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Die überwiegende Zahl der Begriffe in natürlichen Sprachen verfügt über unscharfe Begriffsumfänge. Sie lassen Grenzfälle zu, d.h. es gibt Gegenstände, für die nicht ohne Weiteres feststeht, ob sie unter den jeweiligen Begriff fallen oder nicht. Wo geht zum Beispiel Rot in Orange über? Solche Begriffe sind vage. Sie können zu logischen Problem führen, da die Sätze, die sie enthalten, oft nicht eindeutig als wahr oder falsch bewertet werden können. Vagheit wird darum meist als Defekt natürlicher Sprachen betrachtet. Doch die Vagheit in den natürlichen Sprachen hat auch Vorteile, die in dieser Arbeit aufgezeigt werden: Die Kommunikation mit vagen Prädikaten ist trotz aller formallogischen Probleme in der Regel erfolgreich. Durch sie ist eine effiziente, ökonomische und flexible Kommunikation möglich. Vage Prädikate tragen zudem den limitierten kognitiven Ressourcen und Wahrnehmungsfähigkeiten des Menschen Rechnung. Die Arbeit untersucht zudem, ob Vagheit im Recht positive Aspekte hat, und analysiert alltagspraktische Anknüpfungspunkte.

We are happy to present to the reader the first book of our Applied Logic Series. Walton's book on the fallacies of ambiguity is firmly at the heart of practical reasoning, an important part of applied logic. There is an increasing interest in artifIcial intelligence, philosophy, psychol­ ogy, software engineering and linguistics, in the analysis and possible mechanisation of human practical reasoning. Continuing the ancient quest that began with Aristotle, computer scientists, logicians, philosophers and linguists are vigorously seeking to deepen our understanding of human reasoning and argumentation. Significant communities of researchers are actively engaged in developing new approaches to logic and argumentation, which are better suited to the urgent needs of today's applications. The author of this book has, over many years, made significant contributions to the detailed analysis of practical reasoning case studies, thus providing solid foundations for new and more applicable formal logical systems. We welcome Doug Walton's new book to our series.

Semantic underspecification is an essential and pervasive property of natural language. This monograph provides a comprehensive survey of the various phenomena in the field of ambiguity and vagueness. The book discusses the major theories of semantic indefiniteness, which have been proposed in linguistics, philosophy and computer science. It argues for a view of indefiniteness as the potential for further contextual specification, and proposes a unified logical treatment of indefiniteness on this basis. The inherent inconsistency of natural language induced by irreducible imprecision is investigated, and treated in terms of a dynamic extension of the proposed logic. The book is an extended edition of a German monograph and is addressed to advanced students and researchers in theoretical and computational linguistics, logic, philosophy of language, and NL- oriented AI. Although it makes extensive use of logical formalisms, it requires only some basic familiarity with standard predicate logic concepts since all technical terms are carefully explained.

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.

The essays in this book deal with a number of problems in the analysis of intensional language - more especially with the analysis of the personal modalities in natural language. Together they cover a representative spectrum of the problems of contemporary,interest in this area, in a way that should make them of interest to linguists, logicians and philosophers concerned with natural language. The contributors are mostly more linguists than logicians or philosophers but some are more logicians or philosophers than linguists. As far as possible, we have tried to conduct the discussion in terms that will enable students from any of these fields to come to grips with the central issues. This volume will provide, I think, material for a very stimulating course. I have used it as the basis for a course at the introductory level in the philosophy of language. The essays in the book led us back to look at the classic texts­ and a good deal of the intervening literature crept in of its own accord. Out of that experience grew the introduction that follows. In contrast with the rest of the book, the introduction is frankly pedagogical. I hope and believe that many who would otherwise find the papers themselves hard to digest will ~e helped on their way by that summary.

This volume brings together twelve papers by linguists and philosophers contributing novel empirical and formal considerations to theorizing about vagueness. Three main issues are addressed: gradable expressions and comparison, the semantics of degree adverbs and intensifiers (such as'clearly'), and ways of evading the sorites paradox.