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20.7 Exercise for Chapter 20
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· Take any of the motions used earlier in the text. Construct at least one consequential argument for the motion and another against the motion. Then construct at least one principled argument for the motion and another against the motion. In each case, follow the describe, associate, evaluate pattern.
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思辨精英：英语辩论-构筑全球视角 Chapter 21The Quality of Arguments: Fallacies in Argumentation
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Robert Trapp
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Chapter Outline
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21.1 Criteria for Logical Assessment of Arguments
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21.2 Three Basic Fallacies
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21.3 Summary
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21.4 Terms and Concepts from Chapter 21
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21.5 Discussion Questions for Chapter 21
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21.6 Exercise for Chapter 21
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Chapters 15 through 20 focused on the elements of argument, how those elements are structured to create arguments, and how various arguments can be combined into coherent patterns. Implicit in those discussions is the idea that some arguments are better than other arguments and that some arguments are of higher quality than other arguments. This chapter focuses directly on the quality of arguments and on the criteria that separate good arguments from poor ones.
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This chapter concentrates on the logical criteria that separate good arguments from poor arguments. Logical criteria for assessing the strength of an argument are important, but they are only part of the story. Other extra-logical elements, such as the elegance of an argument, how well an argument is adapted to the audience, and the clarity and passion with which the argument is expressed, are also important parts of the quality of an argument. This chapter covers only the logical criteria for assessing argument quality. The other elements are discussed elsewhere in this book, particularly in Chapter 14 that focuses on how an argument is delivered. The concept known as “fallacies” is used to address the logical quality of arguments. Fallacies point to errors in evidence or reasoning, errors that weaken or undermine the strength of an argument. Different textbooks treat fallacies differently; some list a large number of fallacies and treat each of them independently. For many people, approaches are cumbersome and less than coherent. Philosophers Ralph H. Johnson and J. Anthony Blair devised a system of identifying fallacies that depends on three simple criteria for a good argument, and they define a fallacy as being any violation of those criteria. This chapter follows the approach taken by Johnson and Blair of identifying the three criteria for a good argument, then detailing specific fallacies that are related to each of those three criteria.
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21.1 Criteria for Logical Assessment of Arguments
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Some who write about the logical assessment of arguments see argument quality as falling into the categories of either “adequate” or “inadequate.” For example, Professor Trudy Govier writes that:
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A cogent argument must pass all three [criteria for good argument.] All its premises must be acceptable. They must be relevant to the conclusion. And taken together they must provide adequate grounds for that conclusion. If any one of these conditions is not satisfied, the argument is not cogent. It does not offer strong support to the conclusion. (2009: 74-75)
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The viewpoint taken in this book is different. Rather than using a categorical logic of “good-bad” or “adequate-inadequate” to assess the quality of argument, this text uses a variable logic of “better-worse” or “more adequate-less adequate.” Rather than seeing arguments as falling into just two categories of “adequate” and “inadequate,” this text views arguments as ranging along a spectrum from especially poor to extremely good. Most arguments fall somewhere between those extremes. Few are so good that they cannot be improved by logical and extra-logical criticism. Similarly, few are so poor that they cannot be improved.
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Many times debaters express a desire to produce the perfect argument, the argument that has no possible refutation. That desire reflects a basic misunderstanding about the nature of debate. Debate exists to find critical points of disagreement about substantive and controversial issues. If disagreement does not exist, the issue is not debatable and, thus, is not the kind of issue that debaters engage. Therefore, the perfect argument, even if it were possible to produce, would be trivial because it would not be about a substantive and controversial issue. An argument about a substantive and controversial issue is, by its nature, never irrefutable. An argument about a substantive, controversial issue can never be proven beyond all doubt. Therefore, this text speaks of supporting a claim rather than proving a claim.
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The question is, what are some logical criteria for determining whether the support that an argument offers is more or less adequate or inadequate? The criteria used in this text follow directly the work of Johnson and Blair and, for the purposes of this text, will be called the Johnson and Blair Model of Argument Cogency. Following the Johnson and Blair model, this text maintains that the three criteria for assessing the quality of an argument are acceptability, relevance, and sufficiency (Johnson and Blair, 2006: 45-55). The following diagram, which this text has renamed the Johnson and Blair Model of Argument Cogency, is taken directly from their book (Johnson and Blair, 2006: 54) and illustrates those criteria:
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Johnson and Blair Model of Argument Cogency
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