The statement “either the maid did it or the butler did” is a __________.

With Good Reason: A Guide to Critical Thinking

Christopher Foster Ashford University

James Hardy Ashford University

Gloria Zúñiga y Postigo Ashford University

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James Hardy, Christopher Foster, and Gloria Zúñiga y Postigo

With Good Reason: A Guide to Critical Thinking

Editor in Chief, AVP: Steve Wainwright

Executive Editor: Anna Lustig

Development Editor: Rebecca Paynter

Assistant Editor: Jessica Sarra

Editorial Assistant: Lukas Schulze

Production Editor: Catherine Morris

Media Production: Amanda Nixon, LSF Editorial

Copy Editor: Lauri Scherer, LSF Editorial

Photo Researcher: Amanda Nixon, LSF Editorial

Cover Design: Bambang Suparman Ibrahim

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Cover Image: juuce/iStock and espiegle/iStock

ISBN-10: 1621785661

ISBN-13: 978-1-62178-566-8

Copyright © 2015 Bridgepoint Education, Inc.

All rights reserved.

GRANT OF PERMISSION TO PRINT: The copyright owner of this material hereby grants the holder of this

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Brief Contents

Chapter 1: An Introduction to Critical Thinking and Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Chapter 2: The Argument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Chapter 3: Deductive Reasoning . . . . . . . . . . . . . . . . . . . . . . . . .59

Chapter 4: Propositional Logic . . . . . . . . . . . . . . . . . . . . . . . . 119

Chapter 5: Inductive Reasoning . . . . . . . . . . . . . . . . . . . . . . . 165

Chapter 6: Deduction and Induction: Putting It All Together . . . . . . . . . . . . . . . . . . . . . . 207

Chapter 7: Informal Fallacies . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Chapter 8: Persuasion and Rhetoric . . . . . . . . . . . . . . . . . . . 279

Chapter 9: Logic in Real Life . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363

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About the Authors xiii Acknowledgments xv Preface xvii

Chapter 1 An Introduction to Critical Thinking and Logic 1

1 .1 What Is Critical Thinking? 2 The Importance of Critical Thinking 3 Becoming a Critical Thinker 6

1 .2 Three Misconceptions About Logic 7 Logic Is for Robots 7 Logic Does Not Need to Be Learned 9 Logic Is Too Hard 10

1 .3 What Is Logic? 11 The Study of Arguments 11 A Tool for Arriving at Warranted Judgments 12 Formal Versus Informal Logic 14

1 .4 Arguments Outside of Logic 14 Arguments in Ordinary Language 14 Rhetorical Arguments 15 Revisiting Arguments in Logic 16

1 .5 The Importance of Language in Logic 17

1 .6 Logic and Philosophy 19 The Goal of Philosophy 20 Philosophy and Logical Reasoning 20

Summary and Resources 21

Contents

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Chapter 2 The Argument 25

2 .1 Arguments in Logic 26 Claims 29 The Standard Argument Form 31

2 .2 Putting Arguments in the Standard Form 33 Find the Conclusion First 34 Find the Premises Next 36 The Necessity of Paraphrasing 38 Thinking Analytically 39

2 .3 Representing Arguments Graphically 42 Representing Reasons That Support a Conclusion 42 Representing Counterarguments 45 Diagramming Efficiently 46

2 .4 Classifying Arguments 47 Deductive Arguments 48 Inductive Arguments 49 Arguments Versus Explanations 50

Summary and Resources 53

Chapter 3 Deductive Reasoning 59

3 .1 Basic Concepts in Deductive Reasoning 60 Validity 60 Soundness 62 Deduction 63

3 .2 Evaluating Deductive Arguments 66 Representing Logical Form 66 Using the Counterexample Method 68

3 .3 Types of Deductive Arguments 70 Mathematical Arguments 70 Arguments From Definitions 71 Categorical Arguments 72 Propositional Arguments 72

3 .4 Categorical Logic: Introducing Categorical Statements 73 Clarifying Particular Statements 76

Contents

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Contents

Clarifying Universal Statements 76 Accounting for Conversational Implication 78

3 .5 Categorical Logic: Venn Diagrams as Pictures of Meaning 80 Drawing Venn Diagrams 81 Drawing Immediate Inferences 84

3 .6 Categorical Logic: Categorical Syllogisms 91 Terms 91 Distribution 91 Rules for Validity 93 Venn Diagram Tests for Validity 94

3 .7 Categorical Logic: Types of Categorical Arguments 111 Sorites 111 Enthymemes 112 Validity in Complex Arguments 113

Summary and Resources 115

Chapter 4 Propositional Logic 119

4 .1 Basic Concepts in Propositional Logic 120 The Value of Formal Logic 121 Statement Forms 122

4 .2 Logical Operators 123 Conjunction 124 Disjunction 126 Negation 128 Conditional 129

4 .3 Symbolizing Complex Statements 133 Truth Tables With Complex Statements 135 Truth Tables With Three Letters 137

4 .4 Using Truth Tables to Test for Validity 140 Examples With Arguments With Two Letters 141 Examples With Arguments With Three Letters 144

4 .5 Some Famous Propositional Argument Forms 149 Common Valid Forms 149 Common Invalid Forms 152

Summary and Resources 158

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Contents

Chapter 5 Inductive Reasoning 165

5 .1 Basic Concepts in Inductive Reasoning 166 Inductive Strength 167 Inductive Cogency 170

5 .2 Statistical Arguments: Statistical Syllogisms 171 Form 172 Weak Statistical Syllogisms 173

5 .3 Statistical Arguments: Inductive Generalizations 174 Representativeness 175 Confidence Level 179 Applying This Knowledge 180

5 .4 Causal Relationships: The Meaning of Cause 181 Sufficient Conditions 181 Necessary Conditions 182 Necessary and Sufficient Conditions 183 Other Types of Causes 184 Correlational Relationships 184

5 .5 Causal Arguments: Mill’s Methods 186 Method of Agreement 187 Method of Difference 188 Joint Method of Agreement and Difference 189 Method of Concomitant Variation 190

5 .6 Arguments From Authority 192

5 .7 Arguments From Analogy 193 Evaluating Arguments From Analogy 194 Analogies in Moral Reasoning 197 Other Uses of Analogies 198

Summary and Resources 203

Chapter 6 Deduction and Induction: Putting It All Together 207

6 .1 Contrasting Deduction and Induction 208

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Contents

6 .2 Choosing Between Induction and Deduction 211 Availability 211 Robustness 212 Persuasiveness 214

6 .3 Combining Induction and Deduction 216

6 .4 Reasoning About Science: The Hypothetico–Deductive Method 218 Step 1: Formulate a Hypothesis 219 Step 2: Deduce a Consequence From the Hypothesis 219 Step 3: Test Whether the Consequence Occurs 220 Step 4: Reject the Hypothesis If the Consequence Does Not Occur 220

6 .5 Inference to the Best Explanation 225 Form 228 Virtue of Simplicity 229 How to Assess an Explanation 231 A Limitation 232

Summary and Resources 236

Chapter 7 Informal Fallacies 239

7 .1 Fallacies of Support 241 Begging the Question 241 Circular Reasoning 242 Hasty Generalizations and Biased Samples 243 Appeal to Ignorance and Shifting the Burden of Proof 245 Appeal to Inadequate Authority 246 False Dilemma 248 False Cause 249

7 .2 Fallacies of Relevance 251 Red Herring and Non Sequitur 251 Appeal to Emotion 252 Appeal to Popular Opinion 255 Appeal to Tradition 256 Ad Hominem and Poisoning the Well 257

7 .3 Fallacies of Clarity 261 The Slippery Slope 261 Equivocations 262 The Straw Man 264

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Contents

Fallacy of Accident 267 Fallacies of Composition and Division 268

Summary and Resources 273

Chapter 8 Persuasion and Rhetoric 279

8 .1 Obstacles to Critical Thinking: The Self 280 Stereotypes 280 Cognitive Biases 282

8 .2 Obstacles to Critical Thinking: Rhetorical Devices 289 Weasel Words 290 Euphemisms and Dysphemisms 291 Proof Surrogates 293 Hyperbole 294 Innuendo and Paralipsis 295

8 .3 The Media and Mediated Information 300 Manipulating Images 301 Advertising 302 Other Types of Mediated Information 306

8 .4 Evaluating the Source: Who to Believe 308 Reputation and Authorship 309 Accuracy and Currency 312 Interested Parties 312

Summary and Resources 314

Chapter 9 Logic in Real Life 319

9 .1 The Argumentative Essay 320 The Problem 321 The Thesis 322 The Premises 323

9 .2 Strengthening the Argumentative Essay 327 Clarification and Support 327 The Objection 329 The Rebuttal 330 Closing Your Essay 331

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Contents

9 .3 Practical Arguments: Building Arguments for Everyday Use 333 The Claim 333 The Data 334 The Warrant 334 Comparing the Models 335

9 .4 Confronting Disagreement 338 Applying the Principle of Accuracy 339 Applying the Principle of Charity 340 Balancing the Principles of Accuracy and Charity 341 Practicing Effective Criticism 342

9 .5 Case Study: Interpretation and Criticism in Practice 346 Examining the Initial Argument 347 Examining the Objection 347 Examining the Wording 348 Drawing a Conclusion 349

9 .6 Other Applications of Logic 349 Symbolic Logic 350 Computer Science 350 Artificial Intelligence 350 Engineering 351 Politics (Speech Writing) 351

Summary and Resources 351

Glossary 355

References 363

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James Hardy, Ashford University Dr. James Hardy is part of the core faculty of the Humanities & Science department at Ashford University. He obtained a PhD in philosophy from Indiana University, a master’s degree in philosophy from the University of Washington, and bachelor’s degrees in philosophy and psy- chology from Utah State University. He has taught philosophy at multiple universities since 1998 and has had the opportunity to teach across the general education spectrum, including courses in algebra, speech, English, and physics. Dr. Hardy’s favorite part of teaching is watch- ing students get excited about learning, helping them achieve their dreams, and seeing their excitement as new worlds of knowledge open up to them.

Dr. Hardy loves spending time outdoors hiking, backpacking, and canoeing—especially when he can do so with family members. He has lived all over the United States and has always found beauty and natural wonders wherever he has lived. The only time he is happier than when he is in nature is when he is spending time with his family.

Christopher Foster, Ashford University Dr. Christopher Foster is lead faculty of the Humanities & Science department at Ashford University. He holds a PhD in philosophy with a specialization in logic and language and a master’s degree in philosophy from the University of Kansas (KU). His undergraduate work was completed at the University of California–Davis, where he earned bachelor’s degrees in mathematics and philosophy. Dr. Foster began his career as a graduate teaching assistant at KU and went on to teach at Brigham Young University and Utah Valley University. Dr. Foster has a passion for philosophy and believes that digging deeply into life’s ultimate questions is often the best way to improve students’ critical thinking and writing skills. He lives in Orem, Utah, with his wife, Cherie, and two daughters, Avery and Adia.

Gloria Zúñiga y Postigo, Ashford University Dr. Gloria Zúñiga y Postigo is part of the core faculty of the Humanities & Science department at Ashford University. She earned a PhD in philosophy from the University at Buffalo, special- izing in ontology, ethics, and philosophy of economics. Her previous studies are in philosophy at the University of California–Berkeley and economics at California State University–East Bay. Dr. Zúñiga y Postigo’s present research interests include examinations of the effect in our experiences of moral, aesthetic, and economic phenomena; and value in the Brentano School, the Menger School, and the Göttingen Circle scholars. Teaching philosophy is one her greatest passions. She especially enjoys teaching informal logic, because it empowers students with a tool for distinguishing truth from the mere appearance of truth, thereby making it possible for them to achieve fulfilling lives with greater efficacy.