1705137148
思辨精英：英语辩论-构筑全球视角 [:1705132531]
1705137149
21.1 Criteria for Logical Assessment of Arguments
1705137150
1705137151
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:
1705137152
1705137153
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)
1705137154
1705137155
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.
1705137156
1705137157
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.
1705137158
1705137159
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:
1705137160
1705137161
Johnson and Blair Model of Argument Cogency
1705137162
1705137163
1705137164
1705137165
1705137166
Before examining each of the standards individually, a few words about how the standards relate to the structure of an argument is in order. The standard of acceptability applies to the evidence on which the argument is built. In other words, to be logically adequate, an argument needs to be based on evidence that is acceptable to the audience. The standards of relevance and sufficiency apply to the links that are drawn between evidence and claim. At minimum, the link needs to relate to the evidence-claim relationship. Sometimes, a link is relevant to a claim, but is still not sufficient. The relationship between those three criteria and the structure of argument that has been presented in this book is illustrated in the chart below:
1705137167
1705137168
Johnson and Blair’s Model applied to the Structure of Argument
1705137169
1705137170
1705137171
1705137172
1705137173
As the chart above indicates, the standard of acceptability applies to the element of argument called evidence, and the standards of relevance and sufficiency apply to the element of argument called the link. Each of those standards will now be considered individually.
1705137174
1705137175
思辨精英：英语辩论-构筑全球视角 [:1705132532]
1705137176
21.1.1 The Standard of Acceptability
1705137177
1705137178
As stated earlier, the standard of acceptability applies to evidence. As suggested in Chapter 16, evidence is the foundation of an argument. Without that element of argument, a claim cannot be established.
1705137179
1705137180
The standard of acceptability means that evidence must be acceptable to the judge or audience before the argument can proceed. Audiences and judges will have different levels of acceptability for any particular piece of evidence. For instance, an audience or judge may view certain evidence as “unquestionably true,” “probable,” “plausible,” etc. At minimum, the judge or audience ought to be willing to accept the evidence “for the purposes of this argument.” To say that evidence is acceptable “for the purposes of this argument” means that the audience or judge is willing to tentatively accept the evidence so that the argument can proceed.
1705137181
1705137182
Realizing that the standards for acceptability of evidence may vary from audience to audience and from circumstance to circumstance, this text suggests three conditions that determine, more or less, the acceptability of evidence. Govier (2009: 140-155) originally posited seven acceptability conditions that this text has reduced to three that are the most useful for debaters. Like other standards of argument quality, the position taken in this book is that evidence should be viewed as “more or less” acceptable rather than absolutely or categorically “acceptable” or “unacceptable.”
1705137183
1705137184
First, evidence can be considered acceptable if it is common knowledge. In other words, if the evidence is known to be accurate by virtually everyone in the debater’s audience, that evidence meets the condition of acceptability. Some examples that most would consider to be common knowledge include statements like “Nelson Mandela served as President of South Africa,” or “Mahandas Gandhi employed non-violent civil disobedience.”
1705137185
1705137186
Second, if evidence is not common knowledge, it could still be considered acceptable if a published source or a recognized authority supports it elsewhere. For instance, most people would not consider as common knowledge the idea that genetically modified food may do harm to our offspring. However, to make this evidence acceptable, a debater could cite a prestigious resource. The knowledge that this evidence was published by a reputable source would make it acceptable to most audiences. Recognized authorities also can be used to help a debater make evidence acceptable. For instance, quoting Liu Yang about challenges for females in the Chinese space program would make that information more acceptable because she was the first Chinese female astronaut.
1705137187
1705137188
Finally, evidence that is not common knowledge can be made acceptable by constructing a cogent sub-argument. In a case where a debater comes to believe that the evidence presented is of questionable acceptability to the judge or the audience, the debater can create a sub-argument to support the evidence. Using a cogent sub-argument to make evidence acceptable is illustrated as follows:
1705137189
1705137190
1705137191
1705137192
1705137193
The debater transforms the evidence of questionable acceptability into a claim supported by evidence that is acceptable. The original evidence of questionable acceptability can lead to an unsuccessful claim. To remedy that situation, the debater can transform or replace the old evidence by producing a new sub-claim, using new acceptable evidence, and that sub-claim can then replace the old evidence that was questionably acceptable, thereby producing a successful claim.
1705137194
1705137195
In summary, the standard of acceptability applies to evidence. Without acceptable evidence, the claim itself cannot be supported. Acceptable evidence meets one of three standards: It is common knowledge; It is supported by a respected publication or an authority, or it is supported by a cogent sub-claim. Those three standards are neither absolute nor perfect, thus, meeting one of them makes the evidence more-or-less acceptable, but not absolutely acceptable.
1705137196
1705137197
思辨精英：英语辩论-构筑全球视角 [:1705132533]