SDCAR2010【逻辑入门】（十四）Formal Logic (2)

sdcar2010

Unless

The word unless can also create an if-then relationship. But it can bethe most confusing and counterintuitive “logic” word. Consider this example:
Your CR score will not be high unless you study formal logic.

There are two ways to translate this statement into if-then clauses:
1) If your CR score is high, then you have studied formal logic.
2) If you did not study formal logic, then your CR score will not behigh.

The second method is the foolproof way, which replaces unless with if not. The preferred way is the firstmethod, which negate the clause before unless andcap it with if,and replace unless with then. Basically the clause after unless is the necessary condition which musthappen for the negated form of the other clause. Back to the example we havehere, “study formal logic” is a necessary step for one to get high score in CR.Without “studying formal logic”, one would not be able to score a high mark inCR. But “studying formal logic” alone might not be sufficient to help you scorehigh in CR.

When the unless-clause comes at the beginning of the sentence, everythingbetween the word unless andthe comma is the unless-clause.


Either

The word either can also create an if-then relationship. Consider thisexample:
Either Peking University or Tshinghua University is on the list of mydream schools.

Given this rule, if PKU is not on my list, then THU is on my list because oneof them must be. Further, the rule does not exclude the possibility that bothschools are on my list. Therefore, the correct way to say the same thing usingif-then clauses is:
If PKU is NOT on my list, then THU is.
Notice the word NOT is added to the if-clause, not the then-clause.Otherwise, we would make the mistaken assumption that both schools cannot be onthe list together, which is not necessarily true—at least on the GMAT or LSAT.


Hiddenif-then statements

Many if-then statements on the test are hidden because they do not use if or then. Instead, they use words like all, any, when, must and so on. Consider thisexample:
All Chinese students are diligent.
Translation: If you are a Chinese student, then you are diligent. (Itruly hope so!!)

The trick here is that all means if.

There are also words that mean then. Here is another example:
Reading SDCAR’s posts on CR requires good understanding of English.
Translation: If you can read SDCAR’s posts on CR, then you have goodunderstanding of English. (Pat yourself on the back, please!!)

Here are more words you can use to find hidden if-then statements:

If: All, always, any, each, every, inorder to, invariably, no, none, things that, those who, to, when.

Then: Depends on, essential, must,necessary, needs, only, only if, only when, prerequisite, requires.

Unless (ifnot): Except, until, without.


No
When you see no atthe beginning of a sentence, change no to if and negate the other clause, which isyour then clause. Example:
No one who has a cold should go outside. (No X is Y.)
Translation: If you have a cold, then you should NOT go outside. (If X,then NOT Y.)


Most,some, and not all
Most means more than half. Most could be all.
Some means at least one. Some = Many. Some could be most,could be all.
Not all means some did not. Not all could be none.

SDCAR2010【逻辑入门】（十三）Formal Logic (1)

SDCAR2010【逻辑入门】（十五）More on Negation

米样

咦，抢到沙发啦，(*^__^*) 嘻嘻……

srosalita

板凳～～ 继续学习！！ 看了LZ的assumption那篇文章，，，很迷茫。。。觉得都没看懂。。 只能强迫自己继续学。。。NO SHORTCUT...

kzhang85

太有用了。。多谢多谢

VincentShu

I felt if we take mathematics‘s logic into CR, CR will be easier.

jasminerocks

还会继续更新吗，持续关注

qiuhua01234567

坐等更新啊

bitieming

Why either or can not rule out the possibility of both?

mia113

Thanks a lot `sdcar2010
But I'm confused why you classified about the one question related to the "no"
In an attempt to reduce the crime rate, the governor is getting tough on criminals and making prison conditions harsher.Part of this effort has been to deny inmates the access they formerly had to college-level courses.However, this action is clearly counter to the governor’s ultimate goal, since after being released form prison, inmates who had taken such courses committed far fewer crimes overall than other inmates.
Which of the following is an assumption on which the argument depends?
A.Not being able to take college-level courses while in prison is unlikely to deter anyone from a crime that he or she might otherwise have committed.
B.Former inmates are no more likely to commit crimes than are members of the general population.
C.The group of inmates who chose to take college-level courses were not already less likely than other inmates to commit crimes after being released.
D.Taking high school level courses in prison has less effect on an inmate’s subsequent behavior than taking college-level courses does.
E.The governor’s ultimate goal actually is to gain popularity by convincing people that something effective is being done about crime.
Correct answer is:C
However for the choice A:
Not being able to take college-level courses while in prison (X) is unlikely to deter anyone from a crime (Y) that he or she might otherwise have committed.
Not X is unlikely Y
-->If x, is Y
that means being able to take college-level courses while in prison  is likely to deter anyone from a crime -->This sentence is just the gap needed
I'm totally faint....please help me...thanks a lot``

sdcar2010

NO does not equal NOT.