GMAT逻辑argument的角色十分重要，只有大家了解了逻辑题中的论点及其发挥的作用才能更好地解答题目。
一、GMAT逻辑argument在题型中的角色概括。
GMAT逻辑从argument解题也是一种重要的方法，在Bible中讲了一种总重要的方法就是用argument来区分不同的题型，大致上把题型分为了几个大类。我们经常提到的有the Structure-Based Family、the Assumption-Based Family和the Evidence-Based Family。我们习惯上称之为第几家族。在下面的讲解中我们会详细讲到。
二、GMAT逻辑argument在不同题型中的作用
1、第一个家族中的argument作用分析。
第一个家族中的must be、main point、point at issue、method of reasoning、flaw in reasoning、parallel reasoning和第四家族的cannot be true是需要看全部的argument。
1)其中，must be 和cannot be true两个类型做法有相同的地方，当然也有不同的地方。
相同的地方是看这类argument的时候，每个完整的句子都是一个statement，需要从每个句子完整的推出答案，不能只顾premise或者conclusion，而且推出的must be 或者cannot be true在原文中一定有依据。
比如：
The increasing complexity of scientific inquiry has led to a proliferation of multiauthored technical articles. Reports of clinical trials involving patients from several hospitals are usually coauthored by physicians from each participating hospital. Likewise, physics papers reporting results from experiments using subsystems developed at various laboratories generally have authors from each laboratory.
If all of the statements above are true, which one of the following must be true?
答案(B) Most reports of clinical trials involving patients from several hospitals have multiple authors.和它对应的是第二个句子Reports of clinical trials involving patients from several hospitals are usually coauthored by physicians from each participating hospital。LSAT的出题人连词都对的很工整，usually对照most coauthored对照multiple authors，只能说LSAT绕了2个弯把正确答案给改写了。
再如：
Sharks have a higher ratio of cartilage mass to body mass than any other organism. They also have a greater resistance to cancer than any other organism. Shark cartilage contains a substance that inhibits tumor growth by stopping the development of a new blood network. In the past 20 years, none of the responses among terminal cancer patients to various therapeutic measures has been more positive than the response among those who consumed shark cartilage.
If the claims made above are true, then each of the following could be true EXCEPT:
答案: (A) No organism resists cancer better than sharks do, but some resist cancer as well as sharks.也是可以找到原文的出处，They also have a greater resistance to cancer than any other organism.这个说明鲨鱼的cartilage比任何组织抗癌功能要有功效，所以不可能有别的组织和鲨鱼的功效是一样的，这里也是绕了2个弯。不同的是must be true是正确的选项，cannot be true是选不可能的情况。
2)main point和must be的区别。
这个bible中有个章节专门强调了，意思是main point一定是must be true的，但是概况的意思比must be true来的全面，比如，He is a good boy but he likes to eat a lot.这句意思表达了两层意思，当让你阐述main point的时候，需要把两层意思都表达出来，但是must be true可以是he is not a bad boy或者he likes to eat a lot。等问题是问你main point的时候，一定选那个概况全面的，有的答案可能是must be true的情况，但是概况了一部分，这个就不能选。
3)method of reasoning和point at issue的类似部分。
这个类似的部分argument一般是两个人对话，A表达第一个观点，B表达第二个观点：
method of reasoning问你B是用何种方式来回答A的，point at issue问你是他们相同的观点在哪里，不同的观点又在哪里。method of reasoning是需要分清整个argument的结构的，也是我前面说的argument结构的几种。
flaw in the reasoning，Bible列举了很多错误的方式，我觉得这个部分是需要背的，不仅是flaw in the reasoning中有用，对于其他的形式的argument中错误答案的样子也是有帮助的。
这些错误答案包括：
其中，比如第一种uncertain use of a term or a concept，出题中有些错误答案也是如此，比如一个题目原文中说，those people who regularly drink two or three alcoholic beverages a day and thereby exceed the caloric intake necessary to maintain their weight do not in general gain weight，错误的答案说Some people who regularly drink two or three alcoholic beverages a day avoid exceeding the caloric intake necessary to maintain their weight by decreasing caloric intake from other sources.看出来没有，错误的答案中添加了一个avoid和原文截然相反的意思。还有一道题目是说孩子和父亲用的是厨房中的rolling pins，而有个答案是说厨房用具kitchen utensils，显然厨房用具的范围比某个特定厨房产品大很多，这也是bible中说用scope去排除选项的一脉相随的精神。
还有，其中的一个错误是exceptional case/overgeneralization样本不能代表总体或者从个案中概括过度，比如有个例子说，3/4的律师工作很幸苦，那么结论是所以的律师工作都很幸苦，为什么错?因为样本不具有代表性，
最后，想提到的一个错误是false analogy就是类比错误，这个方法也是assumption证明的一个方法，记得一个例子是A说一个理论是经济学原理的，然后把这里理论运用到天文学上，然后问你这个题目的assumption是什么?Assumption是两个物体的类比关系，如果要削弱的话，也是两个类比关系中的不同，要加强也是这两个类比关系的共同性。
(详情请看 GMAT逻辑基础入门 Arguments)
2、第一个家族中的argument作用分析。
第二个家族是assumption/weaken/strengthen/justify/resolve the paradox。这类家族我觉得还是很有难度的。
1)个人感觉这类家族中读argument的重点是conclusion，如果你可以找到conclusion中的因果关系，很容易排除错误的选项，因为你找到了关键词。
比如：
Eva: A ”smart highway” system should be installed, one that would monitor areawide traffic patterns and communicate with computers in vehicles or with programmable high way signs to give drivers information about traffic congestion and alternate routes. Such a system, we can infer, would result in improved traffic flow in and around cities that would do more than improve drivers' tempers; it would decrease the considerable loss of money and productivity that now results from traffic congestion.
Luis: There are already traffic reports on the radio. Why would a “smart highway” system be any better?
Eva's argument depends on the assumption that
A. on “smart highways” there would not be the breakdowns of vehicles that currently cause traffic congestion.
B. traffic lights, if coordinated by the system, would assure a free flow of traffic
C. traffic flow in and around cities is not now so congested that significant improvement is impossible
D. the type of equipment used in “smart highway” systems would vary from one city to another.
E. older vehicle could not be fitted with equipment to receive signals sent by a “smart highway” system
我们可以看到这个argument的结论是such a system, we can infer, would result in improved traffic flow in and around cities that would do more than improve drivers' tempers; it would decrease the considerable loss of money and productivity that now result from traffic congestion.然后根据这个conclusion我们可以发现只有C符合这个结论所描述的情况，正确答案也是C。个人认为这个方法可以用在时间不够的情况下，这样的思路可以提供正确率和提高做题速度。weaken/strengthen也可以用这个方法。
2)resolve the paradox这类型的问题和assumption/weaken/strengthen有所不同。
第一是思路不同，assumption可以看conclusion，但是这类题目不行，因为有的题目就是没有conclusion，然你自己补充的，解决这类题目需要注意：
第一，surprising low/high rate of success，这类型的题目一般是说明事物有的复杂性。
第二，add the facts，比如有一道题目，是说工厂用了新方法去解决操作失误，
但是新方法培训后，工作的操作失误率还往上升，问你解释的原因，答案是因为只有工厂的人数达到很大规模才能开展这类培训，那由于基数多，所以失误率是上升的。
这类题目，个人感觉有点像新旧对比Newer + Older = Total amount,文中或出现2个元素，解释的答案中会出现第三个元素，还有的像 sales * amount= total profit的感觉。
(详情请看 GMAT逻辑题型中的argument分析 )
GMAT逻辑argument的结构在很大程度上能够帮助大家区分逻辑的题型，并为解题提供一种思路。大家一定要先了解逻辑argument结构的特点，并学会用它来解题。
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