一道逻辑题。。

skipp

[size=14.007px]A proposed change to federal income tax laws would eliminate deductions from taxable income for donations a taxpayer has made to charitable and educational institutions. If this change were adopted, wealthy individuals would no longer be permitted such deductions. Therefore, many charitable and institutions would have to reduce services, and some would have to close their doors.
[size=14.007px]The argument above assumes which of the following?
[size=14.007px](A) Without incentives offered by federal income tax laws, at least some wealthy individuals would not donate as much money to charitable and educational institutions as they otherwise would have.
[size=14.007px](B) Money contributed by individuals who make their donations because of provisions in the federal tax laws provides the only source of funding for many charitable and educational institutions.
[size=14.007px](C) The primary reason for not adopting the proposed change in the federal income tax laws cited above is to protect wealthy individuals from having to pay higher taxes.
[size=14.007px](D) Wealthy individuals who donate money to charitable and educational institutions are the only individuals who donate money to such institutions.
[size=14.007px](E) Income tax laws should be changed to make donations to charitable and educational institutions the only permissible deductions from taxable income.
[size=14.007px]

[size=14.007px]这道题之前就有人讨论过，但我还是有点问题。。。
[size=14.007px]答案是A
[size=14.007px]逻辑链：减免的政策取消——富人总捐款减少——慈善机构活不下去了。。

A取反的话就是说，至少有一部分的富人会继续捐款。。。但言外之意不就是：还是会有富人少捐款？
那么富人总的捐款数还是会减少，这样没有削弱呀？

D选项 有的人说有only就排了，太粗暴了吧
有的人说D取反的话就是：富人不是唯一的捐款者，但总捐款还是会减少，所以没有削弱原文。
但这样的解释不就跟A一样的了吗？？？

skipp

自己顶一下~~~

skipp

有人吗。。。

skipp

小灰灰养大鸟

A取反的意思是：没有富人会不和原来捐款一样多，那总捐款不会减少，就是weaken了原文了。
At least some：至少有一些——取反是none：没有

其实Lz的逻辑链就已经没问题了呀：
逻辑链：减免的政策取消——富人总捐款减少——慈善机构活不下去了
中间的这个就是你为了从Premise（减免政策取消）推导Conclusion（慈善机构活不下去）做出的Assumption，填满了Gap。

D的问题在于，没有B的Assumption（也就是说富人的确会因为减免政策的取消而减少捐款）的前提下，富人是不是唯一的捐款者并不重要。
就算你取非：富人不是慈善机构的唯一捐款者。
这对于Premise（减免政策取消）--> Conclusion（慈善机构活不下去) 不能weaken啊!

小灰灰养大鸟

你预设的“总捐款还是会减少”也正是这个Argument的Assumption

skipp

小灰灰养大鸟 发表于 2017-10-17 17:18
你预设的“总捐款还是会减少”也正是这个Argument的Assumption

好的好的~~

danyuchn

AT LEAST SOME wealthy individuals WOULD NOT donate as much 的邏輯取反不是只有把NOT拿掉，而是變成ALL...WOULD...

e.g.
「這社會至少有一些人不守法」的反面不是「這社會至少有一些人守法」
（有沒有發現這兩句話不衝突？那怎麼會是取反）
反面應該是「這社會所有的人都守法」。

所以樓主A選項沒有看出錯誤的原因，其實是取反時沒有注意到頻率辭或集合比率範圍詞。
這個在CR Bible裡面有特別講到的，可以參考。

skipp

danyuchn 发表于 2017-10-18 16:13
AT LEAST SOME wealthy individuals WOULD NOT donate as much 的邏輯取反不是只有把NOT拿掉，而是變成ALL. ...

好的好的，完全明白啦~~感谢~