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论证，是指能够用论据来证明论点的逻辑过程和方式。这个过程和方式通过推理形式进行，因此推理必须遵守一定的规则。推理的形式多种多样，但如果使用不当，就会出现各种逻辑错误。GRE写作中的Argument Task，正是通过各种论证错误的设置，考查考生的逻辑思维能力。为了帮助大家掌握Argument Task的出题思路，本文总结了七类常见的论证过程中的错误：时间轴论证错误、大数谬误、数字与比例不等价、实验与调查研究的有效性、集体和个体/普遍和特殊之间的推导、因果关系错误、错误类比。当然，还有其他的论证错误，因为不常见，在此不作讨论。
在进入论证错误讨论之前，首先需要明确一个问题：事实和结论不值得反驳。分清楚事实和结论是本书的一个非常重要的观点，因为在Argument Task中这两个部分本身的真实性是不值得反驳的，反驳的重点在于得出结论的过程。例如，题目文章给出一项民意调查，预测某人会当选总统。民调得出这一结果是事实，这个事实本身不值得质疑，但是该民调的有效性与其结果的准确性是可以质疑的。再例如，题目文章给出去年某人任市长、其在任期间有公司倒闭的信息，这些信息是事实，本身的真伪也不值得质疑，但是公司倒闭和某人当市长之间是否存在因果关系是可以质疑的。而结论不值得反驳，并非指结论的真实性不可质疑，而是指不应反驳结论本身，应质疑是否有充足的论据能让结论成立。例如，结论是选择某人当市长是明智的选择。单独来看，该结论是可能成立的，所以不能也不值得针对这个结论去反驳，但文章中给出的论据是否能够支持这一结论？这才是应该关注的问题。
另外，事实和结论不一定都是完整的句子，可能是半句甚至是句中的一部分。对于结论的判定，有以下三类情况：一是，A推出B，B推出C，C推出D，在该情况下，本书将D判定为最终结论；二是，如若C是方案，D是方案的结果，本书就把C判定为最终结论；三是，A推出B和C，B和C是平行关系，在该情况下，本书将B、C判定为最终结论。
具体结合例题如下：
最终推论为结论的情况（Day 64）
Collectors prize the ancient life-size clay statues of human figures made on Kali Island but have long wondered how Kalinese artists were able to depict bodies with such realistic precision.Since archaeologists have recently discovered molds of human heads and hands on Kali, we can now conclude that the ancient Kalinese artists used molds of actual bodies, not sculpting tools and techniques, to create these statues. This discovery explains why Kalinese miniature statues were abstract and entirely different in style: molds could be used only for life-size sculptures. It also explains why few ancient Kalinese sculpting tools have been found. In light of this discovery,collectors predict that the life-size sculptures will decrease in value while the miniatures increase in value.
本题中“Collectors prize the ancient life-size clay statues of human figures made on Kali Island but have long wondered how Kalinese artists were able to depict bodies with such realistic precision. Since archaeologists have recently discovered molds of human heads and hands on Kali”是事实；“collectors predict that the life-size sculptures will decrease in value while the miniatures increase in value”是结论。
方案为结论的情况（Day 68）
A recent study reported that pet owners have longer, healthier lives on average than do people who own no pets. Specifically, dog owners tend to have a lower incidence of heart disease.In light of these findings, Sherwood Hospital should form a partnership with Sherwood Animal Shelter to institute an adopt-a-dog program. The program would encourage dog ownership for patients recovering from heart disease, which should reduce these patients’ chance of experiencing continuing heart problems and also reduce their need for ongoing treatment. As a further benefit, the publicity about the program would encourage more people to adopt pets from the shelter. And that will reduce the incidence of heart disease in the general population.
本题中“A recent study reported that pet owners have longer, healthier lives on average than do people who own no pets. Specifically, dog owners tend to have a lower incidence of heart disease”是事实；“Sherwood Hospital should form a partnership with Sherwood Animal Shelter to institute an adopt-a-dog program”是结论。
平行推论为结论的情况（Day 30）
The following appeared as a recommendation by a committee planning a ten-year budget for the city of Calatrava.
“The birthrate in our city is declining: in fact, last year’s birthrate was only one-half that of five years ago. Thus the number of students enrolled in our public schools will soon decrease dramatically, and we can safely reduce the funds budgeted for education during the next decade.At the same time, we can reduce funding for athletic playing fields and other recreational facilities. As a result, we will have sufficient money to fund city facilities and programs used primarily by adults, since we can expect the adult population of the city to increase.”
本题中，“The birthrate in our city is declining: in fact, last year’s birthrate was only onehalf that of five years ago”是事实，“we can safely reduce the funds budgeted for education during the next decade”和“At the same time, we can reduce funding for athletic playing fields and other recreational facilities”是结论。