直接反对前提是可以的吗？ＯＧ９６ＶＳＯＧ６８

96.
The difficulty with the proposed high-speed train line is that a used plane can be bought for one-third the price of the train line, and the plane, which is just as fast, can fly anywhere. The train would be a fixed linear system, and we live in a world that is spreading out in all directions and in which consumers choose the free-wheel systems (cars, buses, aircraft), which do not have fixed routes. Thus a sufficient market for the train will not exist.

Which of the following, if true, most severely weakens the argument presented above?

(A) Cars, buses, and planes require the efforts of drivers and pilots to guide them, whereas the train will be guided mechanically.
(B) Cars and buses are not nearly as fast as the high-speed train will be.
(C) Planes are not a free-wheel system because they can fly only between airports, which are less convenient for consumers than the high-speed train's stations would be.
(D) The high-speed train line cannot use currently underutilized train stations in large cities.　　（Ｃ）
(E) For long trips, most people prefer to fly rather than to take ground-level transportation.

这题：推倒过程：因为train不是free wheel system，而飞机是free wheel system－－－>结论：train将没有市场了．

　　　削弱：飞机不是free wheel system．

通过直接反对前提来削弱结论．

68.
A drug that is highly effective in treating many types of infection can, at present, be obtained only from the bark of the ibora, a tree that is quite rare in the wild. It takes the bark of 5,000 tree to make one kilogram of the drug. It follows, therefore, that continued production of the drug must inevitably lead to the ibora's extinction.

Which of the following, if true, most seriously weakens the argument above?

(A) The drug made from ibora bark is dispensed to doctors from a central authority.
(B) The drug made from ibora bark is expensive to produce.
(C) The leaves of the ibora are used in a number of medical products.
(D) The ibora can be propagated from cuttings and grown under cultivation.
(E) The ibora generally grows in largely inaccessible places.

推理：因为这种树非常少，而且制药所需的量又非常大．－－－>结论：继续生产这种药会使树灭绝．

对于Ｄ．我没有问题．

Ｅ：说这种树根本就是inaccessible．ＯＧ解释说无关。我也理解．可是我觉得这个不就是很类似于９６Ｃ的那种削弱方法吗？直接反对前提．　为什么９６Ｃ可以而６８Ｅ不可以呢？是不是６８Ｅ根本就不是前提？

晕了晕了。．请教ＮＮ．．

我明白你的意思，既然这个树人们都弄不到，肯定就不会拿来做药，也不会灭绝了。

但我觉得有一个假设：你咋知道它长在悬崖陡壁人们就弄不到呢。

此题结论是continued production lead to extinction.

WEAKEN就要指出  continued production 不会 lead to extinction.

D正好说明，因为繁殖能力超强，continued production 不会 lead to extinction.

而E， 说人们要搞到这个树很费劲，只能质疑continued production 能否实现。而且文中说if it follows,就是说continued production 可以实现吧。

顶一下。没人知道吗？请教．

可以反对

但是不是优先的选项

断桥 他因 因果互置 最后是直接反对前提  （好像AWA 管这个叫 质疑数据的有效性？？？）

哈哈

我也不是很清楚 allen0018(A) hotmail.com 咱们探讨吧

我觉得 除了削弱 别的都不能反对前提  不知道对不对

又想了下。偶觉得是一般型的结论是可以用反对前提的方法.也无所谓优先与否.只要能对结论起削弱作用就可以了。又如ＯＧ４３

43.

With the emergence of biotechnology companies, it was feared that they would impose silence about proprietary results on their in–house researchers and their academic consultants. This constraint, in turn, would slow the development of biological science and engineering.

Which of the following, if true, would tend to weaken most seriously the prediction of scientific secrecy described above?

A. Biotechnological research funded by industry has reached some conclusions that are of major scientific importance.

B. When the results of scientific research are kept secret, independent researchers are unable to build on those results.

C. Since the research priorities of biotechnology companies are not the same as those of academic institutions, the financial support of research by such companies distorts the research agenda.

D. To enhance the companies’ standing in the scientific community, the biotechnology companies encourage employees to publish their results, especially results that are important.  

E. Biotechnology companies devote some of their research resources to problems that are of fundamental scientific importance and that are not expected to produce immediate practical applications.

类似的还有OG96 170 14 　

而如果结论为条件型结论(if..then..),是绝对不可以反对前提的。削弱方法为:承认if.. 成立，而then．．不成立．

而ＯＧ６８这个，结论是继续生产导致植物灭绝．削弱就是继续生产不能导致植物灭绝．所以选Ｄ．不选Ｅ．

欢迎大家多讨论啊．．．

我也同意正确选项96是反对前提的说法

虽然不是最优，可是我们讨论的最优选项是在题目给出答案的范围内，而不是理论上的最优，C项是所有给定答案中最起weaken作用的，所以中奖

我觉得68的E答案并没有反对前提，前提是“a tree that is quite rare in the wild”

答案(E) The ibora generally grows in largely inaccessible places

前提说的是数量少，很少出现；但答案说的是生长在弄不到的地方，弄不到不代表数量少啊，并没有反对这个tree是一种稀少的tree. 所以解释说是无关的。

96的C答案除了反对了一下下前提，还有一个“方案有重大缺陷”的削弱，所以也不是单纯反对前提的。

欢迎讨论。

偶也觉得，如果在Arguement中，连推出结论的条件都是不真实或者错误的话，结论当然不能够成立，只要使arguement推理链中的某一环断掉，就算是削弱了。条件型结论除外