FeiFei逻辑第50题--看不懂正确选项，求教

ustchero

Questions 49-50

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Laura: Your encyclopedia is out of date.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.   （C）

(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.

凭感觉做对了题，但是甚至看不明白C选项的意思

请NN给解释一下

不胜感激

ustchero

顶一下，急啊

lift1217

看题目和选项一头雾水，你要不说答案是C，我十有八九得做错，看了足有5分钟，试着解释一下：C 的意思应该是：把推出结论需要的东西当作能确保结论的东西，可以理解为把必要条件当作充分条件吗？我从来没有做过类似总结性的东西，所以不知道。放到题目里应该是：要证明Fermat没有撒谎或搞错，仅仅Fermat’s theorem 被证明了是不够的，

遥遥G梦

To prove that Fermat did not lie, it is necessary to know that the theory is provable,but being provable can not ensure that he told the true. However, Laura came up with the conclusion anyway. Hence, she make the mistake stated in C. 

joanna0630

我的翻译是

她将（1结论存在所必须的条件）和（2要确保结论存在所需的充分条件）相混淆了。

mistake(1)for(2)

清韵流音LY

Laura说，因为P的结论已经被证明了，所以J说P不能被证明这个说法是不对的。可是我们知道，结论被后人证明是对的 不能表明P就自己证明了。所以这是充分条件和必要条件搞混了——p自己证明是对的=>结论是对的。而反之不成立。C的意思就是这样，翻译成充分条件和必要条件就对了。

ba1a糖儿

两人的逻辑：
theory未被证实——》T错或者说谎（when he claim）
被别人证实了——》T没有错也没说谎

也许T就随口一说——说谎了，而后人恰巧证明了这个“说”是正确的
=>
不能说明T没错/说谎

所以C：她搞错了“对结果很重要的一个事”（被证明）vs“可以得出结论的一个事”（T没有说谎也没有错）