linlin的逻辑！谢谢！

linlin315

1、x-ray examination of a recently discovered painting--judged by some authorities to be a self-portrait by Vincent van Gogh--revealed an underimage of a woman's face. either van Gogh or another painter covered the first painting with the portrait now seen on the surface of the canvas. because the face of the woman in the underinage also appears on canvases van Gogh is known to have painted, the surface painting must be an authenic self-portrait by van Gogh.
the conclusion above is properly drawn if which of the following is assumed?
B. many painted canvases that can be reliable attributed to van Gogh contain underinages of subjects that appear on at least one other canvas that van Gogh is known to have painted.
c. any painted canvas incorrectly attibuted to van Gogh would not contain an underimage of a subject that appears in authentic paintings by that artist.
d. a painted canvas cannot be reliably attibuted to an artist unless the authenticity of any underimage that painting might contain can be reliably attibuted to the artist.
答案是C
C我明白！但是为什么B和D不对呢？若对B取非的话不就是许多已经被确认为示梵高的表面画都不包含有底影。不是一个很好的削弱吗？为什么不对呢！还有D为什么不对！！
2、a thorough search of Edgar Allan Poe's correspondence has turned up not a single letter in which he mentions his reputed morphine addicition. On the bases of this evidence it is dafe to say that Poe's reputation for having been a morphine addict is undeserved and that reports of his supposed addicition are untrue.
which of the following is assumed by the argument above?
d.Poe would have been unable to carry on an extensive correspondence while under the influence of morphine.
e.fear of the consequences would not have prevented Poe from indicating in his correspondence that he was addicted to morphine.
答案是：E
E我明白！我的问题是：书上说D对上述推理起到了支持作用。我怎么看不出来呢？？怎么支持的呀？？

mindfree

1. B的错误在many. 取非后不是exclusive. 既很多都没有下面的那幅画, 但是没有排除有的情况.如果是all, 取非就对了.所有的都没有, 原结论就错. 你说的削弱是没有错, 因为削弱不需要是必要条件或充分条件, 但是assumption必须是必要条件.

D最好是用排除法. 你要注意到这部分"authenticity of any underimage that painting might contain can be reliably attibuted to the artist". 文章并没有提到authenticitiy of underimage can be reliably attributed to VG. 这里存在一个gap! 正确答案中也只是说appear.

2. D有一定的的支持,但是如果是问support, 我感觉D也不是正确答案, 因为原文没有提到"extensive". 去掉extensive就是support, 如果爱伦坡有吗啡addiciton的话, 他就写不了信了.原文既然说他有书信, 那么D就是支持.

linlin315

以下是引用mindfree在2003-5-4 23:43:00的发言：
1. B的错误在many. 取非后不是exclusive. 既很多都没有下面的那幅画, 但是没有排除有的情况.如果是all, 取非就对了.所有的都没有, 原结论就错. 你说的削弱是没有错, 因为削弱不需要是必要条件或充分条件, 但是assumption必须是必要条件.

linlin315

以下是引用mindfree在2003-5-4 23:43:00的发言：
D最好是用排除法. 你要注意到这部分"authenticity of any underimage that painting might contain can be reliably attibuted to the artist". 文章并没有提到authenticitiy of underimage can be reliably attributed to VG. 这里存在一个gap! 正确答案中也只是说appear.

linlin315

以下是引用mindfree在2003-5-4 23:43:00的发言：
2. D有一定的的支持,但是如果是问support, 我感觉D也不是正确答案, 因为原文没有提到"extensive". 去掉extensive就是support, 如果爱伦坡有吗啡addiciton的话, 他就写不了信了.原文既然说他有书信, 那么D就是支持.