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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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Understanding Arguments: An Introduction to Informal Logic, Ninth Edition Walter Sinnot-Armstrong and Robert Fogelin
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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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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.