#17 - People who have never been asked to do more than they

[Administrator]

Complete Question Explanation

Parallel Flaw—SN. The correct answer choice is (A)

Although many test takers had significant difficulty with this wordy stimulus, the author presents the following basic Mistaken Reversal:

• Conditional rule: not asked to do anything hard don't fulfill potential
  
  Alex: hasn't fulfilled potential not asked to do anything hard

The correct answer choice to this parallel flaw question will almost certainly contain a Mistaken Reversal as well.

Answer choice (A): This is the correct answer choice, presenting this Mistaken Reversal:

• Conditional rule: has a dog knows the value of companionship
  
  Alicia: knows the value of companionship has a dog

This flawed conclusion perfectly mirrors the one drawn in the stimulus, so this answer choice is a winner.

Answer choice (B): This cannot be the right answer choice, because rather than a Mistaken Reversal, here we see the following Mistaken Negation:

• Conditional Rule: Discovers something new has examined every solution
  
  Fran: Hasn't discovered something new hasn't examined every solution

Answer choice (C): To begin with, we should be wary of this answer choice because it deals with a topic related to that of the stimulus. Further, this cannot be the correct answer choice to this parallel flaw question, because the argumentation here is valid:

• Conditional rule: Not face enough challenge does not accomplish all possible
  
  Jill: Accomplishes all possible faces enough challenge

As the conclusion here is based on a valid contrapositive, this choice cannot be correct.

Answer choice (D): Like answer choices (B) and (C) above, this choice is based on valid reasoning and thus cannot be correct. The argument here is as follows:

A polygon is any straight-lined, closed-plane figure. The figure is a straight-lined, closed-plane figure, so it must be a polygon. This would be diagrammed with a double arrow, because the rule is basically this: something is a polygon if and only if it is a straight-lined, closed-plane figure.

Thus, the conclusion is valid, and this answer choice is incorrect.

Answer choice (E): At first glance, this may look like a Mistaken Reversal, but this choice changes both conditions at the end:

• Conditional rule: never lost something cant afford lax on security
  
  Jon: lax on security with things he can afford to lose never lost anything

While the reasoning here is clearly flawed, the flaw is not the classic Mistaken Reversal, so this answer choice is incorrect.

[a.lsat]

Hello PowerScore

I have just finished my first timed PT after reading al three bibles and the workbook, yet met some problem. Can you kindly help me with them?

==LR Section 3==

#17:
I get this question right, yet get some problem with the conditional reasoning in it.
Stimulus-Premises: ~Asked to do more ~Do all they can
Stimulus-Conclusion: (Alex) ~Do all he can ~Asked to do more
The premises/conclusion in the stimulus is invalid, as it is a mistaken reversal.
--
The correct answer (A):
(A)-Premises: Own a dog Know true value
(A)-Conclusion: (Alicia) Know true value Own a dog
The premises/conclusion in answer choice (A) is invalid either, as it is a mistaken reversal just like the stimulus.
--
However, I met problem with answer (B):
(B)-Premise: Discover something new Examine all possibilities
(B)-Conclusion: (Fran) ~Discover something new ~Examine all the possibilities
The premises/conclusion is invalid either and at the first glance, it seems not to be a good match with the reasoning in the stimulus.
Yet if we have the contrapositive of the "(B)-Premise," we will have the diagram "~Examine all possibilities ~Discover something new"
If we compare the contrapositive and "(B)-Conclusion," we will find that it is actually of the same flaw as the stimulus.

Why can't we choose answer (B) then?

[Adam Tyson]

You got it exactly right with your analysis of the conclusion and of both of those answer choices - job well done, nice diagramming and a clear understanding of what to do with conditional reasoning.

So, why is A a better answer than B? A is, as you pointed out, a Mistaken Reversal, just like the stimulus. B, however, is not a Mistaken Reversal, but a Mistaken Negation. While it is true that Mistaken Reversals and Mistaken Negations are the contrapositives of each other and therefore have the same logical meaning, in questions like this we want to be very picky about determining what the best answer is.

B might be the right answer if A wasn't around, but A is better because it is already in the form of a Mistaken Reversal. B requires us to take the contrapositive before we get where we wanted to go, and since B requires that extra step and A does not, A is the better answer.

Excellent job all around on this one! Just remember, we want to pick the best answer, not just a good answer (and sometimes the best answer isn't a good answer at all - it can be an awful answer and still be the best one as long as it's better than the other 4).

Good job, keep it up!

[a.lsat]

Hello Adam

Thanks for the explanation.
Got it! Thanks!

[Blueballoon5%]

For answer choice D, the answer key explains that, “A polygon is any straight-lined, closed-plane figure. The figure is a straight-lined, closed-plane figure, so it must be a polygon. This would be diagrammed with a double arrow, because the rule is: something is a polygon if and only if it is a straight-lined, closed-plane figure.” (quote taken directly from the answer key online)

My question: Why does the answer choice indicate a “if and only if”? Is it because it is a definition?

I feel like the premise would be: Polygon --> Any straight-lined, closed-plane figure
And the conclusion would be: A straight-lined, closed-plane figure --> Polygon.
This would make this choice a mistaken reversal, right?

[Shannon Parker]

hey there,

Arrow symbols are used to diagram necessary and sufficient conditions. A double arrow indicates an if-and-only-if relationship. In answer choice D the word any indicates that this relationship is both necessary and sufficient. "By definition a polygon is any closed plane figure bounded by straight lines." This means only closed plane figures bounded by straight lines are polygons, and that there are no closed plane figures bounded by straight lines that are not polygons. Thus, a double should be used when diagramming the relationship.

~Shannon

[Blueballoon5%]

Hi Shannon! Thanks for answering my question!

Would the rule you described look like this:
A is any B, means:
A <--> B

[Jonathan Evans]

Certainly, Blue. That particular syntax does indicate that something is a polygon if and only if it's a closed plane figure bounded by straight lines. I would warn you only not to try to create an exhaustive laundry list of rules for conditionals. There are limitless ways of introducing sufficient and necessary conditions. The sufficient condition indicators and necessary condition indicators are tools for you to use to identify the key components. Your job is still to think these relationships through. Is something sufficient to guarantee something else? Is something required for something else? Are the two sides equivalent to one another? These are the questions you need to be asking yourself when you encounter conditional language.