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求助一道费费逻辑题T-3-50

 

Joseph: My encyclopedia says that the mathematician Pierre de Fermat died in 1665 without leaving behind any written proof for a theorem that he claimed nonetheless to have proved. Probably this alleged theorem simply cannot be proved, since---as the article points out---no one else has been able to prove it. Therefore it is likely that Fermat was either lying or else mistaken when he made his claim.

Laura: Your encyclopedia is out of date. Recently someone has in fact proved Fermat’s theorem. And since the theorem is provable, your claim---that Fermat was lying or mistaken---clearly is wrong.

50. Which one of the following most accurately describes a reasoning error in Laura’s argument?

 

 

A.        It purports to establish its conclusion by making a claim that, if true, would actually contradict that conclusion.

B.        It mistakenly assumes that the quality of a person’s character can legitimately be taken to guarantee the accuracy of the claims that person has made.

C.        It mistakes something that is necessary for its conclusion to follow for something that ensures that the conclusion follows.

D.       It uses the term “provable” without defining it.

E.        It fails to distinguish between a true claim that has mistakenly between believed to be false and a false claim that has mistakenly been believed to be true.

答案是C,但是B为什么不对?

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把这个帖子顶起来,也是想知道为什么B不对。

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说一下我的理解吧,一点浅见,如有不当还请牛人更正!

B说Laura’s argument错误地假定一个人的人品可以合理地用来确保他所作出的言论的准确性

Laura的推理逻辑是:有人证明出来那个theoram了,因此Joseph的结论是错的——也就是Fermat没有撒谎,他确实证明了那个theoram.
 L的推理跟人品(
the quality of a person’s character)没有关系。
(F人品好,也不能由别人证明出他的结论推出他自己也证明出了他的结论;人品不好,也同样道路。)

题干要求找出L的推理错误,他的推理错误就是用一个必要条件来当作充分条件用:必要条件:F能证明他的结论推出别人也能证明他的结论。而要想F证明了他的结论,除了别人证明出了他的结论之外还需要别的证据来支持,单单一个条件不能得出F过去已经证明了他的结论

C指出了L的推理环节上的错误,而B跟L的推理无关

个人认为做这道题的关键就是牛牛们经常强调的:一定要搞清楚在什么前提下得出了什么结论,也就是他的推理过程,就把注意力集中在L通过什么证据得出了什么结论

罗嗦了一大堆,也不知道说清楚了没有。

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