GRE写作中类比类逻辑错误举例

　类比类逻辑错误(False analogy)

　　说到类比类逻辑错误，我们应先弄清楚什么是类比论证?类比证论是一种通过已知事物(或事例)与跟它有某些相同特点的事物(或事例)进行比较类推从而证明论点的论证方法。其中，“相同特点”是这种论证方法能够成立的前提，没有它，就无法进行类推;“比较类推”是这种论证方法的根本标志，没有这个推理过程，就达不到证明论点的目的;“已知事物”是这种论证方法的一个重要条件，它是为所要论述的主体事物服务的客体事物，没有这个条件，不能使类推的道理明显化，不易为读者接受，在某些情况下也不能达到证明论点的目的。这种论证方法通过客体事物与主体事物相同特点的比较，把客体事物的性质类推到主体事物上，由此揭示出主体事物具有客体事物同样的性质，从而达到证明论点的目的。

　　但是在argument作文中，通常是不给出类比的前提条件，只是通过一个条件，作者就得出相同的结论。如在A地方发生的情况，作者就很容易的得出结论，即在B地方也必然发生相同的情况。这也正是argument作文中类比错误常见的出题方式。在比较两个事物的相似性时，只看到了它们表层的共性，而忽略了它们深层的差异。因此，对于这类型的逻辑错误，我们在写的时候就应该重点找出它们深层的差异，作为攻击的突破点。

　　下面就以一个具体的因果关系错误来说明：

　　The following appeared in a letter sent by a committee of homeowners from the Deer haven Acres to all homeowners in Deer haven Acres.

　　"Seven years ago, homeowners in nearby Brookville community adopted a set of restrictions on how the community"s yards should be landscaped and what colors the exteriors of homes should be painted. Since then, average property values have tripled in Brookville. In order to raise property values in Deer haven Acres, we should adopt our own set of restrictions on landscaping and house painting."

　　【译文】

　　“ 七年前，附近的Brookville社区的业主实施了一系列关于该社区的庭院应如何布置以及房屋应涂何种颜色的规定。从那以后，Brookville的地产平均价格翻了三番。为使Deer haven Acres的地产升值，我们也应该对于景观和房屋涂色实施自己的规定。”

　　【分析】

　　这个题目中存在着一个很明显的类比错误，即在上文中提到的“在A地方发生的情况，在B地方也必然发生”。文中说，Brookville城市通过规定房屋颜色取得了成功，因此，Deer haven Acres城市可以通过同样的方法实现同样的目的。这是一个十分典型的错误类比。这两个城市的相似性很可能仅在于它们都是城市而已;如果 Brookville地方拥有非常便利的交通，人们都愿意在此购房，而Deer haven Acres根本没有如此便利的交通资源，那么简单地效仿显然是不明智的。即便Brookville通过规定房屋颜色取得了成功，但是同样的做法未必在 Deer haven Acres地方取得相同的效果。论断没有两地间的交通、功能以及住户特点等问题比较异同，因此，这样做出的结论显得匆促。

　　在写argument逻辑错误时，常用的论证语句有：

　　1、The reason /argument rests on the assumption that A is analogous to / similar to B in all respects.

　　2、This assumption is weak, since although there are points of comparison between A and B, there are much dissimilarity as well.

　　3、The author also commits the fallacy “all things are equal”

　　4、The fact that happened two years ago is not a sound evidence to draw a conclusion that…..

　　5、 The author assumes without justification that the background conditions have remained the same at different times or at different locations.

　　6、However, it is not clear in this argument whether the current conditions at A are the same as they used to be two years ago.

　　7、Thus it is impossible to conclude that….

　　下面是根据上面的题目写出的类比类逻辑错误：

　　Even assuming that Brookville’s rising property values are attributable to the implementation of these restrictions, the committee fails to consider possible differences between Brookville and Deer haven Acres that might help to bring about a different result for Deer haven Acres. For instance, potential home-buyers might be less interested in a home’s exterior appearance than Brookville home-owners. For that matter, perhaps Deer haven Acres home-buyers would find consistent Deer haven Acres property values. Without accounting for these and other possible dissimilarities, the committee cannot assume that what resulted in rising property values in Brookville would bring about the same result in Deer haven Acres.