This is the first book-length treatment of hybrid logic and its proof-theory. Hybrid logic is an extension of ordinary modal logic which allows explicit reference to individual points in a model (where the points represent times, possible worlds, states in a computer, or something else). This is useful for many applications, for example when reasoning about time one often wants to formulate a series of statements about what happens at specific times. There is little consensus about proof-theory for ordinary modal logic. Many modal-logical proof systems lack important properties and the relationships between proof systems for different modal logics are often unclear. In the present book we demonstrate that hybrid-logical proof-theory remedies these deficiencies by giving a spectrum of well-behaved proof systems (natural deduction, Gentzen, tableau, and axiom systems) for a spectrum of different hybrid logics (propositional, first-order, intensional first-order, and intuitionistic).

This book presents logical foundations of dual tableaux together with a number of their applications both to logics traditionally dealt with in mathematics and philosophy (such as modal, intuitionistic, relevant, and many-valued logics) and to various applied theories of computational logic (such as temporal reasoning, spatial reasoning, fuzzy-set-based reasoning, rough-set-based reasoning, order-of magnitude reasoning, reasoning about programs, threshold logics, logics of conditional decisions). The distinguishing feature of most of these applications is that the corresponding dual tableaux are built in a relational language which provides useful means of presentation of the theories. In this way modularity of dual tableaux is ensured. We do not need to develop and implement each dual tableau from scratch, we should only extend the relational core common to many theories with the rules specific for a particular theory.

This systematic and historical treatment of Russell's contributions to analytic philosophy, from his embrace of analysis in 1898 to his landmark theory of descriptions in 1905, draws important connections between his philosophically motivated conception of analysis and the technical apparatus he devised to facilitate analyses in mathematics

Lambda Calculi: A Guide Interpolation and Definability Discourse Representation Theory

The book is about Gentzen calculi for (the main systems of) modal logic. It is divided into three parts. In the first partwe introduce and discuss the main philosophical ideas related to proof theory, and we try to identify criteria for distinguishing good sequent calculi. In the second part we present the several attempts made from the 50's until today to provide modal logic with Gentzen calculi. In the third and and final part we analyse new calculi for modal logics, called tree-hypersequent calculi, which were recently introduced by the author. We show in a precise and clear way the main results that can be proved with and about them.

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While probabilistic logics in principle might be applied to solve a range of problems, in practice they are rarely applied - perhaps because they seem disparate, complicated, and computationally intractable. This programmatic book argues that several approaches to probabilistic logic fit into a simple unifying framework in which logically complex evidence is used to associate probability intervals or probabilities with sentences. Specifically, Part I shows that there is a natural way to present a question posed in probabilistic logic, and that various inferential procedures provide semantics for that question, while Part II shows that there is the potential to develop computationally feasible methods to mesh with this framework. The book is intended for researchers in philosophy, logic, computer science and statistics. A familiarity with mathematical concepts and notation is presumed, but no advanced knowledge of logic or probability theory is required.

The book explains why and how Wittgenstein adapted the Tractatus in phenomenological and grammatical terms to meet challenges of his 'middle period.' It also shows why and how he invents a new method and develops an anthropological perspective, which gradually frame his philosophy and give birth to the Philosophical Investigations .

Kierkegaard and Nietzsche revive an ancient approach to ethics that evaluates different ways of life considered as a whole. Comparing and contrasting their respective ideals of faith and individual sovereignty, this work reveals a valuable new path for contemporary ethics.

In this book, Livingston develops the political implications of formal results obtained over the course of the twentieth century in set theory, metalogic, and computational theory. He argues that the results achieved by thinkers such as Cantor, Russell, Godel, Turing, and Cohen, even when they suggest inherent paradoxes and limitations to the structuring capacities of language or symbolic thought, have far-reaching implications for understanding the nature of political communities and their development and transformation. Alain Badiou's analysis of logical-mathematical structures forms the backbone of his comprehensive and provocative theory of ontology, politics, and the possibilities of radical change. Through interpretive readings of Badiou's work as well as the texts of Giorgio Agamben, Jacques Lacan, Jacques Derrida, Gilles Deleuze, and Ludwig Wittgenstein, Livingston develops a formally based taxonomy of critical positions on the nature and structure of political communities. These readings, along with readings of Parmenides and Plato, show how the formal results can transfigure two interrelated and ancient problems of the One and the Many: the problem of the relationship of a Form or Idea to the many of its participants, and the problem of the relationship of a social whole to its many constituents.

Logic as Universal Science offers a detailed reconstruction of the underlying philosophy in The Principles of Mathematics showing how Russell sought to deliver a death blow to the dominant Kantian view that formal logic is a concise and dry science and unable to enlarge our understanding.

The book offers a novel approach to the idea of divinity in guise of a philosophical doctrine called 'Logical Pantheism', according to which the only way to establish the existence of God undeniably is by equating God with Logical Space.

A COMPANION TO WITTGENSTEIN The most comprehensive survey of Wittgenstein's thought yet compiled, this volume of fifty newly commissioned essays by leading interpreters of his philosophy is a keynote addition to the Blackwell Companions to Philosophy series. Full of penetrating insights into the life and work of the most important philosopher of the twentieth century, the collection explores the full range of Wittgenstein's contribution to philosophy. It includes essays on his intellectual development, his work in logic and mathematics, philosophy of language, philosophy of mind and action, epistemology, ethics, philosophy of religion, and much else. As well as examining Wittgenstein's contribution to human understanding in detail, the Companion features vital contextual analysis that traces the relationship between his ideas and those of other philosophers and schools of thought, including the Aristotelian and continental philosophical traditions. Authors also address prominent themes that remain current in today's philosophical debates, explaining Wittgenstein's continuing legacy alongside his historical significance. Essential reading for scholars of philosophy at all levels, A Companion to Wittgenstein combines engaging commentary with unrivaled academic authority.

Action is conceived of as an intentional behavior of an individual or of an institutional subject; it is determined by information processing, namely by a process in which pieces of descriptive and practical information are involved. Action is explained by a formal and finalistic theory which is connected with a specific theory of institutions. The philosophical basis of the logic of norm sentences and of other systems of practical thinking (formal teleology, axiology, logic of preferences) is discussed. The author criticizes traditional deontic logic and argues in favor of a genuine logic of norms. The book gives a structure analysis of the so-called practical inference and of nomic causal propositions. Besides a critical account of von Wright's practical philosophy the author offers critical analyses of discourse rationality (Habermas, Apel, Alexy) and of Wittgenstein's views on philosophizing. The book addresses readers interested in philosophical logic, practical philosophy, sociology of institutions, legal philosophy, and theory democracy.

This work is in two parts. It began as a general investigation of vagueness in natural languages. The Sorites Paradox came to dominate the work however, and the second part of the book consists in an discussion ofthat puzzle and related problems. The first part contains a general discussion ofthe nature ofvagueness and its sources. I discuss various conceptions of vagueness in chapter 1 and outline some of the problems to do with the conception of vagueness as a linguistic phenomenon. The most interesting of these is the Sorites paradox, which occurs where natural languages exhibit a particular variety of borderline case vagueness. I discuss some sources of vagueness of the borderline case variety, and views of the relation between linguistic behaviour and languages which are vague in this sense. I argue in chapter 2 that these problems are not to be easily avoided by statistical averaging techniques or attempts to provide a mathematical model of consensus in linguistic usage. I also consider in chapter 3 various approaches to the problem of providing an adequate logic and semantics for vague natural languages, and argue against two currently popular approaches to vagueness. These are supervaluation accounts which attempt to provide precise semantic models for vague languages based on the notion of specification spaces, and attempts to replace the laws ofclassical logic with systems offuzzy logic.

Kawalec's monograph is a novel defence of the programme of inductive logic, developed initially by Rudolf Carnap in the 1950s and Jaakko Hintikka in the 1960s. It revives inductive logic by bringing out the underlying epistemology. The main strength of the work is its link between inductive logic and contemporary discussions of epistemology. Through this perspective the author succeeds to shed new light on the significance of inductive logic. The resulting structural reliabilist theory propounds the view that justification supervenes on syntactic and semantic properties of sentences as justification-bearers. The claim is made that this sets up a genuine alternative to the prevailing theories of justification. Kawalec substantiates this claim by confronting structural reliabilism with a number of epistemological problems. Therefore, the book is interesting for philosophers of science dealing with problems of induction, but it will also appeal to readers working in the theory of knowledge. Kawalec writes in a clear manner, makes his theses and arguments explicit, and gives ample bibliographical references. The book will be a valuable companion to graduate and postgraduate courses on inductive logic.

All except three of the papers in this volume were presented at the colloquium on "L'Ontologie formelle aujourd'hui," Geneva, 3-5 June 1988. The three exceptions, the papers by David Armstrong, Uwe Meixner and Wolfgang Lenzen, were presented at the colloquium on "Properties," Zinal, June 1-3, 1990. It was, incidentally, at the second of these two colloquia that the European Society for Analytic Philosophy came into being. The fathers of analytic philosophy - Moore and Russell - were in no doubt that ontology or metaphysics as well as the topics oflanguage, truth and logic constituted the core subject-matter of their "analytic realism," 1 for the task of metaphysics as they conceived things was the description of 2 the world. And logic and ontology are indissolubly linked in the system of the grandfather of analytic philosophy, Frege. After the Golden Age of analytic philosophy - in Cambridge and Austria - opposition to realism as well as the "linguistic turn" contributed for a long time to the eclipse of ontology. 3 Thanks in large measure to the work of some of the senior contributors to the present volume - Roderick Chisholm, Herbert Hochberg, David Armstrong and Karel Lambert - ontology and metaphysics now enjoy once again the central position they occupied some eighty years ago in the heyday of analytic philosophy.

Non-Classical Logics and their Applications to Fuzzy Subsets is the first major work devoted to a careful study of various relations between non-classical logics and fuzzy sets. This volume is indispensable for all those who are interested in a deeper understanding of the mathematical foundations of fuzzy set theory, particularly in intuitionistic logic, Lukasiewicz logic, monoidal logic, fuzzy logic and topos-like categories. The tutorial nature of the longer chapters, the comprehensive bibliography and index make it suitable as a valuable and important reference for graduate students as well as research workers in the field of non-classical logics. The book is arranged in three parts: Part A presents the most recent developments in the theory of Heyting algebras, MV-algebras, quantales and GL-monoids. Part B gives a coherent and current account of topos-like categories for fuzzy set theory based on Heyting algebra valued sets, quantal sets of M-valued sets. Part C addresses general aspects of non-classical logics including epistemological problems as well as recursive properties of fuzzy logic.

Legal statements are, according to the authors, the most basic elements of the law. Nevertheless they must be considered not only as the pieces of a puzzle, but also as the components of a dynamic and highly complex reality: the law of contemporary society. The book presents an analysis of the different types of legal statements (mandatory rules, principles, power-conferring rules, definitions, permissions, values and the rule of recognition) from a threeefold perspective, that is, considering their logical structure, their function in legal reasoning as reasons for action, and their connections with the interests and power relationships among the individuals and the social groups. The result is conceived as a first step in the building of a general theory of law designed not as an isolated discourse but as a decisive element for the dynamization of the legal culture.

The task of the book is not to give a survey of the main theories on truth found in the literature. There are several books available which do this: The one of David for Deflationist (and Disquotational) Theories of Truth; that of Chapuis for Revision Theories of Truth; that of Kirkham for Correspondence Theories and several others; that ofRescher for Coherence Theories of Truth. Moreover the book is not an analy sis just of Tar ski's theory, like that of Moreno or the respective chapters in Kirkham, though Tarski's theory plays an important role in the whole work presented. The task of the book is to give a detailed answer to some basic questions on truth which have been perennial problems through the centuries and are still discussed today. The answer is given in the light of our knowledge today and with the help of modem logic. But the book explicitly aims at connecting recent problems with re lated ones in the whole history of philosophy. The method to incorporate important philosophers of the tradition into the analysis is that of disputation, i. e. of putting some of their main thesis into objections or counterobjections pro or contra a posi tive answer to the respective question. After the pros and cons are given a detailed answer to the question is proposed and finally commentaries and corrections are given to the objections and counterobjections in the light of the proposed answer.

Belief change is an emerging field of artificial intelligence and information science dedicated to the dynamics of information and the present book provides a state-of-the-art picture of its formal foundations. It deals with the addition, deletion and combination of pieces of information and, more generally, with the revision, updating and fusion of knowledge bases. The book offers an extensive coverage of, and seeks to reconcile, two traditions in the kinematics of belief that often ignore each other - the symbolic and the numerical (often probabilistic) approaches. Moreover, the work encompasses both revision and fusion problems, even though these two are also commonly investigated by different communities. Finally, the book presents the numerical view of belief change, beyond the probabilistic framework, covering such approaches as possibility theory, belief functions and convex gambles. The work thus presents a unified view of belief change operators, drawing from a widely scattered literature embracing philosophical logic, artificial intelligence, uncertainty modelling and database systems. The material is a clearly organised guide to the literature on the dynamics of epistemic states, knowledge bases and uncertain information, suitable for scholars and graduate students familiar with applied logic, knowledge representation and uncertain reasoning.

th This volume is dedicated to Dov Gabbay who celebrated his 50 birthday in October 1995. Dov is one of the most outstanding and most productive researchers we have ever met. He has exerted a profound influence in major fields of logic, linguistics and computer science. His contributions in the areas of logic, language and reasoning are so numerous that a comprehensive survey would already fill half of this book. Instead of summarizing his work we decided to let him speak for himself. Sitting in a car on the way to Amsterdam airport he gave an interview to Jelle Gerbrandy and Anne-Marie Mineur. This recorded conversation with him, which is included gives a deep insight into his motivations and into his view of the world, the Almighty and, of course, the role of logic. In addition, this volume contains a partially annotated bibliography of his main papers and books. The length of the bibliography and the broadness of the topics covered there speaks for itself.

This volume consists of papers delivered at the conference 'The Lvov-Warsaw School and Contemporary Philosophy', organised in celebration of the hun- dredth anniversary ofKazimierz Twardowski's first lecture as Professor of Phi- losophy at Lvov University. This lecture can be regarded as the starting point of the development of analytic philosophy in Poland, which culminated in the Warsaw School of Logic. The conference was held in Lvov (15-17 November) and Warsaw (19-21 November 1995). It was organised jointly by the Ukrainian Academy of Sci- ences and the Polish Academy of Sciences. The general organisation was un- dertaken by Professor Andrzej Grzegorczyk (polish Academy of Sciences) and Professor Marat Vernikov (Ukrainian Academy of Sciences). Professors Jaroslaw Isaievich (Ukrainian Academy of Sciences) and Jan Wolenski (Jagiel- Ionian University) were responsible for the scientific programme. Over 100 philosophers participated in the conference. Papers published in this volume are organised according to the sections of the conference and rep- of the papers delivered. resent a selection The editors would like to express their gratitude to Professor Andrzej Grze- gorczyk, spiritus movens of the conference, who, by including the present vol- ume in a programme of publications connected with the hundredth anniversary of the Lvov-Warsaw School, provided financial support for its preparation. Fi- nally, we express our gratitude to Dr Timothy Childers of the Academy of Sciences of the Czech Republic for correcting the English of the papers.

In the Preliminary Dissertation' of his Theodicy, Leibniz declares himself an apologist for the compatibilist doctrines of original sin, election and reprobation propounded by the theologians of the Augsburg Confession. According to those theologians, man's actions are determined but man retains the power to act otherwise and therefore is responsible for his actions. Savage argues that Leibniz, in formulating his apology, availed himself of both his doctrine of possible worlds and his finite-infinite analysis distinction (the latter being applied within the former). Savage challenges the dogma that Leibniz's metaphysical principles entail that individuals are powerless to act otherwise and that God cannot conceive of them acting otherwise. He argues that interpreters deduce the dogma from those principles with the aid of dubious extra-textual premises, for example, that a Leibnizian individual has only one complete concept or cannot be persons other than the person it actually is.

Scholars from all the continents have written articles to celebrate the seventieth birthday of Jan Srzednicki, a thinker still at the height of his powers. Srzednicki's scientific work alternates between problems of Austrian and German philosophy and questions of political philosophy. The papers published in this volume discuss topics of general philosophy, in the clear and deep style both of Srzednicki's own philosophical work and of the authors investigated in his writings (mainly Brentano and the Polish tradition of analytic philosophy). The topics developed pertain to the fields of epistemology (common sense, knowledge and objectivity, truth and perception) and of logic and philosophy of logic (paraconsistent logic, definition and duality).

The present volume has its origin in a meeting of philosophers, linguists and cognitive scientists that was held at Umea University, Sweden, September 24-26, 1993. The meeting was organized by the Department of Philosophy in cooperation with the Department of Linguistics, and it was called UmLLI-93, the Umea Colloquium on Dynamic Approaches in Logic, Language and Information. The papers published here are considerably expanded and revised versions of talks presented by invited speakers at this colloquium. The papers included here fall into three broad categories. In the first part of the book, Action, we have collected papers that concern the formal theory of action, the logic of nonns, and the theory of rational decision. The papers in the second part, Belief Change, concern the theory of belief dynamics in the tradition of Alchourr6n, Gardenfors and Makinson. The third part, Cognition, concerns abstract questions about knowledge and truth as well'as more concrete questions about the usefuleness and tractability of various graphic representations of infonnation. An additional and important topic of the colloquium concerned logical approaches to natural language. For the sake of the thematic unity of this book, and its appearance in the series Trends in logic, the colloquium papers related to language are not included here, but some of these contributions will appear in the philosophical journal Theoria.