sdcar请进，关于逻辑入门中no的疑惑

innerwarrior

Dear SDCAR,

As the "NO" part, I have one question:
For example: No one who is good at basketball can play tennis well.
I knew it equals to "One who is good at basketball cannot play tennis well."
My question is : does the example also equals to "One who is not good at basketball can play tennis well"
if yes, it's not the 逆否命题. or Lawyer's suggestion is wrong? thx

My question is from Lawyer's one tip:
No mathematical proposition can be proventrue by observation. It follows that it is impossible to know any mathematicalproposition to be true.
The conclusion follows logically if whichone of the following is assumed?
(A) Only propositions that can be proventrue can be known to be true
(B) Observation alone cannot be used to provethe truth of any proposition.
(C) If a proposition can be proven true byobservation then it can be known to be true.
(D) Knowing a proposition to be true isimpossible only if it cannot be proved true by observation
(E) Knowing a proposition to be truerequires proving it true by observation
该题：推理：因为mathematical proposition NO PROVE BY OBSERVATION，所以mathematical propositionIMPOSSIBLE KNOW TO BE TRUE(概念跳跃为PROVE By observation，KNOW)。推理方向从NO PROVEBY OBSERVATION到 IMPOSSIBLEKNOW。（注意：这里没有充分必要关系，即不能将原文写成NO PROVE BY OBSERVQATION---〉IMPOSSIBLE KNOW。）

A：意思为proposition KNOWN TO BE TRUE--->ROPOSITION CAN BE PROVE。该选项很容易混。因为推理方向对：逆否命题从NO PROVE 到IMPOSSIBLE KNOW。且概念也很象，包含和被包含的概念（proposition包含mathematical proposition），概念比原文大在这类题中是允许的。但它错在没有说明PROVE的方式，原文有说明PROVE的方式为BY OBSERVATION。这也是和E选项的唯一区别。所以A选项加BYOBSERVATION便为答案。

B：没有KNOW的概念。错

C：CAN BE PROVE BY OBSERVATION---〉 KNOWN TO BE TRUE。逆否命题为IMPOSSIBLE KNOWN TO BE TRUE--->CANNOT BE PROVE BY OBSERVATION。和原文推理相反。错

D：IMPOSSIBLE KNOWN TO BE TRUE--->CANNOT BE PROVE BY OBSERVATION.和原文推理相反。错。

E：KNOWN TO BE TRUE--->CAN BE PROVE BY OBSERVATION（注意REQUIRE带必要条件）。逆否命题为：CANNOT BE PROVE BYOBSERVATION---〉IMPOSSIBLEKNOWN TO BE TRUE。和原文推理方向一致。正确答案。

注明：该题较特殊。除了两个推理相反的选项。还有一个概念相似的混淆项。

innerwarrior

还有一题，关于only if的

33.    Advertisement: Today's customers expect high quality.
Every advance in the quality of manufactured products
raises customer expectations. The company that is
satisfied with the current quality of its products will
soon find that its customers are not. At MegaCorp,
meeting or exceeding customer expectations is
our goal.
Which of the following must be true on the basis of the
statements in the advertisement above?
(A)    MegaCorp's competitors will succeed in
attracting customers only if those competitors
adopt MegaCorp's goal as their own.
(B)    A company that does not correctly anticipate the
expectations of its customers is certain to fail in
advancing the quality of its products.

0 MegaCorp's goal is possible to meet only if
continuing advances in product quality are
possible.
(D)    If a company becomes satisfied with the quality
of its products, then the quality of its products
is sure to decline.
(E)    MegaCorp's customers are currently satisfied
with the quality of its products.

根据原文的逻辑链：
if advance in the quality of manufactured , then raises customer expectations. (every=if)
MegaCorp's goal is to meet/extend customer expectations=>if meet/extend customer expectations, then meet MegaCorp's goal

所以原文逻辑链是advance in the quality of manufactured->raises customer expectations.->meet MegaCorp's goal

而选项C是MegaCorp's goal is possible to meet only if
continuing advances in product quality are
possible.

only if=then, =》if MegaCorp's goal is possible to meet then continuing advances in product quality are
possible.

这个。。。和原文的逻辑链相反，怎么会是正确答案呢？
希望斑斑指点～谢谢～

sdcar2010

Dear SDCAR,

As the "NO" part, I have one question:
For example: No one who is good at basketball can play tennis well.
I knew it equals to "One who is good at basketball cannot play tennis well."
My question is : does the example also equals to "One who is not good at basketball can play tennis well"

-- by 会员 innerwarrior

Correct: One who can play tennis well is not good at basketball.
Wrong: One who is not good at basketball can play tennis well.

Which part of lawyer's explanation you do not understand or have questions?

P.S. I am not a 版主 here. Only a member.

sdcar2010

For the Advertisement question:

This is a must-be-true question, one of the easiest for CR because the answer HAS been stated in the stimulus. You job is just to find it!

C is totally true because it is the necessary assumption for the argument.

Necessary assumption question is a type of must-be-true question. In this case,  which is a must be true question, the must-be-true part is the assumption made by the author - continuing advances in product quality are possible  - to reach his main conclusion: The company can meet its goal.

根据原文的逻辑链：
if advance in the quality of manufactured , then raises customer expectations. (every=if)
MegaCorp's goal is to meet/extend customer expectations=>if meet/extend customer expectations, then meet MegaCorp's goal

Your second analysis is wrong. This is a simple statement of "MegaCorp's goal = meet/extend customer expectations." If anything, this is an if and only if statement, not if-then statement ONLY.

innerwarrior

Dear SDCAR,

As the "NO" part, I have one question:
For example: No one who is good at basketball can play tennis well.
I knew it equals to "One who is good at basketball cannot play tennis well."
My question is : does the example also equals to "One who is not good at basketball can play tennis well"

-- by 会员 innerwarrior

Correct: One who can play tennis well is not good at basketball.
Wrong: One who is not good at basketball can play tennis well.

Which part of lawyer's explanation you do not understand or have questions?

P.S. I am not a 版主 here. Only a member.

-- by 会员 sdcar2010 (2011/10/19 22:51:18)

听你这么解释木有问题了，哈哈，谢谢sdcar～

innerwarrior

For the Advertisement question:

This is a must-be-true question, one of the easiest for CR because the answer HAS been stated in the stimulus. You job is just to find it!

C is totally true because it is the necessary assumption for the argument.

Necessary assumption question is a type of must-be-true question. In this case,  which is a must be true question, the must-be-true part is the assumption made by the author - continuing advances in product quality are possible  - to reach his main conclusion: The company can meet its goal.

根据原文的逻辑链：
if advance in the quality of manufactured , then raises customer expectations. (every=if)
MegaCorp's goal is to meet/extend customer expectations=>if meet/extend customer expectations, then meet MegaCorp's goal

Your second analysis is wrong. This is a simple statement of "MegaCorp's goal = meet/extend customer expectations." If anything, this is an if and only if statement, not if-then statement ONLY.

-- by 会员 sdcar2010 (2011/10/19 23:03:28)

彻底明白了！！！谢谢大神在偶考前送来的及时雨：）