一道让我困惑的题？

bigmouse

4. Only if the electorate is moral and intelligent will a democracy function well.
Which one of the following can be logically inferred from the claim above?
(A) If the electorate is moral and intelligent, then a democracy will function well.
(B) Either a democracy does not function well or else the electorate is not moral or not intelligent.
(C) If the electorate is not moral or not intelligent, then a democracy will not function well.
(D) If a democracy does not function well, then the electorate is not moral or not intelligent.
(E) It cannot, at the same time, be true that the electorate is moral and intelligent and that a democracy will not function well.
answer:C my choice
我觉得是D，因为它是原命题的逆否命题，而答案为什么是C，他不是原命题的否命题吗？他与原命题不等价吧？谢谢各位大牛帮忙看看。[em00]

StephanieYun

你是不是再看看题目阿， 原命题和逆否命题是不是那样？











生活是一杯清茶

bigmouse

还是比较困惑，原文的意思是只要选民是道德的并且是聪明的，那么民主就是运行得很好！那么它的逆否命题是：如果民主运行得不好，那么选民就是不道德或不聪明的！对不对？

atongmu

以下是引用bigmouse在2003-8-15 10:38:37的发言：
还是比较困惑，原文的意思是只要选民是道德的并且是聪明的，那么民主就是运行得很好！那么它的逆否命题是：如果民主运行得不好，那么选民就是不道德或不聪明的！对不对？

你对only if的理解有误。only if 是必要条件。

bigmouse

oh! my god! I'm very stupid! Thanks for atongmu!