请教一题bible上的LR

lindeman

这题看了答案没看明白。
vague laws set vague limits on people's freedom,which makes it impossible for them to know for certain whether their actions are legal. thus,under vague laws people cannot feel secure.


A.people can feel secure only if they know for certain whether their actions are legal.


B.if people do not know for certain whether their actions are legal,then they might nit feel secure.


C.if people know for certain whether their actions are legal, they can feel secure.


E.only people who feel secure can know for certain whether their actions are legal.


D是无关选项，就不列出了。
请教一下大家这题怎么做，错误选项为什么是错的。请赐教，谢谢。

sdcar2010

Premise: Vague laws --> impossible to be certain of legality
Conclusion: Vague laws --> not secure

The gap is between "impposible to be certain of legality" and "not secure". If the assumption is : impossible to be certain of legality --> not secure, the argument is complete. Answer choice A fits the bill, although it is in the countrapositive mode of the original assumption.

lindeman

thank you!
i failed to consider the negativity.

taoransk

Sdcar always provide the best answer ~

Bensontuo

首先吧, 下次貼題目, 請把題幹一起完整的post上來, 不然不知道題目到底在考什麼。

Anyway, 來看論證吧。

Vague law ---> Vague limit on people's freedom ---> Impossible to know whether their actions are legal.

Vague law ---> People can't feel secure.

我想題目不外乎考的就是加強 （ 必要假設 ), 削弱 （ 必要假設的取非, 或是必要假設的不必要情況是存在的）, 必定為真 （ 數學交集聯集, 或是必要條件）, 假設題型 （ 充分, 必要, infer )

" Impossible to know whether their actions are legal ---> People can't feel secure " = > " People can feel secure ---> possible to know whether their actions are legal "


看答案吧

如果Ａ是正確答案的話, 題目在考什麼？  必定為真, 必要假設, 加強

如果Ｂ是正確答案的話, 題目在考什麼？  可能為真, 可能不為真 （ 必定為真的” 除外 “ ）

如果Ｃ是正確答案的話, 題目在考什麼？   削弱

如果Ｅ是正確答案的話, 題目在考什麼？  ----> 根本無關原文論證