[整理]feifei-21

Terryn

feifei-21

21. Historian: We can learn about the medical history of individuals through chemical analysis of their hair. It is likely, for example, that Isaac Newton’s psychological problems were due to mercury poisoning; traces of mercury were found in his hair. Analysis is now being done on a lock of Beethoven’s hair. Although no convincing argument has shown that Beethoven ever had a venereal disease, some people hypothesize that venereal disease caused his deafness. Since mercury was commonly ingested in Beethoven’s time to treat venereal disease, if researchers find a trace of mercury in his hair, we can conclude that this hypothesis is correct.

Which one of the following is an assumption on which the historian’s argument depends?

(A) None of the mercury introduced into the body can be eliminated.
(B) Some people in Beethoven’s time did not ingest mercury.
(C) Mercury is an effective treatment for venereal disease.
(D) Mercury poisoning can cause deafness in people with venereal disease.
(E) Beethoven suffered from psychological problems of the same severity as Newton’s.

http://forum.chasedream.com/LSAT/thread-105261-1-1.html?SearchText=feifei%2021
Option D undermines the conclusion that venereal diseases caused Benthoveen's deafness.

The structure of the stimulus:

Premise 1: Mercury has been found in the lock of Benthoveen's hair;

Premise 2: In Benthoveen's time, mercury is commonly used to treat venereal diseases;

Conclusion: Venereal diseases caused Benthoveen's deafness.

The argument, in my opinion, makes at least three assumptions: (1) Mercury trace found in B's hair must caused by treatment of venereal disease; (2) If someone ingests mercury, they must be used to treat venereal disease; (3) Except venereal disease, the other diseases cannot caused deafness.

Option B is a transformation of the second assumption mentioned above.

http://forum.chasedream.com/GMAT_CR/thread-17525-1-1.html

来这样看看取反的过程，希望有助于理解：
(B) Some people in Beethoven’s time did not ingest mercury.

取反：Some => None; 句子变成：
None of people in Beethoven’s time did not ingest mercury.

到这里可以理解吗? 好往下来：
句子中有一个 None, 后面有接了一个 Not; None ... Not 不就是 All 吗？所以取反会得到：
All people in Beethoven's time ingested Mercury.希望有帮助。

这是lsat中典型的逻辑游戏，你可能是钻入牛角尖了。

some people hypothesize that venereal disease caused his deafness. （要证明的假设）Since mercury was commonly ingested in Beethoven’s time to treat venereal disease,（证据）   if researchers find a trace of mercury in his hair, we can conclude that this hypothesis is correct. （结论）

其实，这题很简单：只需在证据和结论中间找到一个桥梁，这个强梁就是作者推论所依据的假设：即：在那个时代确实有人注射水银。
但是，those test maker不像我们正常人一样直接说：Some people in Beethoven’s time did ingest mercury. 他却说：Some people in Beethoven’s time did not ingest mercury！！很迷惑是吧。

其实两者是等价的

Some people in Beethoven’s time did ingest mercury.== Some people in Beethoven’s time did not ingest mercury

这是逻辑假言判断对当关系中的下反对关系，即上述两者不能同假，但可以同真。其推倒，要用到逻辑假言判断的差等关系与矛盾关系。如果你有兴趣可以参看以下面一个帖子的有关内容。
http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=17023

freegirl, 千万不可沉迷于logic game中，gmat是极少考这种logic game。要说在碰到这种题如何处理：只须记住：Some people in Beethoven’s time did ingest mercury.== Some people in Beethoven’s time did not ingest mercury。 出题人只不过是拐了个弯而已。

fyhllj

http://forum.chasedream.com/GMAT_CR/thread-184067-1-1.html?SearchText=feifei%2021

找到了大牛的讨论。http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=17525

B取非应该是用下面的方法。

全称肯定 (Everybody Did) 和特称否定(Somebody Did NOT)是矛盾关系
               
全称否定(Everybody did NOT=nobody did) 和特称肯定(Somebody did)是矛盾关系。

hanlei8492

feifei-21
B取非应该是用下面的方法。
全称肯定 (Everybody Did) 和特称否定(Somebody Did NOT)是矛盾关系
             
全称否定(Everybody did NOT=nobody did) 和特称肯定(Somebody did)是矛盾关系。

-- by 会员 Terryn (2010/3/20 16:47:37)

这个解释好！