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第二章：GMAT逻辑文章的两种论证Argument类型（选修）

2013-04-04 10:57阅读：

http://blog.sina.cn/dpool/blog/u/1567502341


第二章：两种Argument类型 (选修)
n 什么是Causal Argument?

从逻辑的角度上讲，论证分为：条件论证（Conditional Argument）,和原因论证（Causal Argument）。我们知道，几乎每一个Argument都会存在因果关系，但因果关系和原因论证是两回事。那到底什么是Causal Argument呢？它与Conditional Argument
到底有什么区别呢？我们通过下面的例子来对比一下这两种Argument:


Conditional Argument:
例子：因为GMAT获得了高分，所以这位学生被名校录取的机会很大。
本论证的特点：根据已知条件，强调本条件会有什么后果。
当我们来反对此论证的时候，我们会说：(1)这个学生其它成绩很差，例如TOEFL; (2)学校录取不仅仅看GMAT分数，还看别的方面。这些反驳都是在驳斥文章的结论，也就是想传达“就算GMAT获得高分，学生被名校录取的机会也不大”这样的信息。

Causal Argument:
因为GMAT获得了高分，所以说明这位学生努力学习了。
本论证的特点：根据已知条件，强调本条件发生的原因。
当我们来反对此论证的时候，我们会说：(1)可能由于题简单；(2)这位学生天生就很聪明。我们发现，这些反对并没有反驳结论“学生努力学习”，而是在找一个另外的原因来解释，为什么 “GMAT获得了高分”。

从以上对比，我们可以发现，这两种Argument在逻辑上是不太一样的，所以我们来对比一下：


 Conditional Argument
 Casual Argument
例子
 因为GMAT获得了高分。所以这位学生被名校录取的机会很大。
 因为GMAT获得了高分。所以说明这位学生努力学习了。
Premise
 GMAT获得了高分
 GMAT获得了高分
Conclusion
 这位学生被名校录取的机会很大。
 这位学生被名校录取的机会很大。

结论强调“一件事情会有什么结果”
 结论强调“一件事情的什么原因”
特点
 Conclusion不是Premise的原因
 Conclusion可以是Premise的原因。
本质
 文章强调“已知推出未知”
 文章强调“两个事件因果相联”

我们来看几个例子：

1. Guidebook writer: (1) I have visited hotels throughout the country and have noticed that in those built before 1930 the quality of the original carpentry work is generally superior to that in hotels built afterward. (2) Clearly carpenters working on hotels before 1930 typically worked with more skill, care, and effort than carpenters who have worked on hotels built subsequently.

Conclusion部分是第(2)句：“1930之前的carpenters比之后的更有skill和care.这句话就是第（1）句premise“1930之前的hotel质量超过之后建设的”的原因。也就是说Conclusion可以作为Premise的原因。它是原因论证Causal Argument.

2. (1)Two centuries ago, Tufe Peninsula became separated form the mainland, isolating on the newly formed Tufe Island a population of Turfil sunflowers. (2)This population’s descendants grow to be, on average, 40 centimeters shorter than Turfil sunflowers found on the mainland. (3)Tufe Island is significantly drier than Tufe Peninsula was. (4) So the current average height of Tufe’s Turfil sunflowers is undoubtedly at least partially attributable to changes in Tufe’s environmental conditions.

Conclusion部分是第（4）句，注意到里面有一个词”attributable”, 说明Conclusion是在探讨一件事情发生的原因，所以很有可能是原因论证Causal Argument. Concluision的意思是“高度是由于Tufe 的环境改变造成的。根据此结论可知Premise肯定在说关于高度的问题。所以Conclusion可以为Premise的原因。它是原因论证Causal Argument.

3. (1) Until now, only injectable vaccines against influenza have been available. Parents are reluctant to subject children to the pain of injections, but adults, who are at risk of serious complications from influenza, are commonly vaccinated. (2) A new influenza vaccine, administered painlessly in a nasal spray, is effective for children. (3) However, since children seldom develop serious complications from influenza, (4) no significant public health benefit would result from widespread vaccination of children using the nasal spray.

Conclusion是（4）句，意思是这个新的小孩用的疫苗没public health. Premise是（3），意思是因为小孩很少得并发症(Complications)。所以逻辑链条是：小孩很少得并发症，所以新的小孩用的疫苗没public heath. 我们发现Conclusion不是在探讨一件事情发生的原因，所以不是原因论证Causal Argument，而是条件论证Conditional Argument.

n 练习：判断以下文章是什么论证方式：Conditional Argument or Casual Argument?

1. Inspection system X and inspection system Y, though based on different principles, each detect all product flaws but they each also erroneously reject three percent of flawless products. Since false rejections are very costly, money will be saved by installing both systems, instead of either one or the other, and rejecting only products found flawed by both.

答案：这是Conditional Argument

2. In an attempt to reduce the crime rate, the governor is getting tough on criminals and making prison conditions harsher. Part of this effort has been to d

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