Critical Thinking
Third Edition
Richard L. Epstein
with Carolyn Kernberger
Illustrations by Alex Raffi
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Library of Congress Control Number: 2004110964
ISBN-13: 978-0-534-58348-4
ISBN-10: 0-534-58348-2
THE SLEEP OF REASON BEGETS MONSTERS
Dedicated to
Peter Adams
A great editor, a good friend.
With gratitude for his patience, encouragement,
and good advice that helped shape this book.
Critical Thinking
Third Edition
Cast of Characters
Preface to the Student
Preface to the Instructor
Acknowledgments
THE FUNDAMENTALS
1 Critical Thinking?
A. Are You Convinced? 1
B. Claims 2
C. Arguments 4
Summary 7
• Exercises for Chapter 1 7
Writing Lesson 1 12
2 What Are We Arguing About?
A. Vague Sentences
1. Too vague? 13
2. Ambiguous sentences 16
• Exercises for Section A 17
B. Subjective and Objective Claims 19
• Exercises for Section B 23
C. Prescriptive Claims and Value Judgments 24
• Exercises for Section C 25
D. Definitions 26
• Exercises for Section D 30
Summary 31
• Exercises for Chapter 2 32
Writing Lesson 2 35
3 What Is a Good Argument?
A. Good Reason to Believe 37
B. The Conclusion Follows From the Premises 38
C. The Tests for an Argument to Be Good 42
• Exercises for Sections A-C 46
D. Strong vs. Valid Arguments 48
Summary 48
• Exercises for Chapter 3 49
Writing Lesson 3 53
Cartoon Writing Lesson A 55
4 Repairing Arguments
A. We Need to Repair Arguments 59
B. The Principle of Rational Discussion 60
C. The Guide to Repairing Arguments 61
D. Relevance 68
• Exercises for Sections A-D 69
E. Inferring and Implying 74
• Exercises for Section E 75
Summary 76
Writing Lesson 4 78
Cartoon Writing Lesson B 80
5 Is That True?
A. Evaluating Premises 83
B. Criteria for Accepting or Rejecting Claims
1. Personal experience 84
• Exercises for Sections A and B.l 86
2. Other sources 87
Summary: When to accept and when to reject 90
• Exercises for Section B 91
C. Advertising and the Internet
Advertising 94
The Internet 94
• Exercises for Section C 95
D. Common Mistakes in Evaluating Premises
1. Arguing backwards 96
2. Confusing possibility with plausibility 97
3. Bad appeals to authority 97
4. Mistaking the person for the claim 97
5. Mistaking the person for the argument 98
• Exercises for Section D 99
Summary 101
Writing Lesson 5 103
Review Chapters 1-5 107
• Review Exercises 108
THE STRUCTURE OF ARGUMENTS
6 Compound Claims
A. Consider the Alternatives
1. Compound claims and "or" claims 113
2. The contradictory of a claim 114
• Exercises for Sections A. 1 and A.2 115
3. Reasoning with "or" claims 116
4. False dilemmas 118
• Exercises for Section A 119
B. Conditionals
1. Conditionals and their contradictories 120
• Exercises for Section B.l 122
2. Necessary and sufficient conditions 124
• Exercises for Section B.2 125
3. Valid and weak forms of arguments using conditionals 127
• Exercises for Section B.3 131
4. Reasoning in a chain and the slippery slope 132
5. Reasoning from hypotheses 133
Summary 134
• Exercises for Chapter 6 135
Writing Lesson 6 139
Cartoon Writing Lesson C 145
7 Counterarguments
A. Raising Objections 147
B. Refuting an Argument
1. Refuting directly 149
2. Refuting indirectly 149
3. Attempts to refute that are bad arguments 151
Summary 152
• Exercises for Chapter 7 153
Writing Lesson 7 155
8 General Claims
A. General Claims and Their Contradictories 159
• Exercises for Section A 162
B. Some Valid and Invalid Forms 163
• Exercises for Section B 167
C. Between One and All 170
• Exercises for Section C 172
Summary 173
Writing Lesson 8 174
Review Chapters 6-8 175
AVOIDING BAD ARGUMENTS
9 Concealed Claims
A. Where's the Argument? 181
B. Loaded Questions 182
C. What Did You Say?
1. Making it sound nasty or nice 182
2. Downplayers and up-players 183
3. Where's the proof? 184
4. Innuendos 185
D. Slanters and Good Arguments 185
Summary 186
• Exercises for Chapter 9 186
10 Too Much Emotion
Appeals to Emotion 191
• Exercises for Chapter 10 195
11 Fallacies A summary of bad arguments
A. What Is a Fallacy? 199
B. Structural Fallacies 199
C. Content Fallacies 201
D. Violating the Principle of Rational Discussion 202
E. Is This Really a Mistake? 202
F. So It's Bad, So What? 203
• Exercises for Chapter 11 204
Writing Lesson 9 206
Cartoon Writing Lesson D 207
ARGUMENTS for ANALYSIS
Short Arguments for Analysis 211
Complex Arguments for Analysis
The Structure of Arguments 221
• Exercises on the Structure of Arguments 225
Examples of Analysis 226
• Complex Arguments for Analysis 233
REASONING ABOUT OUR EXPERIENCE
12 Reasoning by Analogy
A. What is Reasoning by Analogy? 253
B. An Example 254
C. Judging Analogies 256
D. Analogies in the Law 257
Summary 259
• Exercises for Chapter 12 259
Writing Lesson 10 265
13 Numbers?
A. Misleading Claims with Numbers 268
B. Graphs 270
C. Averages 273
Summary 274
• Exercises for Chapter 13 275
14 Generalizing
A. Generalizing 279
• Exercises for Section A 281
B. What is a Good Sample?
1. How you can go wrong 283
2. Representative samples 284
• Exercises for Section B 286
C. When Is a Generalization Good?
1. Sample size 287
2. Is the sample studied well? 288
3. Three premises needed for a good generalization 288
4. The margin of error and confidence level 289
5. Variation in the population 290
6. Risk 290
7. Analogies and generalizations 291
Summary 291
•Exercises for Chapter 14 292
15 Cause and Effect
A. What is the Cause?
1. Causes and effects 302
2. The normal conditions 303
3. Particular causes, generalizations, and general causes 303
• Exercises for Sections A. 1-A.3 304
4. The cause precedes the effect 305
5. The cause makes a difference 305
6. Overlooking a common cause 305
7. Tracing the cause backwards 306
8. Criteria for cause and effect 307
9. Two mistakes in evaluating cause and effect 308
• Exercises for Section A 310
B. Examples 310
• Exercises for Sections A and B 315
C. How to Look for the Cause 317
• Exercises for Section C 318
D. Cause and Effect in Populations 320
1. Controlled experiment: cause-to-effect 320
2. Uncontrolled experiment: cause-to-effect 321
3. Uncontrolled experiment: effect-to-cause 321
• Exercises for Section D 323
Summary 329
Writing Lesson 11 331
Cartoon Writing Lesson E 337
Review Chapters 12-15 339
• Review Exercises 340
Evaluating Reasoning 341
Composing Good Arguments 345
Cartoon Writing Lesson F 347
Writing Lesson 12 349
Making Decisions 351
Using Examples in Reasoning
A. Examples for Definitions and Methods 355
B. Showing a General Claim is False 356
C. Showing an Argument is Not Valid 356
Summary 357
• Exercises on Examples 357
Truth-Tables
A. Symbols and Truth-Tables 359
B. The Truth-Value of a Compound Claim 362
• Exercises for Sections A and B 364
C. Representing Claims 365
• Exercises for Section C 367
D. Checking for Validity 368
• Exercises for Section D 370
Summary 372
Aristotelian Logic
A. The Tradition 373
B. Categorical Claims 374
• Exercises for Section B 375
C. Contradictories, Contraries, and Subcontraries 378
• Exercises for Section C 380
D. Syllogisms 381
• Exercises for Section D 383
Diagramming Arguments
A. Diagrams 385
• Exercises for Section A 388
B. Counterarguments 389
• Exercises for Section B 390
Glossary 391
Answers to Selected Exercises 400
Index 437
Preface to the Student
You can read this book on your own. There are plenty of examples. The exercises
illustrate the ideas you're supposed to master. With some effort you can get a lot
out of this text.
But if you read this book just by yourself, you'll miss the discussion and
exchanges in class that make the ideas come alive. Many of the exercises are
designed for discussion. That's where your understanding will crystallize, and
you'll find that you can begin to use the ideas and methods of critical thinking.
You'll get the most out of discussions if you've worked through the material
first. Read the chapter through once, with a pencil in hand. Get an overview. Mark
the passages that are unclear. You need to understand what is said—not all the deep
implications of the ideas, not all the subtleties, but the basic definitions. You should
have a dictionary on your desk.
Once the words make sense and you see the general picture, you need to go
back through the chapter paragraph by paragraph, either clarifying each part or
marking it so you can ask questions in class. Then you're ready to try the exercises.
You should try all the exercises. Many of them will be easy applications of the
material you've read. Others will require more thought. And some won't make
sense until you talk about them with your classmates and instructor. When you get
stuck, look in the back where there are answers to many of the exercises.
By the time you get to class, you should be on the verge of mastering the
material. Some discussion, some more examples, a few exercises explained, and
you've got it.
That pen
cil in your hand is crucial. Reading shouldn't be a passive activity.
You need to master this material. It's essential if you want to write well.
It's essential in making good decisions in your life. If you can think critically, you
can advance in your work. No matter where you start in your career, whether
flipping hamburgers or behind a desk, when you show your employer that you are
not only responsible but can think well, can foresee consequences of what you and
others do and say, you will go far. As much as the knowledge of this or that
discipline, the ability to reason and communicate will speed you on your way.
Those skills are what we hope to teach you here.
Preface to the Instructor
This textbook is designed to be the basis of classroom discussions. I've tried to write
it so that lectures won't be necessary, minimizing the jargon while retaining the
ideas. The material is more challenging than in other texts, while, I hope, more
accessible.
The chapters build on one another to the end. Rely on your students to read the
material—quiz them orally in class, call on them for answers to the exercises, clear
up their confusions. The exercises are meant to lead to discussion, encouraging the
students to compare ideas. Instead of spending lots of time grading the exercises,
you can use the Quickie Exams from the Instructor's Manual. It is possible to do the
whole book in one semester that way. I've chosen just the material that is essential
for a one-semester course, the essentials of reasoning well.
This course should be easy and fun to teach. If you enjoy it, your students
will, too.
Overview of the material
The Fundamentals (Chapters 1-5) is all one piece. It's the heart of the course. Here
and throughout there is a lot of emphasis on learning the definitions. It's best to go
through this in a direct line.
The Structure of Arguments (Chapters 6-8) is important. Chapter 6 on
compound claims—an informal version of propositional logic—is probably the
hardest for most students. There's a temptation to skip it and leave that material for
a formal logic course. But some skills in reasoning with conditionals are essential.
If you skip this chapter, you'll end up having to explain the valid and invalid forms
piecemeal when you deal with longer arguments. It's the same for Chapter 8 on
general claims—an informal introduction to quantifiers in reasoning—except that
the material seems easier.
Avoiding Bad Arguments (Chapters 9-11) is fun. Slanters and fallacies give
the students motive to look around and find examples from their own lives and from
what they read and hear. For that reason many instructors like to put this material
earlier. But if you do, you can only teach a hodge-podge of fallacies that won't