从A—B这个简单命题来聊聊GMAT.docx

从 A ——> B 这个简单命题来聊聊GMAT
                PhD是什么东西，PhD的官方翻译Doctor of Philosophy, 哲学博士，其实不管什么专业，只要是博士，基本统称PhD，除了个别几个法学博士JD，教育学博士ED（请别想歪了，是Doctor of Education）外，PhD涵盖理学，工学，经济学，管理学，社会学等所有学科。有人曾跟我开玩笑说过， PhD是Permanent Head Damage, 永久性脑残者，这话不完全正确，PhD的一大特点就是钻牛角尖，但是这并不代表脑残。

       言归正传，在聊之前我们一定得先谈谈哲学，哲学里面有一个重要分支是逻辑学。我个人一直非常反感GMAT Critical Reasoning 的中文被翻译成了逻辑，其实GMAT C R考试和逻辑可以说几乎没有半点关系。如果各位带着逻辑学的思路来做GMAT CR题，那一定是走入了死胡同。GMAT CR 考察的其实是一种正常人的理性，不需要你是位严谨的逻辑学家。

        我们从 A ——> B 这个简单的逻辑元命题说起。 从逻辑学得角度，能support A ——> B 的 只有一个就是：它的逆否命题成立， 即 B上划线  ——> A上划线 。但是 GMAT 考试中， 能support    A ——> B 这个命题成立的可以有很多 哦，
        比如        1. 确认A的正确性
                        2. 确认B的正确性
                        3. A ——> C  这个是不成立的
                        4. C——>B  这个也是很难成立的
        反之，你要weaken  A ——> B 的话，以下几个也是可以的：
                        1. 确认A是不正确的
                        2. 确认B是不正确的
                        3. A ——> C  这个也是成立
                        4. C——>B  这个也是可能成立

        这个其实和逻辑是没有关系的，难道不是吗？ 因为CR根本就不是逻辑，你完全可以这样理解CR题： 某路人甲说了一句话：A——>B,  另外路人乙补充了一个新信息（选项ABCDE），如果你听了路人乙的新信息后对路人甲的话的相信度增加一点点就是加强结论，如果你听了路人乙的话对路人甲的话的相信度降低一点点，那就是削弱结论。你完全可以通过一个正常人的思维来做CR题。
        给大家举个历史上活生生的例子，让大家理解更深刻一点。

        看过清宫戏的同学肯定知道，清太祖努尔哈赤有个小老婆叫阿巴亥（多尔衮的妈妈），她很年轻也很漂亮；努尔哈赤的二儿子代善，年纪和阿巴亥相仿，代善是继承努尔哈赤皇位的最有力竞争者。老四皇太极为了打击代善，就编出了这样一个故事告诉努尔哈赤 ： 阿巴亥半夜12点给代善送夜宵，因此阿巴亥和代善是有私情的。

             命题是  A ——> B
             阿巴亥半夜12点给代善送夜宵  ——>  阿巴亥和代善有私情

        努尔哈赤听了不肯相信，就派他得助手去查，他得助手回来说： 没错，阿巴亥确实半夜12点给代善送夜宵，邻居们都看到。 努尔哈赤大怒，是不是确认A， support   argument.
        努尔哈赤再派一个助手去查，助手回来说:  没错，阿巴亥和代善确实有私情，我们看到过他们在一起谈恋爱，而且每次开会，只要有代善在场，阿巴亥就会穿的非常风骚。 努尔哈赤更怒，是不是确认了B， support。
        阿巴亥心想，不好，这下我不要被他们整死了吗，不行，我得说服努尔哈赤，阿巴亥说： 我半夜12点给代善送夜宵是为了巴结他，以后他当了皇上以后可以对我的儿子多尔衮好一点。 是不是  A —— > C （巴结代善而以）， 努尔哈赤听了，对啊，怒气消了一点，是不是weaken啊？

 我再举个GMAT的考题：
 A conservation group in the United States is trying to change the long-standing image of bats as frightening creatures. The group contends that bats are feared and persecuted solely because they are shy animals that are active only at night.Which of the following, if true, would cast the most serious doubt on the accuracy of the group’s contention?(A) Bats are steadily losing natural roosting places such as caves and hollow trees and are thus turning to more developed areas for roosting.(B) Bats are the chief consumers of nocturnal insects and thus can help make their hunting territory more pleasant for humans.(C) Bats are regarded as frightening creatures not only in the United States but also in Europe, Africa, and South America.(D) Raccoons and owls are shy and active only at night; yet they are not generally feared and persecuted.(E) People know more about the behavior of other greatly feared animal species, such as lions, alligators, and snakes, than they do about the behavior of bats.

这道题的结论是不是：  bats are shy that are active only at night  ——>  they feared and persecuted
                                                          A         ——>   B 

如果我告诉你                                  A          ——>   C     是不是立刻削弱结论了？  
         roccoons and owls are shy that are active only at night  ——> they are not feared and ersecuted
这样就削弱了。

再来一道题GMAT题：
Which of the following most logically completes the argument given below?
People in isolated rain-forest communities tend to live on a largely vegetarian diet, and they eat little salt. Few of them suffer from high blood pressure, and their blood pressure does not tend to increase with age, as is common in industrialized countries. Such people often do develop high blood pressure when they move to cities and adopt high-salt diets. Though suggestive, these facts do not establish salt as the culprit in high blood
pressure, however, because .

(A) genetic factors could account for the lack of increase of blood pressure with age among such people
(B) people eating high-salt diets and living from birth in cities in industrialized societies generally have a tendency to have high blood pressure
(C) it is possible to have a low-salt diet while living in a city in an industrialized country
(D) there are changes in other aspects of diet when such people move to the city
(E) salt is a necessity for human life, and death can occur when the body loses too much salt

怎么样削弱                   high salt diets   ——>   high blood pressure   呢？
                                                         A  ——> B
我告诉你，现在是       other aspects(more pollution, more work pressure,etc) ——>  high blood pressure
                                                       C  ——> B
是不是就削弱了。

    如何理解加强和削弱，你们都知道了吧？   想想阿巴亥，想想努尔哈赤。