强攻指出逻辑错误题

joywzy

LSAT-2-II-5
5. A gas tax of one cent per gallon would raise one billion dollars per year at current consumption rates. Since a tax of fifty cents per gallon would therefore raise fifty billion dollars per year, it seems a perfect way to deal with the federal budget deficit. This tax would have the additional advantage that the resulting drop in the demand for gasoline would be ecologically sound and would keep our country from being too dependent on foreign oil producers.

Which one of the following most clearly identifies an error in the author’s reasoning?

(A) The author cites irrelevant data.

(B) The author relies on incorrect current consumption figures.

(C) The author makes incompatible assumptions.

(D) The author mistakes an effect for a cause.

(E) The author appeals to conscience rather than reason.

答案:C,不明白为什么会有incompatible assumption?

LSAT-6-III-22

22. The true scientific significance of a group of unusual fossils discovered by the paleontologist Charles Walcott is more likely to be reflected in a recent classification than it was in Walcott's own classification, Walcott was, after all, a prominent member of the scientific establishment. His classifications are thus unlikely to have done anything but confirm what established science had already taken to be true.

Which one of the following most accurately describes a questionable technique used in the argument?

(A) It draws conclusions about the merit of a position and about the content of that position from evidence about the position's source.

(B) It cites two prices of evidence, each of which is both questionable and unverifiable, and uses this evidence to support its conclusions.

(C) It bases a conclusion on two premises that contradict each other and minimizes this contradiction by the vagueness of the terms employed.

(D) It attempts to establish the validity of a claim, which is otherwise unsupported, by denying the truth of the opposite of that claim.

(E) It analyzes the past on the basis of social and political categories that properly apply only to the present and uses the results of this analysis to support its conclusion.

答案:A

11. Scientific research at a certain university was supported in part by an annual grant from a major foundation. When the university' s physics department embarked on weapons-related research, the foundation, which has a purely humanitarian mission, threatened to cancel its grant. The university then promised that none of the foundation' s money would be used for the weapons research, whereupon the foundation withdrew its threat, concluding that the weapons research would not benefit from the foundation' s grants.

Which one of the following describes a flaw in the reasoning underlying the foundation's conclusion?

(A) It overlooks the possibility that the availability of the foundation's money for humanitarian uses will allow the university to redirect other funds from humanitarian uses to weapons research.

(B) It overlooks the possibility that the physics department' s weapons research is not he only one of the university's  research activities with other than purely humanitarian purposes.

(C) It overlooks the possibility that the university made its promise specifically in order to induce the foundation to withdraw its threat.

(D) It confuses the intention of not using a sum of money for a particular purpose with the intention of not using that sum of money at all.

(E) It assumes that if the means to achieve an objective are humanitarian in character, then the objective is also humanitarian in character.

答案:A

4. Marianna: The problem of drunk driving has been somewhat ameliorated by public education and stricter laws. Additional measures are nevertheless needed. People still drive after drinking, and when they do, the probability is greatly increased that they will cause an accident involving death or serious injury

David: I think you exaggerate the dangers of driving while drunk. Actually, a driver who is in an automobile accident is slight1y less likely to be seriously injured if drunk than if sober.

In responding to Marianna 's argument. David makes which one of the following errors of reasoning?

(A) He contradicts himself.

(B) He assumes what he is seeking to establish.

(C) He contradicts Marianna 's conclusion without giving any evidence for his point of view.

(D) He argues against a point that is not one that Marianna was making.

(E) He directs his criticism against the person making the argument rather than directing it against the argument itself.

答案,我选了C

请教做指出逻辑错误题有什么好办法?有LSAT逻辑捷进大法中,说这种题最简单,如果练习多次后.可是,我错得非常多,而且不明原因.请大家多帮助,看看有什么好办法能解决?

谢谢先.

perfection

5） a tax of fifty cents per gallon would therefore raise fifty billion dollars per year=〉A gas tax of one cent per gallon would raise one billion dollars per year at current consumption rates。这中间有个假设是：消费量没有变化。
作者又接着说：This tax would have the additional advantage that the resulting drop in the demand ......,消费要下降。
这正是 C中的意思。
22） 可以找到答案，但说不清理由。大虾多指点。谢先。
11）
4）这种对话题，首先找反驳的焦点。
Marianna： Additional measures are nevertheless needed。因为现在人们仍旧酒后驾驶，并卷入严重 ......
David:你夸大了酒后驾驶的危险性，因为....应该是对其观点的说明。
Marianna 谈论的是否需要附加measures ，而David.....
C不对， 即使David给出了证据来证明David的观点，他的反驳仍然是错误的。

这种反驳题和逻辑错误题应该还是很复杂的。有些选项很难读懂。
书上建议：把每次出现遇到新的逻辑错误都记下来，以免下次出错。

lyricling

先说一句，我做这种题的时候基本上是用排除法。因为很多时候我不能一读完题就反应出原文的逻辑错误在哪里，往往是一边看选项，一边与原文对照，一边才有了思路。我在这里试着回忆一下自己做题的思路，还请高手批评指教。

LSAT-2-II-5
原文有两个结论:
1) it (gas tax )seems a perfect way to deal with the federal budget deficit.
第一个结论：提高燃油税将有助于解决财政危机（也即燃油税能够提高政府收入）。这个结论的假设是“提高燃油税不会导致燃油需求的下降”，否则该结论不能成立。
2) This tax would have the additional advantage that the resulting drop in the demand for gasoline would be ecologically sound and would keep our country from being too dependent on foreign oil producers.  
第二个结论: 提高燃油税还有另一个好处：那就是汽油需要的下降将带来对环境带来好处，并且减少本国对进口石油产品的依赖度。这个结论的假设是“提高燃油税将导致燃油需求的下降”。
可以看到，同一段文字推理中的两个结论是建立在两个完全相反的假设之上的，如果假设1成立，则结论2不成立；如果假设2成立，则结论1不成立。题目称之为incompatible assumption.

LSAT-6-III-22　
原文结论：
Walcott’s classifications thus  confirm what established science had already taken to be true.
原文证据：
Walcott was, after all, a prominent member of the scientific establishment.
文章的推理是这样的。因为W是一个prominent member,所以其classification 就可以confirm　what……
这种错误有点像诉诸权威。原文推出一个关于W’s classification(也就是A项中的抽象词position)的结论(confirm what….也就是A项中的merits and content of a position)，但并没有给出任何与这个结论本身内容有关的证据，而只是说因为这个position来自W，所以这个position就如何。反而，在本文的第一句话里还给出了W的classification不如其它recent classification的证据。
本文推理犯的错误就是，提出的证据不能支持结论。

11.
这道题实质上是一个weaken题
原文推理：
university承诺不会将Foundation的money用于武器研究　→　foundation认为该学校的武器研究不会从foundation获益。
其实学校不将foundation 的money用于武器研究，只能表明武器研究不能直接接受foundation的money，但如果学校拿到foundation的money，它就可以把用在其它地方的资金挪出来支持武器研究，所以尽管学校承诺不用foundation的money搞武器研究，但武器研究仍有可能间接地从foundation那里获益。
原文的推理链条有一个gap,那就是A项指出的这个possibility (the availability of the foundation’s money for humanitarian uses will allow the university to redirect other funds from humanitarian uses to weapons research. ),忽略了这种可能的存在，原文的推理就是untenable的。

Lsat8 II (4)
M的推论：
证据：目前仍有酒后开车者，而酒后开车将导致更多死伤性交通事故的可能　→　结论：应该实施更多的限制措施。
D的推论：（D的结论在其第一句话）
证据：酒后开车者less likely to be seriously injured than 清醒者　→　结论：M夸大了酒后驾车的危险性（也就是酒后驾车不怎么危险）

可以看到D推论的证据与M推论的证据说的不是一回事，M说的是酒后开车将导致更多的死伤性交通事故（有可能是肇事司机死伤，但更多的是行人或别的车辆的司机和乘客）；而D说的是肇事司机受重伤的可能性并不是很大。

而D的结论与M的结论说的也不是一回事，D的结论是酒后开车不怎么危险，而M的结论是应该实施更多的限制措施。
所以说D与M的推论其实是风马牛不相及的两件事。D看似在反驳M，其实D在讲一个与M的推论实质没有关系的推论。

另外，我很同意perfection的意见，因为毕竟没有受过关于逻辑推理的专门训练，一开始不知道如何辨别比较复杂的逻辑错误。而这种题又要求在充分理解原文推理关系的基础上，能够很好地将其逻辑方法用抽象的逻辑词汇表达出来。我觉得难就难在如何能从具体的推理中抽绎出抽象的逻辑表述。如果这些题变成常见的假设，weaken，支持等题去考，我想大多数人都能够找到与之相对应的具体化内容。所以，好的办法可能就熟悉题中出现过的所有逻辑错误，在抽象地逻辑层面上将其理解。再遇到这类题时心里就会有点底了。
至于这种题难是不难，得看各人的情况而定，也许有的人对逻辑技法很熟悉，所以就会觉得这类题比较简单。反正我错得最多的就是这种题了，第一遍做的时候觉得这种题很难，摸不着头，第二遍的时候就好多了。但还是没有解决得很好。

谬论，嘻嘻，请批评指教！

perfection

LSAT-6-III-22　
还不是非常明白。
A:它是从一种关于这个立场的资源的证据中而得出这个立场的优点和内容的.
按照这个答案的意思是：作者是用了一方的资料中证据来判断这方的观点的正确性。

但好像很难从中直接得出这点来?!

lyricling

source不一定是指的资料呀，比如这个消息来源于某某人，这也是一种source.

joywzy

lyricling,你分析得太好了,鼓掌!!!!

你说得对,确实有必要有将指出逻辑错误题归类,这样以后心里有点数.

我试着做了一下总结,请指正.

没有考虑另一种可能性SAT-2-IV-6,7-VI-11,10-IV-14
绝对数学和相对数字(比例)SAT-3-I-23,10-II-22
两件事等同:4-I-11,7-VI-22
没有提出证据: 8-II-4
词义:10-II-14,11-I-10
诉诸权威:6-III-22
所答非所说:8-II-4
incomptable assumption: 2-II-5

希望补充!!!!请lyricling多多帮助!谢谢.

lyricling

joyMM的认真精神值得我们学习！
接受MM建议，我也正在整理这方面的总结。
互相帮助，多交流呀。