conventionnalisme de Wittgenstein et Carnap et l'anti-conventionnalisme de Peacocke selon lequel les sens des constantes logiques reposent sur des conceptions implicites, je montre que les deux thèses sont également critiquables. La première ne résiste pas à l'incohérence du connecteur « tonk », inventé par Prior, dont les règles montrent que la convention ne peut pas déterminer à elle seule les significations des constantes logiques, la deuxième ne tient pas assez compte des divergences importantes entre les logiques. En me basant sur différents systèmes logiques, je présente de nouveaux arguments pour défendre une position intermédiaire selon laquelle chaque constante logique se déploie en diverses variantes qui forment un spectre allant de la version la plus forte à la version la plus faible. Dans ce cadre, le concept de décision joue un rôle en logique, mais les décisions sont prises en amont, en fonction de certaines conceptions touchant la vérité, la déduction et les critères de logicité adoptés par les logiciens, et tiennent compte des intuitions fondamentales liéesà chaque constante.In this article, I examine the problem of the meanings of the logical constants. Are these meanings conventional as suggested by Carnap and Wittgenstein, or should we say that they are assigned and do not depend on preliminary decisions? After studying the conventionalism defended by Wittgenstein and Carnap and the anti-conventionnalism endorsed by Peacocke, according to which the meanings of the logical constants depend on some implicit conceptions, I show that both theses can equally be criticized. The first one does not resist the incoherence of the connective “tonk” invented par Prior, whose rules show that the convention cannot by itself fix the meanings of the logical constants, the second does not take sufficient account of the important differences between the logical systems. By relying on different logical systems, I give some new arguments to defend an intermediary position according to which each logical constant has different variants which go from the strongest version to the weakest one. In this context, the concept of decision plays a role in logic but the decisions depend on some previous fundamental conceptions with regard to truth, deduction and the criteria of logicality which are endorsed by the logicians, and they take into account the fundamental intuitions related to each constant

The Semantics and Pragmatics of the Conditional in al-Fārābī’s and Avicenna’s Theories

In this paper, I examine al-Fārābī's and Avicenna's conceptions of the conditional. I show that there are significant differences between the two frames, despite their closeness. Al-Fārābī distinguishes between an accidental conditional and two “essential” conditionals. The accidental conditional can occur only once and pragmatically involves succession. In the first “essential” conditional, the consequent follows regularly the antecedent; pragmatically it involves likeliness. The second “essential” conditional can be either complete or incomplete. Semantically the former means “if and only if”; pragmatically it means “necessarily if and only if”. The latter is expressed by ‘if, then’ and means entailment; pragmatically, it involves necessity and the inclusion of the antecedent into the consequent. As to Avicenna, he rejects explicitly al-Fārābī’s complete conditional and distinguishes between the luzūm (real implication) and what he calls ittifāq. He quantifies over situations (or times) to express the various conditionals. The two universals AC and EC are expressed by “In all situations, if…, then…”, while the two particulars IC and OC are expressed by “In some situations, if…, then..”. This gives them a modal connotation, and makes the universals close to strict implications. Pragmatically, AC presupposes the truth of the antecedent, but there is no such presupposition in EC, while what is presupposed in both IC and OC is a (possible) conjunction

Arabic logic from al-Fārābī to Averroes: a study of the early Arabic categorical, modal, and hypothetical syllogistics

This monograph explores the logical systems of early logicians in the Arabic tradition from a theoretical perspective, providing a complete panorama of early Arabic logic and centering it within an expansive historical context. By thoroughly examining the writings of the first Arabic logicians, al-Fārābī, Avicenna and Averroes, the author analyzes their respective theories, discusses their relationship to the syllogistics of Aristotle and his followers, and measures their influence on later logical systems. Beginning with an introduction to the writings of the most prominent Arabic logicians, the author scrutinizes these works to determine their categorical logic, as well as their modal and hypothetical logics. Where most other studies written on this subject focus on the Arabic logicians’ epistemology, metaphysics, and theology, this volume takes a unique approach by focusing on the actual technical aspects and features of their logics. The author then moves on to examine the original texts as closely as possible and employs the symbolism of modern propositional, predicate, and modal logics, rendering the arguments of each logician clearly and precisely while clarifying the theories themselves in order to determine the differences between the Arabic logicians’ systems and those of Aristotle. By providing a detailed examination of theories that are still not very well-known in Western countries, the author is able to assess the improvements that can be found in the Arabic writings, and to situate Arabic logic within the breadth of the history of logic. This unique study will appeal mainly to historians of logic, logicians, and philosophers who seek a better understanding of the Arabic tradition. It also will be of interest to modern logicians who wish to delve into the historical aspects and progression of their discipline. Furthermore, this book will serve as a valuable resource for graduate students who wish to complement their general knowledge of Arabic culture, logic, and sciences

Logic and Philosophy of Science in Nancy (II)

This issue collects a selection of contributed papers presented at the 14th International Congress of Logic, Methodology and Philosophy of Science in Nancy, July 2011. These papers were originally presented within two of the main sections of the Congress. They deal with general philosophy of science (including ethical and historical aspects of philosophy of science), and philosophy of biology, physics, chemistry and economics. A first volume of contributed papers, dedicated to logic, philosophy of mathematics and cognitive science, and philosophy of technology, appeared in the last issue of Philosophia Scientiæ (18-3), 2014