Understanding arguments an introduction to informal logic 9th edition pdf

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Understanding Arguments

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Understanding Arguments

An Introduction to Informal Logic

NINTH EDITION

Walter Sinnott-Armstrong Duke University

Robert J. Fogelin Dartmouth College

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v i i

CONTENTS

Preface XV

Part I How to Analyze Arguments 1

Chapter 1 Uses of Arguments 3

What Arguments Are 3

Justifications 4

Explanations 7

Combinations: An Example 10

Chapter 2 The Web of Language 17

Language and Convention 17

Linguistic Acts 19

Speech Acts 22 Performatives  23

Kinds of Speech Acts  26

Conversational Acts 28 Conversational Rules  31

Conversational Implication  33

Rhetorical Devices  36

Summary 38

Chapter 3 The Language of Argument 41

Argument Markers 41 If . . . , then . . .  43

Arguments in Standard Form 45

A Problem and Some Solutions 47 Assuring  48

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v i i i

Contents

Guarding  49

Discounting  51

Evaluative Language 54

Chapter 4 The Art of Close Analysis 59

An Extended Example 59 Clerk Hire Allowance, House of Representatives  59

Chapter 5 Deep Analysis 79

Getting Down to Basics 79

Clarifying Crucial Terms 83

Dissecting the Argument 83

Arranging Subarguments 85

Some Standards for Evaluating Arguments 90 Validity  91

Truth  93

Soundness  94

Suppressed Premises 96 Contingent Facts  97

Linguistic Principles  99

Evaluative Suppressed Premises  100

Uses and Abuses of Suppressed Premises  100

The Method of Reconstruction 102

An Example of Reconstruction: Capital Punishment 105

Part II How to Evaluate Arguments: Deductive Standards 111

Chapter 6 Propositional Logic 113

The Formal Analysis of Arguments 113

Basic Propositional Connectives 114 Conjunction  114

Disjunction  122

Negation  122

Process of Elimination  125

How Truth-Functional Connectives Work  126

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i x

Contents

Testing for Validity  128

Some Further Connectives  132

Conditionals 134 Truth Tables for Conditionals  136

Logical Language and Everyday Language  142

Other Conditionals in Ordinary Language  145

Chapter 7 Categorical Logic 151

Beyond Propositional Logic 151

Categorical Propositions 152 The Four Basic Categorical Forms  154

Translation into the Basic Categorical Forms  156

Contradictories  159

Existential Commitment  161

Validity for Categorical Arguments 162 Categorical Immediate Inferences  164

The Theory of the Syllogism  166

Part III How to Evaluate Arguments: Inductive Standards 177

Chapter 8 Arguments To and From Generalizations 179

Induction versus Deduction 179

Statistical Generalizations 183 Should We Accept the Premises?  184

Is the Sample Large Enough?  185

Is the Sample Biased?  186

Is the Sampling Procedure Biased?  187

Statistical Applications 189

Chapter 9 Inference to the Best Explanation and from Analogy 195

Inferences to the Best Explanation 195 Which Explanation Is Best?  198

Context Is Crucial  200

Arguments from Analogy 204 Are Analogies Explanations?  207

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Contents

Chapter 10 Causal Reasoning 215

Reasoning About Causes 215

Sufficient Conditions and Necessary Conditions 217 The Sufficient Condition Test  220

The Necessary Condition Test  221

The Joint Test  222

Rigorous Testing  225

Reaching Positive Conclusions  226

Applying These Methods to Find Causes 228 Normality  228

Background Assumptions  229

A Detailed Example  230

Concomitant Variation 234

Chapter 11 Chances 239

Some Fallacies of Probability 239 The Gambler’s Fallacy  239

Heuristics  241

The Language of Probability 243

A Priori Probability 244

Some Rules of Probability 246 Probabilities of Negations  246

Probabilities of Conjunctions  247

Probabilities of Disjunctions  248

Probabilities in a Series  249

Permutations and Combinations  250

Bayes’s Theorem 253

Chapter 12 Choices 263

Expected Monetary Value 263

Expected Overall Value 266

Decisions Under Ignorance 268

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Contents

Part IV Fallacies 273

Chapter 13 Fallacies of Vagueness 275

Uses of Unclarity 275

Vagueness 276

Heaps 278

Slippery Slopes 280 Conceptual Slippery-Slope Arguments  280

Fairness Slippery-Slope Arguments  282

Causal Slippery-Slope Arguments  285

Chapter 14 Fallacies of Ambiguity 291

Ambiguity 291

Equivocation 295

Definitions 299

Chapter 15 Fallacies of Relevance 307

Relevance 307

Ad Hominem Arguments 308 Inconsistency  311

Genetic Fallacies  311

Appeals to Authority 314

More Fallacies of Relevance 318 Appeals to Popular Opinion  318

Appeals to Emotion  319

Chapter 16 Fallacies of Vacuity 323

Circularity 323

Begging the Question 324

Self-Sealers 328

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Contents

Chapter 17 Refutation 333

What Is Refutation? 333

Counterexamples 334

Reductio Ad Absurdum 337

Straw Men and False Dichotomies 341

Refutation by Parallel Reasoning 343

Part V Areas of Argumentation 351

Chapter 18 Legal Reasoning 353

Components of Legal Reasoning 354 Questions of Fact  354

Questions of Law  355

The Law of Discrimination 361 The Equal Protection Clause  361

Applying the Equal Protection Clause  362

The Strict Scrutiny Test  363

The Bakke Case  364

Regents of the University of California v. Bakke  366

Legal Developments Since Bakke  368

Grutter v. Bollinger 369

Gratz v. Bollinger  375

Burden of Proof 381

Chapter 19 Moral Reasoning 383

Moral Disagreements 383

The Problem of Abortion 384 The “Pro-Life” Argument  385

“Pro-Choice” Responses   387

Analogical Reasoning in Ethics 392

Weighing Factors 394 “Abortion,” by Mary Anne Warren  397

“An Argument that Abortion Is Wrong,”     by Don Marquis  409

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Contents

Chapter 20 Scientific Reasoning 423

Standard Science 423

Scientific Revolutions 425 “Molecular Machines: Experimental Support for the Design

Inference,” by Michael J. Behe  427

“Living with Darwin,” by Philip Kitcher  440

Chapter 21 Religious Reasoning 449

“Five Reasons to Believe in God,” by William Lane Craig  450

“Seven Deadly Objections to Belief in the Christian God,”     by Edwin Curley  456

Chapter 22 Philosophical Reasoning 465

“Sanity and the Metaphysics of Responsibility,”     by Susan Wolf  469

“A Defence of Free Will Skepticism,”     by Derk Pereboom  483

Index 495

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xv

PREFACE

Traditionally, logic has been considered the most general science dealing  with arguments. The task of logic is to discover the fundamental principles  for distinguishing good arguments from bad ones.

For certain purposes, arguments are best studied as abstract patterns  of reasoning. Logic can then focus on these general forms rather than on  particular arguments, such as your attempt to prove to the bank that they,  not you, made a mistake. The study of those general principles that make  certain patterns of argument valid and other patterns of argument invalid is  called formal logic. Two chapters of this work are dedicated to formal logic.

A different but complementary way of viewing an argument is to treat it  as a particular use of language: Presenting arguments is one of the important  things we do with words. This approach stresses that arguing is a linguistic  activity. Instead of studying arguments as abstract patterns, it examines them  as they occur in concrete settings. It raises questions of the following kind:

What is the place of argument within language as a whole? What words or phrases are characteristic of arguments? How do these words function? What task or tasks are arguments supposed to perform?

When an approach to argument has this emphasis,  the study is called  informal logic. Though it contains a substantial treatment of formal logic,  Understanding Arguments, as its subtitle indicates, is primarily a textbook in  informal logic.

The ninth edition of Understanding Arguments differs from the eighth  edition in a number of ways. The most important change is simplification.  Many chapters have been shortened and streamlined. Our goal was to  remove tangents and complexities that confuse students so that the main  points could be understood more easily. In addition, the different kinds of  inductive arguments have been reordered to provide a better flow between  topics. Several sections have been split up and reorganized for clarity.  Some of the more difficult and confusing topics have been dropped. This  edition also contains new readings on moral and philosophical reasoning in  Chapters 19 and 22. These new readings make the text more accessible and  relevant to popular debates. Finally, we updated many examples, exercises,  and discussion questions throughout the text.

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xv i

Preface

Another major innovation that begins with this Ninth Edition is that readers of Understanding Arguments will also have free access to detailed lectures, exercises, and quizzes on all of the material in Chapters 1–17. There are over 100 mini-lectures keyed to almost 1000 corresponding questions. These supplementary materials are available for free on the Coursera website (https://www.coursera.org/) in a MOOC titled Think Again: How to Reason and Argue. We hope that these lectures and exercises help readers get the most out of this book.

This new edition has been influenced by our teaching of this material with various colleagues. In this regard, we would especially like to thank Ram Neta, who co-taught with Walter Sinnott-Armstrong on the Coursera website, as well as to many people at Coursera and in the Office of Instructional Technology at Duke University, who taught us to make these topics more accessible and lively. We received invaluable help from two student assistants—Joe Metz and Jason Bowers—in addition to the many others who helped us on previous editions. We are also indebted to the following reviewers: Dan Berger, Simpson University; William Brunson, University of Nevada–Las Vegas; Aaron Cobb, Auburn University– Montgomery; Nathaniel Goldberg, Washington and Lee University; Deke Gould, Augustana College; Robert Bruce Kelsey, Thomas College; Jung Kwon, Long Beach City College; Judith Little, SUNY–Potsdam; Diane Michelfelder, Macalester College; Rachel Mohr, University of Nebraska–Lincoln; Dennis Montgomery, Norfolk State University; Patrice Nango, Mesa Community College; Kurt Nutting, San Francisco State University; Michael Patton, University of Montevallo; Marc Pugliese, Saint Leo University; Eric Rovie, Georgia Perimeter College–Newton; and Catherine Womack, Bridgewater State University. At Cengage Learning and PreMediaGlobal, we received expert advice and assistance from Joann Kozyrev–Senior Sponsoring Editor, Debra Matteson–Product Manager, Prashanth Kamavarapu–Project Manager, Ian Lague–Development Editor, Kristina Mose-Libon–Art Director, and Joshua Duncan–Assistant Editor. Without all of these people, this book would contain many more mistakes than it undoubtedly still does.

Walter Sinnott-Armstrong Robert J. Fogelin

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1

I How to Analyze Arguments

Arguments are all around us. They bombard us constantly in advertisements; in courtrooms; in political, moral, and religious debates; in academic courses on mathematics, science, history, literature, and philosophy; and in our personal lives when we make decisions about our careers, finances, and families. These crucial aspects of our lives cannot be understood fully without understanding arguments. The goal of this book, then, is to help us understand arguments and, thereby, to understand our lives.

We will view arguments as tools. To understand a tool, we need to know the purposes for which it is used, the material out of which it is made, and the forms that it takes. For example, hammers are normally used to drive nails or to pound malleable substances. Hammers are usually made out of a metal head and a handle of wood, plastic, or metal. A typical hammer’s handle is long and thin, and its head is perpendicular to its handle. Similarly, in order to understand arguments, we need to investigate their purposes, materials, and forms.

Chapter 1 discusses the main purposes or uses of arguments. The material from which arguments are made is language, so Chapters 2 and 3 explore language in general and then the language of argument in particular. Chapters 4 and 5 use the lessons learned by then to analyze concrete examples of arguments in detail. The following chapters turn to the forms of arguments, including deductive forms in Part II (Chapters 6 and 7) and inductive forms in Part III (Chapters 8–12). Each form of argument comes with its own standards of adequacy. Part IV (Chapters 13–17) will then consider the main ways in which arguments can go astray, includ- ing fallacies of clarity, relevance, and vacuity. By the end of this journey, we should understand arguments much better.

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3

1

Uses of Arguments

What are arguments? In our view, arguments are tools, so the first step toward understanding arguments is to ask what they are used for—what people are trying to accomplish when they give arguments. This brief chapter will propose a definition of arguments and then explore two main purposes of arguments: justification and explanation. Both justifications and explanations try to provide reasons, but reasons of different kinds. Justifications are supposed to give reasons to believe their conclu- sions, whereas explanations are supposed to give reasons why their conclusions are true. Each of these purposes is more complicated and fascinating than is usually assumed.

WHAT ARGUMENTS ARE

The word “argument” may suggest quarrels or squabbles. That is what a child means when she reports that her parents are having an argument. Arguments of that sort often include abuse, name-calling, and yelling. That is not what this book is about. The goal here is not to teach you to yell louder, to be more abusive, or to beat your opponents into submission.

Our topic is the kind of argument defined by Monty Python in their justly famous “Argument Clinic.” In this skit, a client enters a clinic and pays for an argument. In the first room, however, all he gets is abuse, which is not ar- gument. When he finally finds the right room to get an argument, the person who is supposed to give him an argument simply denies whatever the client says, so the client complains that mere denial is different from argument, be- cause “an argument is a connected series of statements to establish a definite proposition.” This definition is almost correct. As we will see, the purpose of an argument need not always be to “establish” its conclusion, both because some conclusions were established in advance and because many reasons are inconclusive. Nonetheless, Monty Python’s definition needs to be modi- fied only a little in order to arrive at an adequate definition:

An argument is a connected series of sentences, statements, or propositions (called “premises”) that are intended to give a reason of some kind for a sentence, statement, or proposition (called the “conclusion”).

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4

CHAPTER 1 ■ Uses of Arguments

This definition does not pretend to be precise, but it does tell us what argu- ments are made of (sentences, statements, or propositions) and what their purpose is (to give reasons).

Another virtue of this definition is that it is flexible enough to cover the wide variety of arguments that people actually give. Different arguments are intended to give reasons of very different sorts. These reasons might be justificatory reasons to believe or to disbelieve some claim. They might, in- stead, be explanatory reasons why something happened. They might even be practical reasons to do some act. Because reasons come in so many kinds, arguments are useful in a great variety of situations in daily life. Trying to determine why your computer crashed, why your friend acted the way she did, and whether it will rain tomorrow as well as trying to decide which political candidate to vote for, which play to use at a crucial point in a foot- ball game, where to go to college, and whether to support or oppose capital punishment—all involve weighing and evaluating reasons.

It is inaccurate, therefore, to think of arguments as serving only one single, simple purpose. People often assume that you always use every argument to make other people believe what you believe and what they did not be- lieve before hearing or reading the argument. Actually, however, some ar- guments are used for that purpose, but others are not. To fully understand arguments in all their glory, then, we need to distinguish different uses of argument. In particular, we will focus on two exemplary purposes: justifica- tion and explanation.

JUSTIFICATIONS

One of the most prominent uses of arguments is to justify a disputed claim. For example, if I claim that September 11, 2001, was a Tuesday, and you deny this or simply express some doubt, then we might look for a calendar. But suppose we don’t have a calendar for 2001. Luckily, we do find a calen- dar for 2002. Now I can justify my claim to you by presenting this argument: The calendar shows that September 11 was on Wednesday in 2002; 2002 was not a leap year, since 2002 is not divisible by 4; nonleap years have 365 days, which is 1 more day than 52 weeks; so September 11 must have been on Tuesday in 2001. You should now be convinced.

What have I done? My utterance of this argument has the effect of chang- ing your mind by getting you to believe a conclusion that you did not believe before. Of course, I might also be able to change your mind by hyp- notizing you. But normally I do not want to use hypnosis. I also do not want to change your mind by manufacturing a fake calendar for 2002 with the wrong dates or by fooling you with a bad argument. Such tricks would not satisfy my goals fully. This shows that changing your mind is not all that I am trying to accomplish. I want more than simply to persuade you or convince

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5

Just if icat ions

you. What else do I want? My additional aim is to show you that you should change your mind, and why. I want my argument to be good and to give you a good reason to change your mind. I want my argument not only to persuade you but also to make you justified in believing my conclusion.

The above example is typical of one kind of justification, but there are other patterns. Suppose that I share your doubts about which day of the week it was on September 11, 2001. Then I might use the same argument to justify my belief as well as yours. Indeed, you don’t even need to be present. If I am all alone, and I just want to figure out which day of the week it was on September 11, 2001, then I might think in terms of this same argument. Here the goal is not to convince anybody else, but the argument is still used to find a good reason to believe the conclusion.

In cases like these, we can say that the argument is used for impersonal normative justification. The justification is normative because the goal is to find a reason that is a good reason. It is impersonal because what is sought is a reason that is or should be accepted as a good reason by everyone capa- ble of grasping this argument, regardless of who they are. The purpose is to show that there is a reason to believe the conclusion, regardless of who has a reason to believe it. Other arguments, in contrast, are aimed at specific peo- ple, and the goal is to show that those particular people are committed to the conclusion or have a reason to believe the conclusion. Such individualized uses of arguments seek what can be called personal justification.

There should be nothing surprising about different people having different reasons. I might climb a mountain to appreciate the view at the top, whereas you climb it to get exercise, and your friend climbs it to be able to talk to you while you climb it. Different people can have different reasons for the same action. Similarly, different people can have different reasons to believe the same conclusion. Suppose that someone is murdered in the ballroom with a revolver. I might have good reason to believe that Miss Peacock did not commit the murder, because I saw her in the library at the time the murder was committed. You might not trust me when I tell you that I saw her, but you still might have good reason to believe that she is innocent, because you believe that Colonel Mustard did it alone. Even if I doubt that Colonel Mustard did it, we still each have our own reasons to agree that Miss Peacock is innocent.

When different people with different beliefs are involved, we need to ask who is supposed to accept the reason that is given in an argument. A speaker might give an argument to show a listener that the speaker has a reason to believe something, even though the speaker knows that the audience does not and need not accept that reason. Suppose that you are an atheist, but I am an evangelical Christian, and you ask me why I believe that Jesus rose from the dead. I might respond that the Bible says that Jesus rose from the dead, and what the Bible says must be true, so Jesus rose from the dead. This argument tells you what my reasons are for believing what I believe, even if you do not accept those reasons. My argument can be used to show you that

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6

CHAPTER 1 ■ Uses of Arguments

I have reasons and what my reasons are, regardless of whether you believe that my reasons are good ones and also regardless of whether my reasons really are good ones.

The reverse can also happen. A speaker might give an argument to show a listener that the listener has a reason to believe something, even though the speaker does not accept that reason. Suppose that you often throw loud parties late into the night close to my bedroom. I want to convince you to stop or at least quiet down. Fortunately, you think that every citizen ought to obey the law. I disagree, for I am an anarchist bent on undermining all governments and laws. Still, I want to get a good night’s sleep before the protest tomorrow, so I might argue that it is illegal to make that much noise so late, and you ought to obey the law, so you ought to stop throwing such loud parties. This argument can show you that you are committed to its con- clusion, even if I believe that its premises are false.