gmat备考复习逻辑讲义

1、GMAT 逻辑讲义吴强一、 归纳题：从上到下（从原文到） 读题 1） 注意条件句，如 if, as long as 等，例 第二册 P203 (20)2） 注意有没有否绝对化词，如 only，any，no, solely 等3） 注意有没有数学上的等式、不等式关系或比例(percent, proportion)等，例第二册第二册 P117 、 P126、 P169(1)、P248(14) 判断的原则：(1)中不能出现原文中没有的新概念（包括新的动词、形容词、名词等，但是需要同义词的出现）(2)若原文在某一信息点上没有绝对化概念，那么中也没有(3)不能出现新的比较(4)不能和原文信息相违背。例题

2、：第二册 P115 P116 P123 P126 推导结构例题 第二册P122 ， 讲义 section 1(19 题)2）理解命题及常用表达（这一知识点需要好好把握，不仅仅在归纳题中有用，在逻辑描述题中，逻辑结构一致性，对上文最好的批评等问法中都出现）原命题和逆否命题为等价命题，逆命题和否命题为等价命题(AB+C, 逆否命题为B/CA), (A+BC, 则其逆否命题为CAB)II. unless :=if not 即 not A unless B 表达为 ABA unless B 表达为非 ABonly if: A only if B 表达为ABif only: A if only B 表达

3、为BAA is necessary to B: BAWhenever, whoever, wherever :=if二、Weaken 和 Support 演绎题型（从下到上，即从到原文）weaken supportReasoningPremise（前提），（结论），Reasoning(推理过程，前提到结论的思维变迁)演绎题所的是一个“待评价的推理”，也就是从前提到结论的这个推理是否能够成立我是不知道的，我需要对它进行评价。根据问题的不同问法，确定不同的解题态度，问支持，就找一个选项说它可能对，问，找一个选项说它不一定对，问假设考虑使结论成立需要什么，哪一个是使其成立的一个必要条件。1如何正确理

4、解 weaken , support 支持：(support),将放在论据和结论之间，对原文推理或者结论有支持作用就可以，所以既可非充分又可非必要 驳斥：（weaken），将放在论据和结论之间，对原文推理或者结论有驳斥作用就可以，所以也是既可非充分又可非必要 如何理解充分和必要1充分：所谓充分条件就是仅有这条件就足以带来结果，不需考虑别的条件了。它是谁成立，谁一定也成立，比如 AB, 如果A 成立，那么一定有 B2必要：所谓必要条件就是没有这个条件结果一定不对。2前因后果结构推理中的前提和结论在大多数情况下用因果关系来表示，根据因果关系中的结果成立不成立我们分为两种逻辑结构，前因后果结果和 C

5、ausal Explanations 结构，以后讲的答案方向点区别并不大，但是我们为了利于理解进行这个分类前因后果结构表示： (AB)从这个原因是否能够得到这个结果？(注意 because, since, for 等原因引导词)这个方法是否能够达到这个目的？(注意 by 引导方法，To 的不定式引导目的)从这个条件是否能够得到这个结论？(注意 if，when, as long as 等引导条件)注意上面的结果、结论到底能不能够成立，目的到底能不能够达到，还不确定。驳斥、支持方向：A 方法可行， P122(7)A-B 之间 P113(3)、P116(12)A 之外因素的影响 B P113(2)、

6、P123(11)直接对 B 说 讲义 Section 1 第 4 题3Causal Explanationsa. 对一个事实的发生、一个现象的存在，一个研究的发现，提出一种解释也就是为什么这个事实会发生呢?为什么这个现象会存在呢?是这个原因导致的b. 从一个已知的,已经发生的事实,已经存在的现象中得到一个结论,这个结论其实还是对上面的事实发生、现象存在做出了一种解释 注意上面的结果、事实，现象都是已经发生，已经成立了，问到底是不是这个原因导致的，这也是 Causal Explanation 结构和前因后果结构最本质的区别，务必仔细体会。Causal Explanation 结构的典型引导词：r

7、esult、 due to、reason 、attribute to、hypothesize、the explanation is 、be responsible for、把这个事实当作 B, 把这个原因解释当作 A，方向： 这个原因和结果之间的关系？（B-A 之间）有没有别的原因来对上面的事实、现象、研究发现作出解释（A 之外的其他原因）支持：直接： 就是这原因导致结果，具体还可以表现为没有这个原因就没有这个结果。例题：讲义 Section 1 第 1 题， P201(12)间接：没有别的原因解释上面的事实或现象驳斥：直接：原因和结果无关，具体表现为有这个原因没有这个结果或者没有这个原因有这

8、个结果例题：P114(7), P115(9)间接：还有别的原因存在解释上面的事实或现象 P124(13)如何统一两种结构的方向？4Weaken, Support 读题：1）重点是找出原因和结果两句话，如果没有任何原因指示词，那么重点在结论，紧靠结论因果词（therefore ,thus）前面的往往就是原因2）对 to 的不定式要读出(往往表示为对一个目的提出一个方法)3）对 any, all, none, everyone, each, no, in general, on the whole等词需注意，因可能会为范围差异4）对 only, solely 加以注意，例：第四册：P18 5）对动

9、词的程度修饰，例：第四册：P7 5. 一些辅助的类型范围差异、数据得结果、因果顺序、比较原则三：“Assumption”题型假设定义：使结论成立的必要条件 读题： 和 weaken ,support 读题方法完全一样，再注意 when、if 等词语方向：前因后果结构1)因果关系差异概念的桥梁作用 (A-B 之间)例题：P115(8)、P122(5)、P200(7)、P202(15)、P248(12)、P249(16)2)A 可行性或者原因有意义：P228(9)、P246(7)3)没有其他的因素来影响这个结果或者结论 P248(12)、P250(18)Causal Explanations:1)

10、没有这个原因就没有这个结果 （两者之间）3)没有其他的原因来解释上面的事实或者现象 P173(16)、P229(13)注意此类假设其中，很可能会有词或类似概念出现注意： 和 weaken、support 一样，这两种结构的方向完全可以统一四：“evaluate”题型1定义： 对某个问题两方面的回答（yes and no）或者某个信息两方面的回答，对原文推理如果一方面回答起到支持作用，则另一方面回答起到驳斥作用，如果一方面回答起到驳斥作用，则另一方面回答起到支持作用，这个问题或者信息就对原文有评价作用。注意一定是 yes and no 回答都起到作用，如果仅仅一方面回答起到作用，则不是评价2.方

11、向： 1）直接说，结果和原因之间有没有关系(A-B) 例：第二册P172(10)、P198(3)2）A 是否可行或者有意义。 讲义 section 1(11 题)3）间接性：除 A 之外是否还有别的因素影响 B， 例：第四册 P104 或者有没有其他的原因来解释原文中存在的事实或者现象注意：evaluation、 assumption 和 weaken, support 的统一五：解释现象1解释 result, situation 等，统称为解释结果具体读出要解释什么，现象是什么，解题要点：抓住要解释的对象，具体变化2解释，找一个选项说明为什么会存在这种，解题主要抓住区别点3要明确，满足无推导

12、、无充分性。讲义 section 1(第 20 题)六完成一段话“题型”找需满足：1）在句子意思上满足原文，特别是可将最后一句话补全2）必须和原文前半段描述有关系例：第二册：P60 P70 P201 七“上文使用何种有疑问技术”题型（逻辑描述）并不是让你找一个选项对上文推理进行驳斥，也不是问原文推理的缺陷，而是让你用逻辑描述的语言来描述一下原文的推导过程。例：第三册 P4 （17）第四册 P85 八、提高（由学生自己去训练培养对 weaken support 等题的感觉）1Weaken:求异 2Support:求同所谓求同、求异就是和原文的一致或不一致，而不是中谁与谁一致或不一致，它要求既不要

13、考虑原文的因果之间为什么会如此，也不要考虑中因果之间为什么会如此，更不可考虑此是如何使得对原文有支持或驳斥作用的，而仅仅辨认在满足和原文有关时是保持和原文一致还是不一致，这一点往往对于难题来讲，特别还仅仅剩下两个选项需要辨别的时候，更为有用例：“因为这儿有个人，所以蚂蚁有两条腿。”对这一论证的支持或驳斥不应考虑为什么人和蚂蚁有关，而只考虑在中说有人或说蚂蚁两条腿的情况下，找其相同或不同就可以了，如“相邻近处没有人，蚂蚁也有两条腿”，在满足说蚂蚁有两条腿时说的是没有人，和上边论述不一致，因此可 weaken 同理说“在邻近处没有人，蚂蚁也就无两条腿，”就有 support 作用，你所需做的仅仅是

14、寻找相同或不同点，仅此而已，大家可由第三册上 P1 P2 P3 P5 P28 P29 P46 P47 等题去理解 weaken，由第二册上 P30 P31 P45 P48 等理解 support.九、最后读题GMAT 改为机考后，逻辑题长度明显增加，对此除提高阅读能力外（不是阅读技巧），主要要做训练看对一段话中在仅读一遍的情况下，究竟哪句话为结论，然后看出和结论相关的直接原因是什么，最后次要地看出和直接原因相关的性质点中，原文提出过什么就可以了，但对于“归纳”题型只能学会一边读一边思考原文的层次是什么，脑中将层次留下，无其他好方法。Section 11. The town of Stavang

15、er, Norway, was quiet andpeaceful until the early 1960s, when Stavangerbecame Norways center for offshore oil exploration.Between then and now, violent crime and vandalismin Stavanger have greatly increased. Clearly, thesesocial problems are among the results of Stavangersoil boom.Which of the follo

16、wing, if it occurred between theearly 1960s and now, gives the strongest supportto the argument above?(A) The people of Stavanger rarely regret that theirtown was chosen to be Norways center foroffshore oil exploration(B) Norwegian sociologists expressed grave concernabout the increase in violent cr

17、ime andvandalism in Stavanger.(C) Violent crime and vandalism have remained lowin Norwegian towns that had no oil boom.(D) Nonviolent crime, drug addiction, and divorcein Stavanger increased approximately asmuch as violent crime and vandalism did.(E) The oil boom necessitated the building of widerro

18、ads for the increased traffic in Stavanger.2. Since 1945 there have been numerous internationalconfrontations as tense as those that precipitated theSecond World War, and yet no large-scalehas resulted. To explain this, some argue that fearof enormous destruction such as the Second WorldWar produced

19、 has had a dramatic deterrent effect.Which of the following, if true, most seriouslyweakens the deterrent theory mentioned above?(A) After the First World War, the fear of greatfuture destruction was as intense as it wasafter the Second World war.(B) Psychologists have determined that the fearof ret

20、aliation tends to temper aggressivenessamong human beings.(C) The Second World War was far less destructivethan most people generally believe.(D) Fear of repeating the levels of destruction thatthe Second World War produced is as pervasivetoday as it was forty years ago.(E) Many of the international

21、 confrontations thathave occurred since 1945 have involved countriesthat participated in the Second World War.3. A list of the fifteen operas most frequently performedin recent times includes no works by the nineteenthcentury German composer Richard Wagner. Althoughmusic producers tend to produce wh

22、at audiences want,relative infrequency of performance probably doesnot indicate lack of popularity in Wagners case, sinceWagners operas are notoriously expensive to performon stage.Which of the following, if true, most stronglysupport theof the argument above？(A)The list of most frequently performed

23、 operasdoes not include operas produced by smallamateur groups.(B)Some opera companies are backed by patronswho are willing to commit large sums ofmoney in order to enjoy lavish productions.(C)All of the fifteen most frequently performedoperas of recent times are works that havebeen popular for at l

24、east 75 years.(D)More recordings have been produced recently ofthe works of Wagner than of the works of anyother composer of opera.(E)Operatic works of all kinds have been increasingin popularity in recent years.4. V-shaped walled structures in central Asiawere used by prehistoric hunters who droveh

25、oofed animals into an enclosure at the pointof the V. The central Asians who built thesestructures probably learned this huntingtechnique from invaders from southwest Asia,because the arrival of invaders from a regionin southwest Asia where similar structures hadlong been used coincides roughly with

26、 thebuilding of the earliest of such structures incentral Asia.Which of the following, if true, most strengthensthe argument?(A) Excavations in the central Asian region donot indicate whether invaders fromsouthwest Asia settled permanently incentral Asia.(B) The V-shaped structures in central Asiawe

27、re roughly 70 meters long, whereas thesimilar structures in southwest Asia wereusually over 300 meters long.(C) The walls of the structures in central Asiawere made from earth, whereas the wallsof the structures in southwest Asiawere made of rock.(D) The earliest examples of V-shaped walledstructure

28、s in central Asia were of anadvanced design.(E) Some of the walled structures used forhunting in southwest Asia were built wellafter the earliest such structures were builtin central Asia.5. The average age and racing experience of the driversat the Indianapolis 500 automobile race increasedeach yea

29、r between 1965 and 1980. The reason forthe increase is that high-speed racing drivers wereliving longer than their predecessors. Race-car safetyfeatures that reduced the severity of crashes of thekind that formerly took drivers lives were primarilyresponsible for the increase in the average age of t

30、heIndianapolis 500 competitors.Which of the following, if true, would be most likelyto be part of the evidence used to show that safetyfeatures on the cars that protected drivers in majorcrashes were responsible for the increase in theaverage age of drivers at the Indianapolis race?(A) Younger drive

31、rs at high-speed racetrackswere involved in major accidents at aslightly higher rate than were older driversbetween 1965 and 1980.(B) Major accidents on high-speed racetracksoccurred at about the same frequency in theyears after 1965 as in the years before 1965.(C) The average age of drivers attempt

32、ing toqualify for the Indianapolis 500 decreasedslightly between 1965 and 1980.(D) Accidents on highways in the United Statesoccurred at about the same frequency in theyears after 1965 as in the years before 1965.(E) Other safety features, involving the condition ofthe racetrack and the uniforms wor

33、n by thedrivers while driving, were adopted atIndianapolis between 1965 and 1980.6. Calvin: Fire insurance policies are disadvanta-geous to policyholders. The typical poli-cyholder always pays more in premiumsthan he or she collects in payments onpolicies.Lorraine: Yes, but policyholders are still r

34、ight inthinking that it is to their advantage tohold an insurance policy. The peace ofmind that comes from having an insurancepolicy is the main advantage to the poli-cyholder.Lorraine addresses Calvins argument by(A) Questioning the source of Calvins factual infor-mation(B) introducing a considerat

35、ion neglected byCalvins argument(C) showing that Calvins argument assumes whatit sets out to prove(D) challenging the truth of the evidence advancedin Calvins argument(E) showing the irrelevance of Calvins evidence tothehe draws7.X: When a rare but serious industrial accidentoccurs, people respond b

36、y believing that suchaccidents areing more frequent. Thisbelief is irrational. After all, being dealt fouraces in a hand of poker, a rare event, hardlyincreases ones chances of being dealt four acesin a future hand.Y: To the contrary, the belief is rational because itresults in peoples sensing a dan

37、ger to them-selves not previously sensed and taking precau-tionary actions to prevent similar accidents inthe future.Ys attempt to counter Xs claim is best describedby which of the following?(A) It questions the aptness of the analogy drawnby X.(B) It makes apparent Xs failure to consider howpeople

38、vary in their responses to a seriousaccident.(C) It shifts the basis for judging rationality toconsiderations of utility.(D) It offers an alternative explanation of whypeople form incorrect beliefs.(E) It challenges Xs assumption that the occur-rence of a single event is sufficient to changea belief

39、.8.John: It is permissible and even advisable toexecute criminals convicted of brutalmurders. After all, a publicized executioncan serve to deter heinous crimes and thusminimize suffering in the long run. Capital.punishment is a kind of societal self-defense.Mary: You are ignoring the prior issue of

40、 whethera state or society has the right to takeanyones life. If there is no such right. then,the issue of whether capital punishmentdeters crime is irrelevant.If it were determined dial capital punishment doesnot serve to deter crime. Johns and Marys posi-tions would be affected in which of the fol

41、lowingways?(A) Neither Johns nor Marys position would beaffected.(B) Both Johns and Marys positions would beweakened.(C) Marys position would be strengthened butJohns position would not be affected.(D) Johns position would be weakened but Marysposition would not be affected,(E) Johns position would

42、be weakened and Marysposition would be strengthened.9. Excluding purchases by businesses, the averageamount spent on a factory-new car has risen 30 per-cent in the last five years. In the average householdbudget, the proportion spent on car purchases hasremained unchanged in that period. Therefore t

43、heaverage household budget must have increased by30 percent over the last five years.Which of the following is an assumption on whichthe argument relies？(A)The average number of factory-new cars pur-chased per household has remained unchangedover the last five years.(B)The average amount spent per c

44、ar by businessesbuying factory-new cars has risen 30 percent inthe last five years.(C)The proportion of the average household budgetspent on all car-related expenses has remainedunchanged over the last five years.(D)The proportion of the average household budgetspent on food and housing has remained

45、unchanged over the last five years.(E)The total amount spent nationwide on factory-new cars has increased by 30 percent over thelast five years.10. Editorial：Critics of nuclear power complain about the allegedlyserious harm that might result from continued operationof existing nuclear power plants.

46、But such concerns donot justify closing these plants；after all, their operationhas caused no more harm than that caused by pollutiongenerated by coal-and oil-burning power plants, themost important other sources of energy.Which of the following is an assumption on which theargument depends？(A) Exist

47、ing nuclear power plants should be closed onlyif it can be conclusively demonstrated that theircontinued operation is likely to cause harm moreserious than the harm their operation has alreadycaused.(B) Closing existing nuclear power plants would requiregreatly increased reliance on coal-and oil-bur

48、ningpower plants.(C) The harm that has resulted from operation ofexisting coal and oil-burning power plants hasbeen significant.(D) The harm that a nuclear power plant is likely tocause as it continues to operate can be reliablypredicted from the past history of nuclear powerplants.(E) The only harm

49、 that has resulted from operation ofexisting coal and oil-burning power plants hasresulted from the pollution generated by theseplants.(F) Closing existing nuclear power plants would requireincreased reliance on coal-and oil-burning powerplants.11. Sleep deprivation is a known cause of workplaceerro

50、r, and many physicians frequently go withoutsleep for periods of 24 hours or more. However, fewof these physicians have, in the course of a routineexamination by a peer, been diagnosed with sleepdeprivation. So there is little cause for concern thathabitual sleep deprivation will cause widespreadphy

51、sician error.The answer to which of the following questionswould be most helpful in evaluating the argument？(A)Do physicians who have been diagnosed withsleep disorders also show signs of other ills notrelated to sleep deprivation？(B)Is the ability to recognize the symptoms of sleepdeprivation in ot

52、hers significantly impaired byhabitual sleep deprivation？(C)Do factors other than habitual sleep deprivationever lead to errors in the workplace on the partof physicians？(D)Of people who have recently been treated byphysicians, what percentage believe that manyphysicians have occasionally suffered f

53、rom sleepdeprivation？(E)Is the incidence of sleep deprivation higheramong physicians than it is among other healthcare workers？12. The organizers of tomorrows outdoor concertannounced that it will go on tomorrow on scheduleunless bad weather is forecast or too few advancetickets are sold. If the con

54、cert is canceled, refundswill be made to ticket holders. Since some ticketholders have already been issued refunds even thoughmore than enough advance tickets were sold, it mustbe the case that bad weather is forecast.Which of the following is an error of reasoningcontained in the argument?(A) It pr

55、oceeds as if a condition, which by itself isenough to guarantee a certain result, is the onlycondition under which that result would occur.(B) It bases athat is known to requiretwo conditions on evidence that bears on onlyone of those conditions.(C) It explains one event as being caused by anotherevent, even though both events must actuallyhave been caused by some third, unidentifiedevent.(D) It treats evidence for the absence of one conditionunder which a circumstance would occuras conclusive evidence that that circumstancewill not