浅谈‘逻辑法’在托福阅读‘推理题’中的应用

推理题（Inference Questions）与上一篇文章之中的‘修辞目的题’同为侧重逻辑关系考察的题目，也就是说，本系列文章第一篇中的‘六大主干逻辑’也是解决推理题的关键。

话题一：推理题的识别

推理题一般题目中会出现两个标志性的词：infer（推断）和imply（暗示），如What can be inferred from the claim that…?

What does the author imply about XXX?

话题二：推理题的逻辑解题

推理题其实是属于细节题的一种，于是适用于细节题的定位法同样适用于推理题；由于定位法是以前的讲座内容，在此不再赘述。我没来看定位之后的逻辑推理过程。

ETS为了保证实体的规范和标准化，推理题一般只有正向推理和负向推理两种。

正向推理：即答案信息和文中所给信息为同义转述。正向推理一般对应以下几种逻辑：

1. 同理类比关系

同理类比经常出现like, same, similar, likewise等标志，顾名思义，同理类比即表示两者比对象相似，于是，根据对象A，可以同理推得对象B。

比如：像小明一样，小峰很高。

问题：关于小明可以推断到什么？

答案：小明很高（通过‘像’字，体现两者相似之处，进而由小峰同理推得小明的情况）。

2. 总分/举例关系

由于例子和细节是用来支持总体规律的，所以总体规律的特点例子和细节一定也满足。换句话说，一般是‘由总推到分’的方向。

比如：中国冬天很多北风。北京坐落在中国北方。

问题：关于北京可以推断到什么？

答案：北京冬季有很多北风（中国冬季多北风，而北京属于中国的一部分，即总分关系，于是可以同向推得，北京冬季也多北风）

负向推理：即答案信息与文中所给信息为反义转述。负向推理涉及逻辑如下：

1. 正反对比关系

经常出现unlike, different, on the contrary等标志，顾名思义，同理类比即表示两者比对象相反，于是，一直对象A，可以反义推得对象B。

2. 新的时间点出现

新的时间点出现一般标志着描述新的情况，所以，时间点的前后的情况一般相反。于是，我们可以逆向推理时间点前后的内容。

比如：他现在是个好学生。

时间点‘现在’标志着前后相反，所以可以推断到，他以前不是个好学生。

3. 新的地点出现

是‘新的时间点’导致的相反类似，新的地点出现也标志着新的情况出现。所以同样可以判断新提到的地点和前面提到的地点不同。

比如：青海老家找不到工作，于是他们来到了浙江。

新地点‘浙江’出现，标志着浙江的情况和青海不同，于是推断到，浙江找得到工作。

真题应用：

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.

逻辑解题应用：

根据定位法，通过关键词sea otters可以快速定位到文中第四五行交界处，根据句中逻辑关系词unlike可知，sea otters和first whales应该为正反对比/相反关系。于是，根据first whales做逆向推断，即可得到A选项。

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

逻辑解题应用：

根据定位法，通过关键词winter conditions可以快速定位到文中第四五行交界处harsher seasons of plant decoy and dormancy，但是本句无答案对应，于是继续向后Deer may move from high-elevation browse areas in summer down to the lowland areas in late fall，可见新地点lowland areas出现，于是根据‘新地点相反’，可知high elevation browse areas与‘lowland areas冬季有食物吃’应为相反，故为‘高地冬季无食物’。B正确。

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.

逻辑解题应用：

按照定位法，通过关键词canal building可以快速定位到文中第一句，根据新时间点before the steam locomotive，于是根据‘新时间点相反’，以及后句中的，可知steam locomotive出现之后与‘canal building was at its height’应为相反，即‘运河建造衰落’。B正确。

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

○Both on land and at sea

○In shallow water

○In a marine environment

逻辑解题应用：

按照定位法，通过关键词Basilosaurus可以快速定位到文中第2句，但是本句无答案对应，继续向后读，直到最后一句undoubtedly a fully marine whale中的fully与题目所问的bred and gave birth应为总分关系，根据正向推断，可知bred and gave birth也应该满足fully marine的特点。D正确。

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.

逻辑解题应用：

按照定位法，通过关键词redwood forests可以快速定位到文中第3行，根据句中出现的for example举例逻辑标志，可知redwood forests应该属于前句的例子，根据正向推断，例子一定满足前句原理的特点（即At least in temperate zones），可知redwood forests也在temperate zones。C正确。

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