淺談‘邏輯法’在托福閱讀‘推理題’中的應用

推理題（Inference Questions）與上一篇文章之中的‘修辭目的題’同為側重邏輯關系考察的題目，也就是說，本系列文章第一篇中的‘六大主干邏輯’也是解決推理題的關鍵。

話題一：推理題的識別

推理題一般題目中會出現(xiàn)兩個標志性的詞：infer（推斷）和imply（暗示），如What can be inferred from the claim that…?

What does the author imply about XXX?

話題二：推理題的邏輯解題

推理題其實是屬于細節(jié)題的一種，于是適用于細節(jié)題的定位法同樣適用于推理題；由于定位法是以前的講座內(nèi)容，在此不再贅述。我沒來看定位之后的邏輯推理過程。

ETS為了保證實體的規(guī)范和標準化，推理題一般只有正向推理和負向推理兩種。

正向推理：即答案信息和文中所給信息為同義轉述。正向推理一般對應以下幾種邏輯：

1. 同理類比關系

同理類比經(jīng)常出現(xiàn)like, same, similar, likewise等標志，顧名思義，同理類比即表示兩者比對象相似，于是，根據(jù)對象A，可以同理推得對象B。

比如：像小明一樣，小峰很高。

問題：關于小明可以推斷到什么？

答案：小明很高（通過‘像’字，體現(xiàn)兩者相似之處，進而由小峰同理推得小明的情況）。

2. 總分/舉例關系

由于例子和細節(jié)是用來支持總體規(guī)律的，所以總體規(guī)律的特點例子和細節(jié)一定也滿足。換句話說，一般是‘由總推到分’的方向。

比如：中國冬天很多北風。北京坐落在中國北方。

問題：關于北京可以推斷到什么？

答案：北京冬季有很多北風（中國冬季多北風，而北京屬于中國的一部分，即總分關系，于是可以同向推得，北京冬季也多北風）

負向推理：即答案信息與文中所給信息為反義轉述。負向推理涉及邏輯如下：

1. 正反對比關系

經(jīng)常出現(xiàn)unlike, different, on the contrary等標志，顧名思義，同理類比即表示兩者比對象相反，于是，一直對象A，可以反義推得對象B。

2. 新的時間點出現(xiàn)

新的時間點出現(xiàn)一般標志著描述新的情況，所以，時間點的前后的情況一般相反。于是，我們可以逆向推理時間點前后的內(nèi)容。

比如：他現(xiàn)在是個好學生。

時間點‘現(xiàn)在’標志著前后相反，所以可以推斷到，他以前不是個好學生。

3. 新的地點出現(xiàn)

是‘新的時間點’導致的相反類似，新的地點出現(xiàn)也標志著新的情況出現(xiàn)。所以同樣可以判斷新提到的地點和前面提到的地點不同。

比如：青海老家找不到工作，于是他們來到了浙江。

新地點‘浙江’出現(xiàn)，標志著浙江的情況和青海不同，于是推斷到，浙江找得到工作。

真題應用：

Paragraph 1: It should be obvious that cetaceans-whales, porpoises, and dolphins-are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke3 and blowhole cannot disguise their affinities with land-dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but, already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.

1. Which of the following can be inferred from paragraph 1 about early sea otters?

○It is not difficult to imagine what they looked like

○There were great numbers of them.

○They lived in the sea only.

○They did not leave many fossil remains.

邏輯解題應用：

根據(jù)定位法，通過關鍵詞sea otters可以快速定位到文中第四五行交界處，根據(jù)句中邏輯關系詞unlike可知，sea otters和first whales應該為正反對比/相反關系。于是，根據(jù)first whales做逆向推斷，即可得到A選項。

Paragraph 2: Nearly any kind of plant of the forest understory can be part of a deer's diet. Where the forest inhibits the growth of grass and other meadow plants, the black-tailed deer browses on huckleberry, salad, dogwood, and almost any other shrub or herb. But this is fair-weather feeding. What keeps the black-tailed deer a lived in the harsher seasons of plant decoy and dormancy? One compensation for not hibernating is the built- in urge to migrate. Deer may move from high-elevation browse areas in summer down to the lowland areas in late fall. Even with snow on the ground, the high bushy understory is exposed; also snow and wind bring down leafy branches of cedar, hemlock, red alder, and other arboreal fodder.

2.  It can be inferred from the discussion in paragraph 2 that winter conditions 

○ Cause some deer to hibernate 

○ Make food unavailable in the highlands for deer 

○ Make it easier for deer to locate understory plants 

  ○ Prevent deer from migrating during the winter

邏輯解題應用：

根據(jù)定位法，通過關鍵詞winter conditions可以快速定位到文中第四五行交界處harsher seasons of plant decoy and dormancy，但是本句無答案對應，于是繼續(xù)向后Deer may move from high-elevation browse areas in summer down to the lowland areas in late fall，可見新地點lowland areas出現(xiàn)，于是根據(jù)‘新地點相反’，可知high elevation browse areas與‘lowland areas冬季有食物吃’應為相反，故為‘高地冬季無食物’。B正確。

Paragraph 2: This was before the steam locomotive, and canal building was at its height. The companies building the canals to transport coal needed surveyors to help them find the coal deposits worth mining as well as to determine the best courses for the canals. This job gave Smith an opportunity to study the fresh rock outcrops created by the newly dug canal. He later worked on similar jobs across the length and breadth of England, all the while studying the newly revealed strata and collecting all the fossils he could find. Smith used mail coaches to travel as much as 10,000 miles per year. In 1815 he published the first modern geological map, “A Map of the Strata of England and Wales with a Part of Scotland,” a map so meticulously researched that it can still be used today.

3. Which of the following can be inferred from paragraph 2 about canal building?

○ Canals were built primarily in the south of England rather than in other regions.

○ Canal building decreased after the steam locomotive was invented.

○ Canal building made it difficult to study rock strata which often became damaged in the process.

○ Canal builders hired surveyors like Smith to examine exposed rock strata.

邏輯解題應用：

按照定位法，通過關鍵詞canal building可以快速定位到文中第一句，根據(jù)新時間點before the steam locomotive，于是根據(jù)‘新時間點相反’，以及后句中的，可知steam locomotive出現(xiàn)之后與‘canal building was at its height’應為相反，即‘運河建造衰落’。B正確。

Paragraph 4: Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicefus. Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs.

4. It can be inferred that Basilosaurus bred and gave birth in which of the following locations

○On land

○B(yǎng)oth on land and at sea

○In shallow water

○In a marine environment

邏輯解題應用：

按照定位法，通過關鍵詞Basilosaurus可以快速定位到文中第2句，但是本句無答案對應，繼續(xù)向后讀，直到最后一句undoubtedly a fully marine whale中的fully與題目所問的bred and gave birth應為總分關系，根據(jù)正向推斷，可知bred and gave birth也應該滿足fully marine的特點。D正確。

Paragraph 5: Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. Once a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical
models of ecosystems likewise suggest that diversity does not guarantee ecosystem stability—just the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. (A fifteen-speed racing bicycle is more likely to break down than a child’s tricycle.)

5. Which of the following can be inferred from paragraph 5 about redwood forests?

○They become less stable as they mature.

○They support many species when they reach climax.

○They are found in temperate zones.

○They have reduced diversity during mid-successional stages.

邏輯解題應用：

按照定位法，通過關鍵詞redwood forests可以快速定位到文中第3行，根據(jù)句中出現(xiàn)的for example舉例邏輯標志，可知redwood forests應該屬于前句的例子，根據(jù)正向推斷，例子一定滿足前句原理的特點（即At least in temperate zones），可知redwood forests也在temperate zones。C正確。

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