Q18 - All historians are able to spot trends

[clarafok]

hello,

so i can't figure out why the answer is A and not D!

this is how i saw it:

i thought the flaw was some kind of reversed logic right?
historians -> spot trends -> distinguish significant from insignificant
distinguish significant from insignificant -> historian

but how does A match this flaw? is this what A says?
poets -> expressions used for emotional impact -> figures of speech
figures of speech -> poets
????

i had to reread this a few times...am i on the right track?

thanks in advance!

[giladedelman]

You are on the right track. The original argument is reversed, just the way you diagrammed it. However, answer (A) actually looks like this:

figures of speech --> emotional impact --> used by poets
therefore, used by poets --> figures of speech

Notice that this answer choice didn't give the premises in the same order as the original argument. Don't be tricked by this kind of superficial change! We care only about the logical structure. It may be necessary to move premises around to make the parallelism evident.

Does that answer your question?

[LSAT-Chang]

You are on the right track. The original argument is reversed, just the way you diagrammed it. However, answer (A) actually looks like this:

figures of speech --> emotional impact --> used by poets
therefore, used by poets --> figures of speech

Notice that this answer choice didn't give the premises in the same order as the original argument. Don't be tricked by this kind of superficial change! We care only about the logical structure. It may be necessary to move premises around to make the parallelism evident.

Does that answer your question?

How would (D) look like?
I diagrammed it as follows:

Blues musician --> deep desire to communicate
Short story writers --> deep desire to communicate
Short story writers --> Blues musician

What is the mistake here?

[brandon.miller]

I think you have it diagrammed correctly (or at least that is how I would diagram it) but the key difference in my view is "could also have become blues musicians". The could in my eyes makes this a valid or at least plausible argument, whereas the prompt is flawed. If D would have said ALL short story writers are blues musicians than it would be similarly flawed.

Please correct if that is not true.

[timmydoeslsat]

I would say that definitely the could have been language is an issue since our conclusion is the stimulus is a very matter of fact "is a..."

The stimulus flaw is this:

A ---> B ---> C

Therefore, C--->A.


Answer D is:

Blues Musician ---> Deep Desire Communicate

Short Story Writer ---> Deep Desire Communicate

Even if this choice were to have said as its conclusion:

SSW ---> BM, we do not have a match in a flaw. The fact that it states could have been makes this choice even worse.

Answer A is clearly a match:

Fig of Speech ---> Express Emotional Impact ---> Expression used by Poets

Concludes Expression by Poets ---> Fig of Speech

[bernard.agrest]

Key: H - Historians. ST - Spot trends. D/S/I - Distinguish significant from insignificant.

H --> ST--> D/S/I
D/S/I --> H.

This is the logical form of A-B-C, therefore C-A. The fallacy is that its not C--A, but rather its A--C.

A) Disjointed BUT, EI--> UP. FS-->EI, link these together to get FS-->EI-->UP.
UP-->FS.

Just like in the stimulus you have an A--B--C--A structure.

B) Doesn't seem remotely close.
C) Wrong flaw, you cant conclude that if you fight a member of your species you arent a predator.
D) I fell for this A/C myself (which is why I'm writing up this explanation)... BM --> DDC. SSW --> DDC.
Conclusion: SSW--> BM.

All the argument says is that you need to have a DDC to become a BM. Here we learn that ALL SSW's have a DDC, therefore the argument is valid. It's not saying that they WILL become BM's, just that they could.

E)Just like B, it does not seem obviously similar to the flaw in the stimulus.

If my reasoning is off, please correct me.

[Emmeline Ndongue]

My two cents on (D)

Premise:
Blue->Deep
S->Deep
C: S [s->] Blue
#[s->]: some arrow

This is actually a valid inference! same logic is shown in Q21 of the same PT, except in that question it involves most statements.

The conclusion uses phrases "could have been", so it's reasonable to say that some [=1 or more] short-story tellers are Blue musicians.
If 2 things 100% (or >50% as in most claims) share the same necessary condition, then there has to be some overlap in between these two things, i.e. overlap between Blue musicians and short-story tellers.