Gary Kemp

London and New York

First published 2002 by Routledge

11 New Fetter Lane, London EC4P 4EE Simultaneously published in the USA and Canada by Routledge

29 West 35th Street, New York, NY 10001 Routledge is an imprint of the Taylor & Francis Group This edition published in the Taylor & Francis e-Library, 2001. © 2002 Tracy Bowell and Gary Kemp

All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers.

British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data Bowell, Tracy, 1965-

Critical thinking: a concise guide/Tracy Bowell & Gary Kemp.

p. cm. Includes index.

ISBN 0-415-24016-6 (alk. paper) - ISBN 0-415-24017-4 (pbk.: alk. paper) 1. Critical thinking. I. Kemp, Gary, 1960 Oct. 15- II. Title B809.2 .B69 2001

160-dc21 2001031914

ISBN 0^15-24016-6 (hbk) ISBN 0^15-24017-1 (pbk) ISBN 0-203- 19375-X Master e-book ISBN ISBN 0-203-19378-4 (Glassbook Format)

Contents

Preface vii

Introduction and preview ix

Chapter 1 : Why should we become critical thinkers? 1

Beginning to think critically: recognising arguments • Identifying conclusions and premises • Intermediate conclusions • Linguistic phenomena

Chapter 2: Logic: deductive validity 42

The Principle of Charity • Truth • Deductive validity • Conditional propositions • Deductive soundness

Chapter 3: Logic: inductive force 69

Inductive force • 'All', 'most' and 'some' • Inductive soundness

• Probability in the premises • Arguments with multiple probabilistic premises • Inductive force in extended arguments

• Conditional probability in the conclusion • Evidence • Inductive inferences • A programme for assessment

Chapter 4: Rhetorical ploys and fallacies 99

Rhetorical ploys • Fallacies • Formal fallacies • Substantive fallacies • Further fallacies

Chapter 5: The practice of argument reconstruction 155

Extraneous material • Implicit and explicit • Connecting premises • Covering generalisations • Relevance • Ambiguity and vagueness • More on generalisations • Practical reasoning

• Balancing costs, benefits and probabilities • Explanations as conclusions • Causal generalisations • A shortcut

Chapter 6: Issues in argument assessment 206

Rational persuasiveness • Some strategies for logical assessment • Refutation by counter-example • Engaging with the argument: avoiding the 'Who is to say?' criticism • Argument commentary • Argument trees

Chapter 7: Truth, knowledge and belief 237

Truth and relativity • True for me, true for you • Truth, value and morality • Belief, justification and truth • Knowledge • Justification failure • Knowledge and rational persuasiveness • Gettier cases

Glossary 261

Index 273

Preface

Like all authors of texts on critical thinking or critical reasoning, we have tried to write a book that is genuinely useful. But our conception of what is useful differs somewhat from that of most of those authors.

On the one hand, we have avoided formal logical methods. Whereas the application of formal methods is justified primarily by its value in coping with complex logical structure, the logical structure of everyday argumentation is very seldom so complex that an argument's validity, or lack of it, cannot be revealed to ordinary intuition by a clear statement of the argument in English. Yet no formal means short of the first-order predicate calculus is sufficient to represent the logic of the majority of everyday arguments. Rather than compromise by presenting less comprehensive formal methods that are useful only in a narrow range of cases, we have avoided them entirely.

On the other hand, we have discussed and employed the concepts of logic more thoroughly than is customary in texts that avoid formal methods. We have defined them as accurately and in as much detail as we could, without superfluous refinement or inappropriate theoretical elaboration. We have done this for three reasons. First, it is only by grasping those concepts clearly that the student can achieve a stable and explicit understanding of the purposes of presenting and analysing arguments. Second, facility with those concepts enables the student to think and to talk about arguments in a systematically precise way; it provides a common currency in terms of which to generalise about arguments and to compare them. Third, experience, including our teaching experience, suggests that the concepts of logic themselves, when they explicitly appear in argumentative contexts, are amongst the most persistent sources of confusion. A symptom of this is the relativism that is so often encountered and so often lamented. At the root of this, we assume, are certain equivocations over the word 'truth'. We have tried to clear these up in a commonsense and non-dogmatic way, and thereby to clarify further concepts that depend on the concept of truth, such as validity, probability, inductive force, soundness, justification and knowledge. We hope that clarity about these concepts, and the ability to use them with confidence in analysing arguments, will be amongst the most valuable accomplishments to be acquired by studying this book.

We do not entirely accept the view that examples in a book on critical thinking should be real, or even that they should be realistic. Of course, the aim is that students should be able to deal with real arguments. But whereas real examples typically call for the exercise of several strategies and the application of various concepts at once, those strategies and concepts have to be learnt one at a time. Unrealistic, trumped-up examples are often much more useful for illustrating isolated concepts and points of strategy. We have tried to vary the realistic with the unrealistic as the situation recommends.

Chapter summaries are provided along with exercises, but we have not provided answers to the exercises. One reason is that in many cases there is no demonstrably correct answer. Another is that in many cases there is too much scope for different sorts of answer, different ways of putting a point or representing an argument. And more generally, we think it is just too tempting for students to consult the answers too soon. We anticipate that teachers will want to assign further coursework, especially where this involves the procurement and analysis of material from newspapers and the like.

Thanks to Lee Churchman and Damien Cole, both of whom updated earlier versions of this text for us in preparation for teaching, and thereby provided many helpful examples. Thanks also to all those who have provided ideas either as teaching assistants or students of our Critical Reasoning course at the University of Waikato: especially Paul Flood, Stephanie Gibbons, Andrew Jorgensen, Dawn Marsh, Alastair Todd, Louis Wilkins and Tim Wilson. We also thank the Philosophy Department at the University of Waikato for giving Bowell time to stay in Glasgow to work with Kemp in October 1999.

Every effort has been made to trace all copyright holders of extracts used in this book. If any have been inadvertently overlooked, the publishers will be pleased to make the necessary arrangements at the first opportunity.

Tracy Bowell, University of Waikato Gary Kemp, University of Glasgow January 2001

Introduction and preview

We are frequently confronted with people's attempts to get us to do and believe things, and often these attempts are arguments. This book aims to familiarise you with techniques of argument analysis and assessment so that you become able to assess the strength of any argument you may encounter and thus determine whether you ought to be persuaded by it.

Chapter 1 introduces the concept of argument as it should be understood for the purposes of critical thinking. Argument is distinguished from other linguistic means of getting people to do and to believe things. We introduce a method for laying out arguments so as to understand them more clearly, and we discuss various ways in which language can obscure an arguer's intended meaning.

Chapter 2 introduces two of the concepts required for the analysis and assessment of deductive arguments: validity and soundness. We discuss the assessment of validity and soundness, and explain the meaning and use of the Principle of Charity.

Chapter 3 continues our coverage of the concepts central to this book, this time for analysis and assessment of inductive arguments: inductive force and inductive soundness. We also discuss inductive inferences and degrees of probability.

Chapter 4 is a detailed discussion of rhetorical ploys and fallacies, two species of what we call 'sham-reasoning'. Common species of each are considered, and using the concepts and techniques covered in previous chapters, we provide a method for exposing and assessing fallacious reasoning.

Chapter 5 covers in more detail the techniques required for reconstructing arguments so that their strength can be accurately assessed. We demonstrate techniques for deciding which material is relevant to an argument; for dealing with ambiguous and vague language; for uncovering an argument's hidden premises; for adding connecting premises; for dealing with practical reasoning, and for dealing with causal arguments.

Chapter 6 is concerned with further concepts and techniques for argument assessment. We introduce the concept of rational persuasiveness, and introduce further techniques for assessing arguments and for refuting them. We also present argument trees as a graphical method of representing an argument's form.

Finally, in Chapter 7 we consider some of the philosophical issues underlying the concepts and techniques used here. We discuss truth and the relationship between truth, belief and knowledge, and relate these issues to the concept of rational persuasiveness.

Each chapter concludes with a chapter summary and some exercises. Where appropriate, the reader is encouraged to look outside the book for further examples to serve as exercises.

Chapter 1

♦ Beginning to think critically: recognising arguments

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