Q10 - Lawyer: This witness acknowledges

[ohthatpatrick]

Question Type:
Sufficient Assumption

Stimulus Breakdown:
Conclusion: Witness's testimony should be excluded.
Evidence: The witness recognizes the assailant, but not the victim (and the victim is famous)

Answer Anticipation:
Since the conclusion is trying to prove "testimony should be excluded" but we were never given a rule that lets us conclude that, we KNOW the correct answer will have the form "If [something we know gets triggered by the evidence], then the testimony should be excluded." It's hard to prephrase that first half, but it could be something like "If you recognized the non-famous attacker but didn't recognize the famous victim, your testimony should be excluded".

Correct Answer:
D

Answer Choice Analysis:
(A) 2nd half works, but the 1st half is NOT triggered, since the witness only recognized one of the two parties.

(B) Worthless - doesn't give a "should be excluded" rule.

(C) Same as B. Worthless unless it's a "should be excluded" rule.

(D) Yes! Like many correct Sufficient Assumption answers, it's written in contrapositive form. This says "include testimony --requires--> recognizing both parties". So when we contrapose, we get "if you didn't recognize both parties, your testimony should be excluded". We can trigger that rule with what we know about the witness and derive the conclusion.

(E) Worthless - doesn't give a "should be excluded" rule.

Takeaway/Pattern: Understanding how a New Guy in the Conclusion (an undefined term/idea) will HAVE to be defined in the correct answer would allow us to only need to really read A and D. In classic LSAT tradition, the correct answer was written in the contrapositive of its applicable form.

#officialexplanation

[opulence2001]

Hello,

Could someone please explain why D is the correct answer over E?

Thanks in advance!

[bermudask8er7]

opulence2001,

The lawyer argues for exclusion of the testimony.

D states the following:
testimony to be included -> witness claims to recognize both involved parties
Therefore we get the contra-positive:
witness does not claim to recognize both involved parties -> testimony should not to be included

The premise states that the witness did not claim to recognize the famous client; therefore the witness did not claim to recognize both involved parties. As a result, if D is assumed to be true, it established the conclusion that the testimony should be excluded.

Whether it is unlikely for people to recognize the famous client, as E states, is irrelevant. Even if E is assumed to be true, it does not fulfill the gap to fully establish the argument.

Hope that this helps.
bermudask8er7

[bbirdwell]

pretty good explanation, bermuda! nice work with the conditional logic.

The argument is like this:
Witness recognized assailant and did not recognize famous client. Therefore, witness should be excluded.

There's quite a gap between that little piece of evidence and the conclusion. We need an answer choice that will close that gap and make the argument sound.

(E) doesn't do that. So what if it's unlikely that someone would fail to recognize the client? This witness didn't. The trap here is that you begin to believe, "Oh! That seems to say that the client is lying, and that would be a great reason to exclude his testimony!"

This is the kind of thinking that leads to trouble on the LSAT because it's a kind of interpretation that's full of assumptions itself. We need to avoid interpreting, and instead, analyze. (D) does nothing more than put the witness into the "unlikely" category, which doesn't mean much at all.

(D) connects the logic of the argument clearly, and validates the conclusion by doing so. IF it's true that we should only include the testimony when a witness recognizes both parties, then clearly we cannot accept this witness's testimony, because he only recognized one party!

See what I mean?

[opulence2001]

Thanks so much to you both!

Both explanations are very clear and make sense. I definitely overestimated the value of being in the unlikely category (my own faulty assumption), and I see now how D clearly connects to the argument.

Much appreciated.

[cimani.w]

How are A and D different except thay they are just written as opposites of each other? They both still say the same thing? And why are you doint thecontrapositive of choice D? I thought that if you were testing what the assumption is you just negate your contenders? Also when you negate both A and D they both still have the conclusion still standing as a firm one. When you negate them, the conclusion does not fall apart.

[farhadshekib]

How are A and D different except thay they are just written as opposites of each other? They both still say the same thing? And why are you doint thecontrapositive of choice D? I thought that if you were testing what the assumption is you just negate your contenders? Also when you negate both A and D they both still have the conclusion still standing as a firm one. When you negate them, the conclusion does not fall apart.

Let's break it down:

P1 - Witness saw famous person assaulted at restaurant.
P2 - Witness claims to recognize assailant, but not famous person.
C: Witness testimony should be excluded.

(A) can be diagrammed like this:

Witness recognize both parties in assault --> Witness testimony should be included.

Contrapositive: Testimony excluded --> witness did not recognize both parties in assault.

But (A) doesn't tell us much. The sufficient condition only deals with what happens when the witness recognizes both parties to an assault.

However, we know that our witness only recognized one party in this case.

Moreover, the contrapositive, logically, deals with what happens when the testimony is exlcuded - and not with why the testimony should be excluded.

(D) can be diagrammed like this:

Testimony of witness included --> witness claims to recognize both parties in the assault.

Contrapositive: If the witness does not claim to recognize both parties in an assualt, the testimony should be excluded.


It appears as if the contrapositive, here, validates the conclusion

Moreover, it seems that (A) is a reversal of the correct answer, (D), so I see why it can be tempting.

As for your second question: the negation technique, which works only with necessary assumptions, is not applicable here, since this question is asking for a sufficient assumption.

[jennifer]

Is this a sufficent assumption?

Can you break down the logic and please explain how A and D differ and why D is correct. Thank you

[bbirdwell]

Yes, the question type is "sufficient assumption."

The difference between A and D is that A says "If," which introduces a sufficient condition (the left side of a statement), and D says "only if," which introduces a necessary condition (the right side).

So, A and D are reversals of one another.

The argument is like this:
1. witness present when famous person assaulted
2. witness recognizes assailant, does not recognize famous person

Conclusion: witness should be excluded.

(A) says: recognize both --> included.

This does not help our argument. We need to conclude that the testimony should be excluded, not included, as this choice reflects.

(D) is much different: testimony included --> recognize both.
The contrapositive of this statement is exactly what we need:
if both are NOT recognized --> testimony NOT included.

This is a match for the logical structure of the original argument!

[Joymarie.virga]

I am still not completely clear on the one. The repeated reference to the famous client led me to choose E. I thought that the lawyer was saying that it is unlikely that anyone would not recognize the famous client but recognize the assailant and therefore the witness must be unreliable. Can someone please help?

[timmydoeslsat]

I am still not completely clear on the one. The repeated reference to the famous client led me to choose E. I thought that the lawyer was saying that it is unlikely that anyone would not recognize the famous client but recognize the assailant and therefore the witness must be unreliable. Can someone please help?

Our question stem wants us to select an answer choice that will prove our argument true. We want to guarantee the truth of the conclusion. Our conclusion is that the testimony should be excluded. In our evidence, we have no mention of exclusion of evidence.

Our evidence does provide us information that the witness recognized one member involved in the assault and not the other, that being the famous personality.

So answer choice E would tell us that the witness is not like most people, but it fails to justify that the testimony should be excluded.

Answer choice D gives us the classic construct of arriving at an idea. We want to prove "should exclude."

This answer choice gives us a requirement of inclusion for testimony. Failing to meet this requirement, which the stimulus does, will guarantee to not include.