请问···因果关系中也有充分必要条件这个说法吗？？

rx_11

RT

今天做题，直接晕了。

FEIFEI 的45题和50题

45. Commissioner: Budget forecasters project a revenue shortfall of a billion dollars in the coming fiscal year. Since there is no feasible way to increase the available funds, our only choice is to decrease expenditures. The plan before you outlines feasible cuts that would yield savings of a billion dollars over the coming fiscal year. We will be able to solve the problem we face, therefore, only if we adopt this plan.

This reasoning in the commissioner’s argument is flawed because this argument  
(A) relies on information that is far from certain
(B) confuses being an adequate solution with being a required solution
(C) inappropriately relies on the opinions of experts
(D) inappropriately employs language that is vague
(E) takes for granted that there is no way to increase available funds

答案是B


Joseph: My encyclopedia says that the mathematician Pierre de Fermat died in 1665 without leaving behind any written proof for a theorem that he claimed nonetheless to have proved. Probably this alleged theorem simply cannot be proved, since---as the article points out---no one else has been able to prove it. Therefore it is likely that Fermat was either lying or else mistaken when he made his claim.

Laura: Your encyclopedia is out of date. Recently someone has in fact proved Fermat’s theorem. And since the theorem is provable, your claim---that Fermat was lying or mistaken---clearly is wrong.

50. Which one of the following most accurately describes a reasoning error in Laura’s argument? C
(A) It purports to establish its conclusion by making a claim that, if true, would actually contradict that conclusion.
(B) It mistakenly assumes that the quality of a person’s character can legitimately be taken to guarantee the accuracy of the claims that person has made.
(C) It mistakes something that is necessary for its conclusion to follow for something that ensures that the conclusion follows.
(D) It uses the term “provable” without defining it.
(E) It fails to distinguish between a true claim that has mistakenly between believed to be false and a false claim that has mistakenly been believed to be true.

答案是C.

看了这两题的解释之后，我更是觉得两道题的错误都是在说因果关系中的充分和必要条件混淆。。可是我似乎是没有印象有这种说法：因果关系中也有充分何必要条件。条件关系中有充分和必要条件是肯定的，但是因果关系中有充分和必要条件好像就奇怪了啊。。。我查了POWERSCORE LSAT LOCIC BIBLE这本书也没有这么说过。。所以有没有人能告诉我呢????

fjatpku

a是b的唯一原因 则b是a的充分条件
a是b的充分原因 则a是b的充分条件
恩就想到这么多了

rx_11

 我可能说的太抽象了。。。简化一下

如果有下列因果关系成立：
CAUSE                                 EFFECT

   A--------------------------------> B      


那么是否有：


非B--------------------------------->非A




求解····

rx_11

另外，是否有



A       不一定能推出     非B


和


非B    不一定能推出     A



如果有上述结论的话，那因果关系和条件关系居然是一样的啊。。。。。    我好晕啊。。为什么逻辑书上不说明呢。。。

babyheather

楼主你也把我绕晕了~不要教条化呀~考试做题时你就好好分析题目所告之你的所有信息就行~
我觉得因果关系就是条件关系的一种形式啊~因果关系是什么？是必然的引起和被引起的关系，即有原因A就一定有结果B。这和题目中告诉你“如果A则B”当然是一样的。

sloop21

因为A，所以B,
则A是B的充分条件，B是A的必要条件。

rx_11

因为A，所以B,
则A是B的充分条件，B是A的必要条件。

-- by 会员 sloop21 (2010/4/27 11:32:26)

NO,I DON'T THINK SO...
我昨天终于看了N久的逻辑学才终于搞懂。。。
我以前也是这么认为的。。其实不是！！！！！只有条件中才有这个关系

即

IF  A  .....THEN  B

A才是B的充分条件，B才是A的必要条件。

而因果关系不存在充分必要条件。我前几天一直陷入这个坑怎么跳都跳不出来。。后来才懂了。。

因果关系中你就就事论事就可以了。。即证明A不一定是B的唯一原因，也就是证明还有别的原因可能造成B。。。但这个充分必要没有关系。。哎。。。我就是做这两道题被搅昏的。。其实这两道题都是想说明一个问题，就是还有别的原因可以造成B。。。（所以论坛上很多人的解释不可相信啊！！！他们也是昏的。。你一定要相信自己！！！）

fjatpku

恩就是这样的   causal relation里有各种多因一果一因多果之类的情况

sloop21

我觉得主要问题是，我们同时使用中文和英文才造成了这种矛盾。你能举个因果关系的例子吗？

babyheather

因为A，所以B,
则A是B的充分条件，B是A的必要条件。

-- by 会员 sloop21 (2010/4/27 11:32:26)

这个最基本的结论并不和“一因多果或一果多因”的情况有任何的矛盾。
另，我认为这里举出的两题是考察条件关系的典型，和“因果关系”没有必然联系。