Not Exactly: In Praise of Vagueness

by Kees van Deemter

Overview

Not everything is black and white. Our daily lives are full of vagueness or fuzziness. Language is the most obvious example - for instance, when we describe someone as tall, it is as though there is a particular height beyond which a person can be considered 'tall'. Likewise the terms 'blond' or 'overweight' in common usage. We often think in discontinuous categories when we are considering something continuous. In this book, van Deemter cuts across various disciplines in considering the nature and importance of vagueness. He looks at the principles of measurement, and how we choose categories; the vagueness lurking behind what seems at first sight crisp concepts such as that of the biological 'species'; uncertainties in grammar and the impact of vagueness on the programmes of Chomsky and Montague; vagueness and mathematical logic; computers, vague descriptions, and Natural Language Generation in AI (a new class of programs will allow computers to handle descriptions such as 'the man in the yellow shirt'). Van Deemter shows why vagueness is in various circumstances both unavoidable and useful, and how we are increasingly able to handle fuzziness in mathematical logic and computer science.

Product Details

ISBN-13:	9780191647857
Publisher:	OUP Oxford
Publication date:	01/28/2010
Sold by:	Barnes & Noble
Format:	eBook
Sales rank:	224,945
File size:	18 MB
Note:	This product may take a few minutes to download.

About the Author

Kees van Deemter is a Reader in Computing Science at the University of Aberdeen. He works in computational linguistics, the area of artificial intelligence where computer science meets linguistics and his main areas of expertise are computational semantics and natural language generation. He has previously authored 90 research publications in philosophical logic, artificial intelligence and computational linguistics.

Table of Contents

List of Figures xv

Prologue 1

1 Introduction: False Clarity 4

Vagueness 8

Paradox 10

Academic perspectives on vagueness 13

Part I Vagueness, Where One Least Expects It

2 Sex and Similarity: On the Fiction of Species 19

What is a species? 20

The Ensatina salamander 22

Lessons learned 27

3 Measurements that Matter 31

A short history of the metre 32

Obesity 36

Poverty 40

Intelligence 44

Dialogue intermezzo: After the job interviews 47

Scientific discovery and word meaning 51

4 Identity and Gradual Change 54

Identity: The case of Old Number One 54

Multiplying objects 57

Dialogue intermezzo: On Old Number One 59

What makes a book? 61

What makes a person? 62

What is a language? 64

Digression: Protection against change 65

So what? 68

5 Vagueness in Numbers and Maths 70

Vagueness in mathematics 71

Talking about numbers 77

Which computer program is fastest? 81

Statistical significance 84

Part II Theories of Vagueness

6 The Linguistics of Vagueness 93

Chomsky's machine: Computing grammaticality 93

Montague's machine: Computing meaning 95

The role of language corpora 101

Vague adjectives 103

The meaning of adjectives 105

Vagueness and ambiguity 110

Lack of specificity 115

Prototypes 117

Comparatives 119

Packaging what we say: Hedging 120

Future work 123

7 Reasoning with Vague Information 126

Reasoning with vague concepts 127

The sorites paradox 134

Vagueness as ignorance 138

Similarity is in the eye of the beholder: The case of colour 141

Dialogue intermezzo: On vagueness as ignorance 145

Continuity and vagueness 149

8 Parrying a Paradox 154

Logic and paradox 154

A crash course in classical logic 156

First deviation: Supervaluations and partial logic 161

Second deviation: Context-aware reasoning 167

Third deviation: Introspective agents 179

9 Degrees of Truth 187

Fuzzy logic 189

Dialogue intermezzo: On fuzzy logic 196

Fuzzy logic and the sorites paradox 200

Probabilistic versions of many-valued logic 203

What's wrong with degrees? 213

Part III Working Models of Vagueness

10 Artificial Intelligence 221

A brief history of AI 221

Artificial intelligence? 225

Qualitative reasoning 227

Applying fuzzy logic: An artificial doctor 229

The future of AI 233

11 When to be Vague: Computers as Authors 236

Example: Generating vague descriptions 241

Dialogue intermezzo: What use is a theory? 248

Tolerance revisited 251

A game theory perspective 252

Vagueness in the absence of conflict 261

Why do we speak? 271

12 The Expulsion from Boole's Paradise 277

Earlier questions revisited 277

Coping with vagueness 284

Epilogue: Guaranteed Correct 289

Notes 293

Recommended Reading 315

References 319

Index 333

Editorial Reviews

No one knows how many hairs you need to avoid baldness, nor when your growing dog becomes "big." "Vagueness" to van Deemter denotes, mostly, boundary problems. Baldness and bigness imply a range and can be dealt with in terms of probabilities. Colors are a bit trickier. Though different people see colors differently, color talk is useful. If this reviewer were to say, "Go out and bring in the purple cows," you may not see any purple cows, but odds are you will bring in the ones you don't see as black, grey, or white, and I will get my purple cows. Van Deemter argues that without such "vague" notions life would be more difficult. Vagueness can be tackled. "Fuzzy logic," which is not fuzzy at all but a system that picks out things within a range, helps. One can refine assaults on vagueness with many valued logics—which van Deemter likes—but that lands one in troublesome notions like "degrees of truth." Van Deemter does not ask about vague things, because those would defeat his theories. VERDICT A clever book, a bit smart-alecky but readable. Readers with technical interests in the issues might like Nicholas J. Smith's Vagueness and Degrees of Truth; lay readers who want to dig deeper into the weakness of traditional logics should still turn to Stephen Toulmin'sThe Uses of Argument.—Leslie Armour, Dominican Univ. Coll., Ottawa, Ont.

Library Journal