一道LR，谢谢

didiwei

2004.10

这道题的答案是E，请问C为什么不对，谢谢。

    

15. Artists have different ways of producing contours and hatching, and
analysis of these stylistic features can help to distinguish works by a
famous artist both from forgeries and from works genuinely by other
artists. Indeed, this analysis has shown that many of the drawings
formerly attributed to Michelangelo are actually by the artist Giulio
Clovio, Michelangelo's contemporary.


        
If the statements above are true, then which one of the following must
also be true?


        
A. Contours and hatching are the main features that distinguish the
drawing styles of different artists.


        
B. Many of the drawings formerly attributed to Michelangelo are actually
forgeries.

C. No forgery can perfectly duplicate the contour and hatching styles of
a famous artist.

D. The contour and hatching styles used to identify the drawings of
Clovio cited can be shown to be features of all Clovio's works.

E. There is an analyzable difference between Clovio's contour and
hatching styles and those of Michelangelo.

[此贴子已经被作者于2009-5-13 12:06:08编辑过]

crusoecrusoe

C. No forgery can perfectly duplicate the contour and hatching styles of
a famous artist.

原文analysis of these stylistic features can help to distinguish works，

即：A→ B，根据stylistic features  推 distinguish works。

No forgery can perfectly duplicate the contour and hatching styles of
a famous artist.

即：非B→非A，根据distinguish works（ forgery ） 推 非stylistic features。

做逆否命题，意味着是“因果关系”，而从文中不能看出。

（至少No是那么的绝对，在逻辑推理中应避免绝对，绝对容易导致前提非真，必然结论假）

didiwei

谢谢牛老大，我的formal logic不大好。
再请问一下，是不是只有因果关系才能推逆否命题，对于不是因果关系的陈述，推逆否命题也不一定对？

crusoecrusoe

是，因果关系，即满足“充分必要”，是充要条件，即可推逆否。

（因果关系标志词：A is due to B；A is result of B；blame B on/for A；B is responsible for A；credit A to B 等等。）

（本题事实上，看到No，就知排除了，毕竟世上无绝对）

crusoecrusoe

值得注意的是：

题干第二句：

“ Indeed, this analysis has shown that many of the drawings
formerly attributed to Michelangelo are actually by the artist Giulio
Clovio, Michelangelo's contemporary.”

“attributed to”也算是因果关系标志词，但问题在于，attributed to连接的并不是主要逻辑关系（the drawings
formerly attributed to Michelangelo 并非主要逻辑的A和B），所以这算得上是一个逻辑陷阱。

didiwei

啊？！不想不知道，一想吓一跳，里面有这么多文章。
谢谢crus 的耐心解释，你真是太nice了。