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theoryland

Posts: 14
Joined: Tue Jul 20, 2010 9:34 am

4 questions.

what is the logical opposite of "could be true"?
what is the polar opposite of "could be true"?

Distinguish "could be true" from "not necessarily true"?

MOST IMPORTANTLY: How would you approach to a "could be true" question on the LSAT differ from a "not necessarily true" question?

EarlCat

Posts: 606
Joined: Mon Mar 12, 2007 4:04 pm

In LSAT land the opposite of "could be true" is "can't be true" or "must be false." This isn't a formal logic exam, so don't worry about labeling it.

Not necessarily true = could be false.

On a "could be true" question, cross out all the answers that can't be true. On a "not necessarily true" question, cross out all the answers that must be true.

JJDancer

Posts: 1564
Joined: Sun Jul 26, 2009 7:41 pm

The opposite of something that could be true is "not" could be true - meaning it can't be true.

Could be true means something could be the case, not necessarily true means it could NOT be the case (could be fals).

I have a little phrase for people on how to approach must be true questions. It's a little elementary/repetitive but here it is:

If a question asks MBT, and you can make an answer choice false, then it is not the correct answer.
If a question asks MBFalse, and you can make an answer choice true, then it is not the correct answer.

CBT questions: if you did the rules correctly, or if you understood the LR passage then ONLY one of the answer choices COULD BE TRUE, all others MUST be FALSE.

Imagine a MBT LG question.
Let's say answer choices A , B, and D are never true...they are must be false so they are obviously not the answer.
Answer choice C and E are COULD BE TRUE. But you need to find out which one MUST ALWAYS be true. So you try to make C false... like if C says "John must always teach math on Mondays" but you can have him teach it on tuesday and the rest of the game still works... then C is "made false" meaning it is NOT the must be true answer. Now try to make E false... probably if you change E/do its opposite/move it around then it won't work inside the game, meaning E has to stay as is, meaning it must be true.

Jeffort

Posts: 1888
Joined: Wed Jun 18, 2008 4:43 pm

For some reason many students never fully understand the importance and value of knowing logical opposites and extreme opposites in terms of how to use that knowledge to approach and quickly tear apart LG questions with as little work as possible.

Knowing the best strategy/approach for each different type of LG question is critical so you don't waste time running off in the wrong direction writing out a bunch of hypos on the page or whatever. The most efficient strategy varies by LG question type and is based on logical opposites.

When faced with a could be true question you know automatically that 4 of the 5 answer choices state things that Must be False according to the rules and deductions of the game. That means they violate a given rule or basic deduction. So you start by going through the AC's and quickly knock out those that violate one or more rules or deductions.

Most could be true questions are designed so that if you just apply the basic rules and basic set-up deductions you can usually eliminate at least 2, typically 3 AC's in a split second without wasting time writing out a single hypothetical to try things out. If any answer choice violates at least one rule or deduction you cross it off. Basic process of elimination. When you have it down to 2, if you cannot find a rule/deduction violation for either, THEN you make a hypo or two to flush it out.

Lot's of people unfortunately try the brute force 'plug and chug' method with CBT questions and make a hypo for each answer choice to see if it CBT. That is a very bad time wasting strategy since instead of making up to 5 hypos you could wipe out typically 3 and sometimes all 4 incorrect AC's without trying out a single hypo.

With a not necessarily true/could be false question you know that 4 of the AC's state things that must be true. First line of attack is to knock out the answer choices that state things that the rules and your set-up (assuming you made the proper deductions) already determine to be true. With these you get rewarded for having made the major deductions while creating your set-up and simply use that work to knock out AC's. Not necessarily true/could be false questions are far less common than the other types, probably in part because if it is a global question you can construct the crucial set-up deductions for the game from the 4 incorrect answer choices since they have to state things that must be true and you can then use that info to take down the rest of the questions with ease.

A giant yet very common strategic mistake with questions involving Must be True (whether it be a MBT question or a CBF question where POE involves knocking out the 4 incorrect MBT choices) is just making a hypo, plugging in what the AC says and seeing if you can make it all work. That strategy is fine to test if something could be true but does not determine if it MBT.

JesusChrist

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Joined: Wed Aug 25, 2010 12:44 am