GRE逻辑题到底有什么难点？

老师补充说到：“那要是我们不分类呢?那要是复习逻辑题也能同时复习作文呢?，逻辑题做对了阅读文章也更清晰了呢?保不齐还能提高口语水平呢?想要同时考GMAT的同学，逻辑题占了verbal的1/3，GMAT数学中的data sufficiency也是在用逻辑。所以你要不要试一试好好学一学?”

开门见山，我们看这道题。

In the past ten years, there have been several improvements in mountain-climbing equipment. These improvements have made the sport both safer and more enjoyable for experienced climbers. Despite these improvements, however, the rate of mountain climbing injuries has doubled in the past ten years.

Which of the following, if true, best reconciles the apparent discrepancy presented in the passage?

A. Many climbers, lulled into a false sense of security, use the new equipment to attempt climbing feats of which they are not capable.

B. Some mountain-climbing injuries are caused by unforeseeable weather conditions.

C. Mountain climbing, although a dangerous sport, does not normally result in injury to the experienced climber.

D. In the past ten years there have been improvements in mountain-climbing techniques as well as in mountain-climbing equipment.

E. Although the rate of mountain-climbing injuries has increased, the rate of mountain-climbing deaths has not changed.

一句话来概括就是：登山设备性能提高反而造成登山死亡率升高。

要选择一个选项去和解这个矛盾。而且这个选项必须是合理的并且完全可以通过已知信息推出来的。经常出现的混淆视听的选项可能有哪些?

比如，登山人数增多。但是由于题干中已经指出说是死亡率(百分比死亡人数)增高，所以绝对人数并不能解释此现象。所以，留给我们的有用信息只有—登山设备性能提高这一个条件而已。那么什么衍生行为能够被登山设备性能提高这一条件直接合理影响并且可以造成死亡率升高的结果呢?

人们开始变的更作了呗!所以此题应该选A。

看完了简单题，那我们看一个难一点的。

A photograph from 1843 is sometimes claimed to be the earliest surviving portrait of Abraham Lincoln (1809-1865), sixteenth President of the United States. The photograph shows a face without a cleft chin, whereas Lincoln’s chin was cleft. However, since skilled retouching of a photographic negative can undetectably change a feature such as a cleft chin in portraits produced from the negative, absence of a cleft chin is inconclusive as evidence that the photograph is not Lincoln.

Which of the following, if true, most seriously undermines the argument

A. Few of the authenticated photographs of Lincoln show his cleft chin, since during his presidency (1860-1865) he was bearded.

B. An authenticated photograph of Lincoln taken in 1846 clearly shows a cleft chin.

C. The photograph was made by the daguerreotype process, an early photographic process in which no negative was produced.

D. The 1843 photograph differs from authenticated photographs of Lincoln from the time before he was President in that those photographs show a man with a sunburned face and wearing rough clothes.

E. There is no surviving documentary evidence from Lincoln’s letters or elsewhere that he sat for a photograph at any time before 1846.

逻辑关系是：由于在负片上可以运用美图技术，所以即使照片的下巴和真人的不太一样，所以并不能说明照片不是林肯。

我们要做的是什么：削弱这个结论，所以我们目标要建立的结论应该是：能说明这个照片不是林肯。

跟上一道题一样，结论简历在一个假设上，这个假设为：负片上可以运用美图技术。

所以我只要证明这个假设不成立即可：比如1，没有负片;2，不会美图。

所以 此题应该选C。

那好，我们现在总结一下。任何逻辑都是会有假设premise和结论conclusion。找到一个逻辑的漏洞可以从两种方法入手，一种找到premise本身的缺陷，另一种则是找到推理的缺陷。举个栗子：

由于现在的车祸中越来越多的卷入了青少年，所以青少年开车问题很严重，所以在学校内部应该开设课程教青少年开车。

Premise的问题出在哪里?怎么影响结论?

车祸中卷入青少年，指代不清楚，有可能青少年是受害方;如以上假设成立，那么学校里开设教青少年开车的行为并不能减少此类车祸现象。可以削弱结论。

那逻辑的问题呢?

青少年和学校里的青少年可以画等号么?这里也是我们可以削弱的一个地方，即开车的青少年有可能是不上学的青少年。

如果此题出现在作文的argument题干，那我们也可以进一步通过在学校开办开车课程的可行性进行削弱。

所以总体来讲，我们任何逻辑都是由收集数据，分析数据，得出结论，推出下一结论的过程。我们的削弱和增强也可以在任何一个环节，也可以是削弱或者加强环节与环节之间的联系。