下载掌阅APP，畅读海量书库
立即打开
|
一、对假设条件的理解 |
能让结论成立，但是论证过程没有提到的事件可被认为是“假设条件”。假设条件在前提和结论之间架一座桥，让前提可过渡到结论，并且假设条件没有固定的内容。
GRE逻辑题中考查的assumption在英语词典中的定义是“a statement that is assumed to be true and from which a conclusion can be drawn”。从字面意思上说是与前提一起，帮助结论成立。
假设条件可以有以下属性：
（1）一定是文章中没有说过的事件。
用英语来理解是“assumption is something one takes for granted and is unstated”。注意unstated一词，如果考生发现某选项可以帮助推出结论，但这项的内容在原文中明确看到过，则这项一定不是假设题的答案。
（2）和结论是一个方向。
因为要支持结论成立，假设条件在逻辑上和结论必须是一个方向。
（3）可简单地认为考题中的假设条件都是必要条件。
其实假设条件可分为必要性假设条件和充分性假设条件，然而GRE逻辑考试中只考必要性假设题，因此我们也不需要了解这两种假设条件之间的区别。既然是必要条件，则如果没有这个条件，结论必须无法得出。
（4）答案倾向于和前提更相关的选项。
可以这么看假设条件：出题人认为前提推出结论有缺陷，逻辑不严谨，需要新增其他条件才能得出结论，所以假设条件可理解为前提和结论之间的过渡，解题过程中倾向于找一个和前提更相关的选项，因为要帮助前提架桥，以便于推出结论。
（5）假设条件是支持题的一种答案形式。
支持题要选出可增强前提推出结论可能性的选项，所以假设条件可能成为支持题答案的一种，但并不是所有支持题的答案都是假设条件。假设条件必须是原文中没有提过的事情，而支持题答案可以是文章中已经被描述过的事。假设题答案取非（negation）之后，会让原文结论得不出来，然而支持题不需要选项取非导致结论取非。
（6）假设题的整体解法和推理链题的其他题型类似。
（7）实在做不出时，猜选主语前或谓语后带有否定词的选项。
例1 For similar cars and drivers, automobile insurance for collision damage has always cost more in Greatport than in Fairmont. Police studies, however, show that cars owned by Greatport residents are, on average, slightly less likely to be involved in a collision than cars in Fairmont. Clearly, therefore, insurance companies are making a greater profit on collision-damage insurance in Greatport than in Fairmont.
Which of the following is an assumption on which the argument depends?
A. Repairing typical collision damage does not cost more in Greatport than in Fairmont.
B. There are no more motorists in Greatport than in Fairmont.
C. Greatport residents who have been in a collision are more likely to report it to their insurance company than Fairmont residents are.
D. Fairmont and Greatport are the cities with the highest collision-damage insurance rates.
E. The insurance companies were already aware of the difference in the likelihood of collisions before the publication of the police reports.
解析： 原文描述三件事情：在Greatport保险更贵；在Greatport碰撞少；保险公司在Greatport更赚钱。
假设要支持结论成立，因此我们要带着结论（保险公司在Greatport更赚钱）看选项，同时不能忘记前提，如果只是记结论，万一选项说到了前提相关的事件会来不及反应。
A项：“Greatport的车辆修理成本不会更贵”。车辆的修理成本和“赔偿金”一样，都是由保险公司支付的。支付得越多，则保险公司的利润越少，故此项可留下。
B项：“摩托车”是文章推理链之外的话题，不能选。
C项：“Greatport的居民更可能向保险公司报告事故”，报告越多，则公司利润越小，此项和结论的方向相反，不可选。
D项：“两个城市有一个共同点”，结论是一个比较级，两个城市的共性不能推出一个比较级，因此此项不正确。
E项：“保险公司意识到某件事”，如果只是意识到而没有采取行动，则客观世界不会受影响。排除E项。
正确答案为A。
例2 The milk of many mammals contains cannabinoids, substances that are known to stimulate certain receptors in the brain. To investigate the function of cannabinoids, researchers injected newborn mice with a chemical that is known to block cannabinoides from reaching their receptors in the brain. The injected mice showed far less interest in feeding than normal newborn mice do. Therefore, cannabinoids probably function to stimulate the appetite.
Which of the following is an assumption on which the argument depends?
A. Newborn mice do not normally ingest any substance other than their mothers' milk.
B. Cannabinoids are the only substances in mammals' milk that stimulate the appetite.
C. The mothers of newborn mice do not normally make any effort to encourage their babies to feed.
D. The milk of mammals would be less nutritious if it did not contain cannabinoids.
E. The chemical that blocks cannabinoids from stimulating their brain receptors does not independently inhibit the appetite.
解析： 题目问推理链的假设，所谓推理链就是要找“前提与结论”。
原文的结论为“cannabinoids probably function to stimulate the appetite”，可简单记为 “C和胃口”有关，导致结论成立的原因即为前提。因此原文的前提是“给老鼠注射一种化学物质，以阻止C影响大脑，导致老鼠没啥胃口”。
我们带着“C会影响胃口”来看选项，只要选项和这个事件有部分交集，或者和文章之前所述某个话题沾边，此项即可待选。
A项可读成“老鼠不消化除了乳汁之外的其他东西”。答案的方向是“C会影响胃口”，此项和所要的答案方向完全没有交集，属于“不沾边”的选项。
B项读成“C是唯一会刺激胃口的物质”。我们在做逻辑题和阅读题的时候，要有这样的思维：（1）要找一个出错概率小的选项。（2）答案是比较后的结果。因为我们要找“C和刺激胃口”之间的关系，此项和A比起来，肯定更好一些，因此B项优于A项。
C项读成“老鼠母亲不会鼓励小老鼠吃东西”，老鼠母亲和小老鼠之间的关系和答案方向“C与胃口”无关，肯定不对。
D项读成“乳汁有没有营养”。此项和答案方向完全无关。
读完前四个选项，得出B项更好一些。如果E项也无关，则答案即为B。但是同学们切记：（1）在没有看完五个选项之前，不要得出答案，因为答案是比较后的结果，不把五个选项都比较完，无法得出最好的选项。（2）排除一定不对的选项，不要对答案事先有明确的预判。只要选项和答案方向有交集，就可以推理了，所以先放着和答案的方向或原文提过的事件有交集的选项，然后再来对比哪个选项更好。
E项读成“阻止C的化学物质本身不会导致没有胃口”，此项和答案的方向肯定有交集。放着此项和B项进行对比。
在实际考试中时间压力特别大，很多情况下不允许考生进行深入的思考和推理，因此在逻辑题和阅读题中如果要对比几个选项，考生切记“尽量不选有最高级或比较级”的选项。（此招有风险，不是100%正确）所以此项答案选E。通过推理也可排除B选项。假设条件是必要条件，必要条件意味着没有这个条件结论不能成立。如果把B项取非，结论依然可以成立，则B项不是假设条件。不管cannabinoids是不是唯一导致没有胃口的物质，这个唯一性不是结论要追求的必要条件。是不是唯一导致没有胃口的物质结论一样可以成立，所以B项不可选。
例3 Most household appliances use electricity only when in use. Many microwave ovens, however, have built-in clocks and so use some electricity even when they are not in use. The clocks each consume about 45 kilowatt-hours per year. Therefore, households whose microwave oven has no built-in clock use 45 kilowatt-hours per year less, on average, than do comparable households whose microwave oven is otherwise similar but has a built-in clock.
Which of the following is an assumption on which the argument depends?
A. Households that do not have a microwave oven use less energy per year, on average, than do households that have a microwave oven.
B. Microwave ovens with a built-in clock do not generally cost more to buy than microwave ovens without a built-in clock.
C. All households that have a microwave oven also have either a gas oven or a conventional electric oven.
D. Households whose microwave oven does not have a built-in clock are no more likely to have a separate electric clock plugged in than households whose microwave oven has one.
E. There are more households that have a microwave oven with a built-in clock than there are households that have a microwave oven without a built-in clock.
解析： 题目问“argument”，依然找“前提和结论”
读完此文之后把话题串记为“有无内置钟和消耗45度电”之间的关系。（“话题”是理解和记忆全文和选项的最小单位。如何把读到的句子浓缩为“话题”？推荐两招：第一，把句子总结为“什么东西+怎么着”；第二，把句子总结为“XX与XX”之间的关系，XX优先为名词）。
总结完原文推理链之后，带着“钟和45度电”的关系来读选项，只要选项和话题部分沾边，就可以先放着进行对比。
A项有比较级，出现比较级就应思考比较对象和比较内容是否在文章中出现。此项是有无微波炉之间的对比，不是微波炉里面的钟和45度电的关系，因为比较内容没有出现，可以果断排除此项。
B项读成“内置钟和卖价”的关系，是无关话题，排除此项。
C项和“钟与45度电”这一话题完全没有联系，排除此项。
D项：一个选项中出现文章未提及的内容，如果借助常识推理几步后所得内容和预测的答案话题处于一个方向，也属于沾边选项。并不是不能推理，是不允许主观地自以为是地推理，但可以借用常识推理。如果有一个单独的钟，则也会使用电，所以此项提到了“内置钟与使用电”的关系，与话题有交集。
E项谈论户数相关的话题，和话题完全无关。
答案为D选项。
考生切记： 不可选项读到一半即对选项进行对与错的判断。正确的步骤是读完选项，然后把选项以话题方式总结出来，看总结出来的选项话题是否和原文提过的话题有联系，再进行判断。
例4 In response to mounting public concern, an airplane manufacturers implement a program with well-publicized goal of reducing by half the total yearly amount of hazardous waste generated by its passenger-jet division. When the program began in 1994, the division's hazardous waste was 90 pounds per production worker, last year it was 40 pounds per production worker. Clearly, therefore, charges that the manufacturer's program has not met its goal are false.
Which of the following is an assumption on which the argument depends?
A. The amount of nonhazardous waste generated each year by the passenger-jet division has not increased significantly since 1984.
B. At least as many passenger jets were produced by the division last year as had been produced in 1994.
C. Since 1994, other divisions in the company have achieved reductions in hazardous waste output that are at least equal to that achieved in the passenger-jet division.
D. The average number of weekly hours per production worker in the passenger-jet division was not significantly greater last year than it was in 1994.
E. The number of production workers assigned to the passenger-jet division was not significantly less in 1994 than it was last year.
解析： 在逻辑考题中，平均值和相对数是两个高频考点。此题考查平均值问题。如果题目中有平均值，则和计算平均值过程相关的事件就出题方向。（切记：不要对答案的方向有预判，这里只是展示了统计数据，如何选择还是应具体问题具体分析）
原文从“有害废物数值由人均90磅降至人均40磅”推出“计划成功了”。此结论是虚的内容，答案只会和“有害废物人均值”相关。出现平均值则意味着可能会考查其计算过程，所以在看选项之前想下“总有害废物数量除以总人数”得到人均有害废物值，如果不提前思考此计算过程，万一选项提到计算过程相关的事件，很多考生会反应不过来。
A项描述“非有害废物”和原文中“有害废物”没有关联，或可理解为没有话题的交集。排除此项。
B项中“生产一样多的飞机”不能联系到“人均有害废物减少”，但比A项好一些。
C项“其他部门”和原文中提到的部门没有交集，属于可以直接排除的选项。
D项的话题是“工作时长没有增加”。
E项的话题是“人数没有增加”。
根据原文中的“平均人数”的话题，肯定E项的“人数”与原文“平均人数”更沾边，故E项为答案。
技巧延伸： 如果原文说子集，选项说子集，两者不一定有关。就像C项和原文的关系一样。但如果原文说子集，选项说全集，子集和全集是肯定有交集，有类似逻辑关系的选项待比较。
例5 In January of last year the Moviemania chain of movie theaters started propping its popcorn in canola oil, instead of the less healthful coconut oil that it had been using until then. Now Moviemania is planning to switch back, saying that the change has hurt popcorn sales. That claim is false, however, since according to Moviemania's own sales figures, Moviemania sold 5 percent more popcorn last year than in the previous year.
Which of the following, if true, most strongly supports the argument against Moviemania's claim?
A. Total sales of all refreshments at Moviemania's movie theaters increased by less than 5 percent last year.
D. Total attendance at Moviemania's movie theaters was more than 20 percent higher last year than the year before.
E. The year before last, Moviemania experienced a 10 percent increase in popcorn sales over the previous year.
分析： A项中的食物和饮料（refreshments）与原文的爆米花是全集和子集的关系，此项为正确答案。
D项：原文并未说明人数增加与业绩额提升之间的转换率到达哪种程度才算是“好”，D项仅告知人数增加20%，我们无法判断原文中销售额增加5%是算好还是不好，故此项无关。
E项：前年的销量如何影响不了现在。除非文章告知不同时空会相互影响，比如“过去会影响到现在”，否则“过去”“现在”“将来”不同的时空相互独立。例如一个女生去年被同一个男生追求了十次没有成功，那么今年这个女生再被这个男生追求的话，结果是成功还是不成功？我们没法判断。因为结果可能是男生追求成功，也可能追求不成功。故E项不正确。
例6 In the United States, of the people who moved from one state to another when they retired, the percentage who retired to Florida has decreased by three percentage points over the past ten years. Since many local businesses in Florida cater to retirees, this decline is likely to have a noticeably negative economic effect on these businesses.
Which of the following, if true, most seriously weakens the argument?
A. Florida attracts more people who move from one state to another when they retire than does any other state.
B. The number of people who move out of Florida to accept employment in other states has increased over the past ten years.
C. There are far more local businesses in Florida that cater to tourists than there are local businesses that cater to retirees.
D. The total number of people who retired and moved to another state for their retirement has increased significantly over the past ten years.
E. The number of people who left Florida when they retired to live in another state was greater last year than it was ten years ago.
解析： 文章是通过“3%”这一数字进行逻辑推理，为“相对数”相关的考题。原文用“相对数”出题，答案往往用一个“绝对数”来削弱。（切记，不可仅记“相对数对应绝对数”的答案模式，还是要具体考题具体分析）
A项中有比较级，那么就应思考比较对象和比较内容是否在原文出现过，如果有一个没有出现，则属于无关对比，可以直接排除。
B项“离开佛罗里去其他州就业”和“退休后去佛罗里达的人数下降3%”无关。
C项：有部分学生觉得此项与原文有关，认为满足游客需求的生意好，则表示佛罗里达还是能赚到钱的。请问，这些学生犯了什么错误？他们把原文结论的内容修改了。原文结论并没有说佛罗里达是否能赚钱，而是“佛罗里达针对退休的人的生意不行了”。不可修改原文中的事件，这点在解阅读题时也尤其重要。把定位句的内容改了，答案就会选错。
D项说“退休后迁至其他州的总人数增加了”。该项没有针对佛罗里达来说，是一个全集性的说法，可涉及佛罗里达，属于沾边选项。并且，“相对数和绝对数”的出题套路让D项更加有理由留着待选。
E项与“佛罗里达针对退休人员的生意”无关，排除此项。
答案为D选项。有学生可能问，D选项为什么会成为正确答案呢？首先，如果五个选项中只有一个选项沾边，不需要再考虑这唯一的选项是如何推理出来的，只需要判断沾边即可。其次，逻辑题的支持或削弱不是一定要推出答案所涉事件，能增加或降低推理链所涉事件成立的概率即为支持或削弱。D选项通过逻辑可推理出：虽然相对数3%下降了，但是绝对总量多，即使退休人数少了3%，也会有充足的绝对数量来保障与退休人士相关的生意不受影响。但在实际考试中，各种压力会导致学生失去理性判断能力，所以纯逻辑推理的思路在考试中往往不适用。因此“沾边思维”对于解逻辑题和阅读题都有很大的好处。
通过补充的试题，学生可发现削弱题、支持题和假设题三者的做题思路类似，都是先判断选项是否和原文有话题交集，即是否沾边，然后再判断哪个选项与原文内容更相近。其实，不仅是这三种题型，评价题、解释矛盾题的解题方式也和沾边思维密切联系。逻辑推理能力薄弱的学生尤其要学习此类思维。
例7 Press Secretary: Our critics claim that the President's recent highway project cancellations demonstrate a vindictive desire to punish legislative districts controlled by opposition parties. They offer as evidence the fact that 90 percent of the projects canceled were in such districts. But all of the canceled projects had been identified as wasteful in a report written by respected nonpartisan auditors. So the President's choice was clearly motivated by sound budgetary policy, not partisan politics.
Which of the following is an assumption on which the press secretary's argument depends?
A. Canceling highway projects was not the only way for the President to punish legislative districts controlled by opposition parties.
B. The scheduled highway projects identified as wasteful in the report were not mostly projects in districts controlled by the President's party.
C. The number of projects canceled was a significant proportion of all the highway projects that were to be undertaken by the government in the near future.
D. The highway projects canceled in districts controlled by the President's party were not generally more expensive than the projects canceled in districts controlled by opposition parties.
E. Reports by nonpartisan auditors are not generally regarded by the opposition parties as a source of objective assessments of government projects.
解析： 第一步，找出原文的推理链。由“无党派审计人员说取消的项目是浪费的”推出“项目取消是因为预算，而不是党派偏见”。
第二步：看哪个选项和推理链或原文话题沾边。
A项：“唯一性”不是原文要研究的必要条件，类似的错误选项在之前的试题中出现过。排除此项。
B项：此项读成“浪费的项目和执政党”的话题，这个话题明显和文章内容有交集，先放着待选。
C项：“被取消的项目是执政党要承担的”。此项有党派倾向的意思，感觉是执政党故意要取消这些项目，和文章的结论相反，不选此项。
D项：“执政党控制的区域内取消的项目不会比反对党控制的区域内取消的项目更贵”。此项发现了比较级，要立刻思考比较对象和比较点是否都在原文中出现过。明显地，原文只提到过在“反对党控制的区域内项目取消”而不存在“执政党控制的区域内项目取消”的事件，所以此项属于无关对比，可排除此项。
E项：如果非党派人士的评估不被认为是客观的信息评价来源，那么此条件对于原文结论不是一个支持的方向，违反了假设条件要支持结论成立的原则，排除E选项。
只有B项和原文有关，无须推理，直接得出答案为B项。
例8 In Brindon County, virtually all of the fasteners—such as nuts, bolts, and screws—used by workshops and manufacturing firms have for several years been supplied by the Brindon Bolt Barn, a specialist wholesaler. In recent months many of Brindon County's workshops and manufacturing firms have closed down, and no new ones have opened. Therefore, the Brindon Bolt Barn will undoubtedly show a sharp decline in sales volume and revenue for this year as compared to last year.
The argument depends on assuming which of the following?
A. Last year the Brindon Bolt Barn's sales volume and revenue were significantly higher than they had been the previous year.
B. The workshops and manufacturing firms that have remained open have a smaller volume of work to do this year than they did last year.
C. Soon the Brindon Bolt Barn will no longer be the only significant supplier of fasteners to Brindon County's workshops.
D. The Brindon Bolt Barn's operating expenses have not increased this year.
E. The Brindon Bolt Barn is not a company that gets the great majority of its business from customers outside Brindon County.
解析： 原文的推理链可记成“Brindon的许多生产公司倒闭了”，推出“紧固件（fastener）供应商Barn收入比去年下降”，可简单记成“其他公司倒闭，Barn收入下降”。
A项：比较对象“前年”在文中没有提到，属于无关对比，可排除A项。
B项：此项的比较内容在原文中没有见过。假设条件是必要条件，如果取非必要条件，结论不能成立。即使幸存的公司业务量比去年大，因为生产公司的数量下降，依然可以导致Barn公司的收入下降，没有B项这个条件原文结论依然可以得出，所以排除此项。
C项：原文没有涉及唯一性，排除该选项。
D项：“运营成本没有增加”，此项和原推理链没有交集。单独看运营成本是否增加，无法得知Barn收入是否增加。
E项：“Barn不会从Brindon 之外获得生意”。学生不需要推理，肯定知道此项在描述“Barn和订单”的话题，则肯定与原文的结论“Barn收入”意思上有关联，所以E项为答案。从推理的角度也很容易理解，原文的前提是Brindon Country的生产公司数量减少，下游的公司倒闭，上游的供应商收入下降也符合生活中的经历。但如果Barn的大多数生意是来自Brindon这一城市之外呢？则即使城内收入下降，城外其他地方是Barn主要的收入来源，Barn的主要收入依然不受影响。故E为正确答案。