#18 - All historians are able to spot trends. But anyone

[Administrator]

Complete Question Explanation

Parallel Flaw. The correct answer choice is (A)

This is a classic Mistaken Reversal of conditional reasoning. The stimulus can be diagrammed as follows:

• Prem: Historian Spot trends Can distinguish sig.
  
  Conc: Can distinguish sig. Historian (Mistaken Reversal)

Answer choice (A): This is the correct answer choice. It contains a Mistaken Reversal (the order of the premises is unimportant in Parallel Reasoning):

• Prem: Fig. of speech Emot. Impact Used by poets
  
  Conc: Used by poets Fig. of speech (Mistaken Reversal)

Answer choice (B): This answer does not contain a Mistaken Reversal (it is close to a repetition if you consider autocrats to be not elected legislature).

Answer choice (C): The premise relationship in this answer is different from the one in the stimulus:

Dec 02_LR1_#18 powerscore_lsat_course_M12_L8_explanations_Par Flaw_#7_diagram_1.png

• (note how the arrows go in opposite directions)

Answer choice (D): This is actually valid reasoning, although it appears to be invalid at first:

Dec 02_LR1_#18 powerscore_lsat_course_M12_L8_explanations_Par Flaw_#7_diagram_2.png

The arrows are pointing in opposite directions so people sometimes presume this to mean that no inference can be made. However, the reason that this is argument is valid has to do with the soft language of the conclusion. The conclusion simply states that short story writers can be blues musicians. For this to be true, short story writers merely need to possess the necessary condition(s) of a blues musician, so here they must have a deep desire to communicate. Since they have the necessary condition, it is possible that they can be blues musicians (it has not yet been ruled out), and the conclusion is correct. To conclude anything stronger than “can” would be incorrect, but the possibility still exists so “can” is acceptable.

Of course, the premise relationship still does not match the stimulus, so this answer choice does not parallel the Mistaken Reversal presented there.

Answer choice (E): This answer choice introduces a new term/idea in the conclusion, as it tries to relate the fact that a country’s past is never the product of free choice with the notion of people being free. These are different ideas so this does not parallel the stimulus.

[Blueballoon5%]

Answer choice (C): The premise relationship in this answer is different from the one in the stimulus:

Dec 02_LR1_#18 powerscore_lsat_course_M12_L8_explanations_Par Flaw_#7_diagram_1.png

• (note how the arrows go in opposite directions)

Hello! I am a bit confused with the way the arrows are positioned here. Why is the arrow pointing outward in this manner? I've never seen a conditional statement before in the lesson of an arrow that points westward.

_________

Answer choice (D): This is actually valid reasoning, although it appears to be invalid at first:

Dec 02_LR1_#18 powerscore_lsat_course_M12_L8_explanations_Par Flaw_#7_diagram_2.png

The arrows are pointing in opposite directions so people sometimes presume this to mean that no inference can be made. However, the reason that this is argument is valid has to do with the soft language of the conclusion. The conclusion simply states that short story writers can be blues musicians. For this to be true, short story writers merely need to possess the necessary condition(s) of a blues musician, so here they must have a deep desire to communicate. Since they have the necessary condition, it is possible that they can be blues musicians (it has not yet been ruled out), and the conclusion is correct. To conclude anything stronger than “can” would be incorrect, but the possibility still exists so “can” is acceptable.

Of course, the premise relationship still does not match the stimulus, so this answer choice does not parallel the Mistaken Reversal presented there.

I have the same question here for answer choice D.

Moreover, I think I am the most confused with translating this sentence, "No one without a deep desire to communicate can be a blues musician." I am not sure how to begin to translate this to a conditional form. The phrase "no one" and "without" throw me off.

I hope you can help! Thank you!

[Adam Tyson]

Hey there blueballoon, don't be too confused by that first diagram, as it still means the same thing as any conditional arrow - the arrow points from the sufficient to the necessary. It's just a little difficult to show a single sufficient condition with multiple necessary conditions using the tools available in this forum. We could have done it like this, too:

Horns & Antlers Intraspecies Combat & Predator

Clearly not what happened in the stimulus, right?

For D, same thing - it was just a matter of convenience because of the difficulty of using some tools here. It could have been like this:

Blues Musician

or      Deep Desire to Communicate

Short Story Writer

As to the translation of "no one without" something, try thinking of it more holisitically for a moment. What does it mean? Can you say it using "if...then" and retain that meaning? It's "if you don't have that desire, you cannot be a blues musician" or the contrapositive, "if you are a blues musician, you have that deep desire." Play around with paraphrasing that sentence to see what makes sense and what does not. It wouldn't make sense, or capture the author's meaning, if it were "if you have a deep desire to communicate, then you are a blues musician," right?

There are more formal, technical approaches to doing that translation, and you can find some discussion of them in the LR Bible if you happen to have that excellent book, but I tend to go for this more holistic approach when faced with those confusing combinations.