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标题: 狒狒锣既宝点地50题[求助] [打印本页]

作者: nan    时间: 2002-11-7 10:30     标题: 狒狒锣既宝点地50题[求助]

Joseph: my encyclopedia says that the mahematician Pierre de Fermat died in 1665 without leaving behind any wirtten prrof for a theorem that he claimed nontheless to have proved. Probably this alleged theorem simply can not be proved, since-as the article points out- no one esle has been able to prove it.
therefore it is likely that Fermat was either lying or esle 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Laura: your encyclopedia is out of date.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.
which one of the follwing 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 quality of a person's character can legitimately be taken on guarantee the accuracy of the claim that person has made.
c)it mistakes somethings that is necessary for its conclusion to follow for something that ensure that conclusion follows.
d)...
e)...

why the answer is C, i choose A??
作者: zyh79    时间: 2002-11-7 13:12

Joseph:因为没人能证明,所以撒谎
      没人能证明是撒谎的充分条件
      撒谎是没人能证明的必要条件
所以, 能证明是不撒谎的必要条件,而不是充分条件
Laura:能证明可推出不撒谎,颠倒了充分必要性。简单地说,就算能证明,也未必可以保证不撒谎 。
作者: nan    时间: 2002-11-7 19:43

still confused!
作者: zyh79    时间: 2002-11-7 20:16

一句话:
不能证明,所以撒谎
并不能推出:能证明,所以不撒谎




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