Q20 - Selena claims to have

[joshgra92]

I do not understand why B is the correct answer; it seems ridiculous to me. Can someone please help me to understand?

[ManhattanPrepLSAT1]

Hi Josh, thanks for bringing this one to the LSAT Forums!

Lets start with the argument core.

Evidence: Selena claims to have psychic powers.

Conclusion: So if we find out that Selena's claim is true, then we'll thereby determine whether it's possible to have psychic powers.

On this Sufficient Assumption question we want an answer that ensures the conclusion follows. Suppose we assume that (B) is true; that if it is possible to have psychic powers, then Selena has them. Now ask yourself, would that justify the conclusion that finding out whether Selena's claim were true would indicate whether it's possible to have psychic powers? It would indeed, because if it's possible to have psychic powers then Selena has them, and finding out about them would tell us whether it's possible to have psychic powers.

The problem with the argument rests in the possibility that Selena's claim is false, and all the while it were possible to have psychic powers anyway. We need a link between what's true for her and what's true generally. Answer choice (B) provides that link.

Incorrect Answers
(A) doesn't connect the generality back to Selena, nor does it ensure one way or the other whether it is possible to have psychic powers.
(C) misses the fact that the conclusion is conditional. We're concerned with whether finding out that Selena has psychic powers tells us whether it's possible to have psychic powers. We're not concerned with how we find out whether Selena has psychic powers, but what finding that out would mean.
(D) hurts the conclusion by suggesting one circumstance that where we wouldn't know whether it were possible to have psychic powers.
(E) reverses the logic of the conditional statement in the argument's conclusion.

#officialexplanation

[levym93]

"The problem with the argument rests in the possibility that Selena's claim is false, and all the while it were possible to have psychic powers anyway. We need a link between what's true for her and what's true generally. Answer choice (B) provides that link."

Hi Matt, thanks for your explanation. I wanted to ask about the above part of your explanation.

When I first read this stimulus, I was confused by the question and the answer choices. I felt that the second sentence "So if... psychic powers" meant that if true we know its possible and if not true we know its not possible.

I deduced that from the fact that it used whether two times. I took "if we find out whether Selena's claim is true" to mean whether it is true or false. And I took "determine whether it is possible" to link up to the previous part, meaning If true-then possible, if not true then not possible.

Where am I going wrong here?

[ManhattanPrepLSAT1]

Hey levym93, great question.

I think the issue is here:

And I took "determine whether it is possible" to link up to the previous part, meaning If true-then possible, if not true then not possible.

The issue is that Selena having psychic powers is not a very good match for whether it is possible to have psychic powers. The latter possessing a much higher chance of occurring. If it is possible to have psychic powers, that does not mean that Selena has them. However, if Selena has psychic powers, then we would know it is possible to have them.

Since they're not a match, we'll need to bridge the gap and I believe that is why the following popped up on your radar as something that needs to be clarified.

"The problem with the argument rests in the possibility that Selena's claim is false, and all the while it were possible to have psychic powers anyway. We need a link between what's true for her and what's true generally. Answer choice (B) provides that link."

Hi Matt, thanks for your explanation. I wanted to ask about the above part of your explanation.

My point above was to close the gap in the argument wherein Selena does not have psychic powers, even though it is possible that someone else might have them. Under that circumstance, finding out whether Selena has psychic powers would be of no assistance to establishing whether it is possible to have psychic powers.

Hope that helps!

[fanshuhaodg]

Just to add on some extra explanations since it took me a while to figure it out despite reading the helpful responses above.

What I missed in the conclusion earlier is that it is in fact two-folded:
"If we find out whether Selena's claim is true, we can determine whether it is possible to have psychic powers" essentially breaks down into two parts:
1) If we find out the claim is true, we can determine it is possible. (which is quite common sense, needing no additional assumption)
2) If we find out that the claim is not true, we can also determine that it is not possible. (this second part is where we need to assume in order to make it valid)

As a result, only choice b) fills up the gap in part 2). If you negate choice b), it says, "If Selena does not have them (i.e., claim not being true), it is not possible to have psychic powers."

Hope that helps if anyone has similar questions as I did.

[AyakiK696]

Was a little confused by the contradicting replies above (although I may have just misinterpreted them). So, just to clarify, is the argument actually stating that if we find out whether Selena's claim is true or false, we will determine whether it is possible to have psychic powers, i.e. that whether or not it is possible to have those powers hinges on whether Selena herself has them? Meaning that if she DOESN'T, then it means that it's not possible to have them?

I interpreted it more as "If we find out that her claim is true, THEN we can determine if it's possible to have psychic powers." This interpretation leaves room for the possibility that she doesn't have psychic powers BUT someone else may. I feel like this is more logical, rather than Selena being the ultimate decider or whether or not this ability exists.

I can see how if the first interpretation had been correct, then B makes a lot of sense as an answer, especially given the contrapositive (if Selena DOESN'T have powers, it's not possible to have them).

However, I can see how B also fits with the second interpretation--in that it proves that if it IS possible at all, THEN selena has that ability--although the contrapositive wouldn't then work.

I can pretty much rule out all of the other answer choices, but I really don't see how B makes sense... Would really appreciate any help with this! Thank you!

[ohthatpatrick]

The contrapositive of (B) reads like this:
If Selena doesn't have psychic powers, then it is impossible to have psychic powers.

The conclusion is saying, "if we find out whether Selena has psychic powers, we'll know whether it's possible to have psychic powers".

This is a "damned if you do, damned if you don't" type of Sufficient Assumption, meaning that it creates a situation where whether X is true or X is false, we get to the conclusion either way.

If we find out Selena DOES have psychic powers, then clearly we've determined whether it's possible to have psychic powers (you only need one example of it happening to determine that it's possible).

If we find out Selena DOES NOT have psychic powers, then the rule in (B) tells us that "it's impossible to have psychic powers", so we will have clearly determined whether it's possible to have psychic powers.

tl;dr version:
if she has them, we've determined it's possible to have them.
if she doesn't have them (+ the rule in B), we've determined it's impossible to have them.

So the conclusion is right! Finding out whether Selena has psychic powers will allow us to determine whether it's possible to have them.

If you want another example of a "damned if you do, damned if you don't" sufficient assumption, try this one:
https://www.manhattanprep.com/lsat/foru ... 13358.html

[Kcb77]

Hey guys,

The explanations to this question have been great, but I think a critical part has been left out and adding it in can bring about a much clearer view of what is going on in this question. But Please, I'd like some feed back from contributors on the position I take.

Okay, The argument begins by giving us the premise that Selena claims to have psychic powers, but the conclusion is where we need to focus to get this question right, It then concludes that if we can determine WHETHER Selena's claim is true, Then we can determine WHETHER it is possible to have psychic powers. Notice that I put both uses of the word whether in all caps and bolded them. Understanding this question, in my view, hinges on understanding what exactly the word whether does. When a speaker or author uses the word whether, they are essentially setting up two "worlds"--one in which something is true and one in which that thing is false.

In this question, the conclusion states that, "if we can determine WHETHER Selena's claim is true", e.g. Selena has psychic powers...:this translates to the two "worlds" below:


Selena has psychic powers

Selena DOES NOT have psychic powers


...then we can determine WHETHER it is possible to have psychic powers: this translates to the two "worlds" below:


It is possible to have psychic powers

It is NOT possible to have psychic powers


Now, If Selena HAS psychic powers, then it is indeed possible to have psychic powers (Selena having psychic powers but it being impossible to have psychic powers CANNOT happen together). Therefore,

Selena has psychic powers ----------> possible to have psychic powers.


At this point, many LSAT preppers understand whats going on. However, it seems to require some invisible premise even before we add in a sufficient assumption. How do we COMPLETELY FIX this argument?

Again, it, in my view, hinges on understanding what using the word WHETHER does (and remember its used twice).

We've established that "WHETHER" implies both instances of something is true and of it being false, and as it pertains to this question: the sufficient condition given in the conclusion... "if we can determine WHETHER Selena has psychic powers", is translated


Selena has psychic powers

Selena DOES NOT have psychic powers

(But PLEASE understand that BOTH statements are implied by the sufficient condition)


And the necessary condition given in the conclusion..."then we can determine WHETHER it is possible to have psychic powers", is translated

It is possible to have psychic powers

It is NOT possible to have psychic powers

(But PLEASE understand that BOTH statements are implied by the necessary condition)


Okay, remember that if Selena HAS psychic powers then it is possible to have psychic powers. Now, in order to FIX the argument by ensuring the conclusion, we need to connect the part of the sufficient condition that we haven't yet addressed and the part of the necessary condition that we haven't addressed, e.g.,

Selena DOES NOT have psychic powers ---------------> It is NOT possible to have psychic powers

(The test writers chose to proffer the contrapositive of this statement in the correct answer choice.

"If it IS possible to have psychic powers, then Selena has them".)


Essentially, the question requires us to assume a biconditional relationship between Selena having psychic powers, and it being possible to have psychic powers.


TAKEAWAYS
WHETHER DOES EQUAL IF, AND IF NOT (simultaneously)

WHETHER DOES NOT EQUAL THAT

WHETHER DOES NOT EQUAL IF



Please let me know WHETHER this hits the mark.

--Thanks