#10 - Although the charter of Westside School states that

[Adam Tyson]

Actually mods, it would be good if you could address p.2-39 in the homework book, problem 1. "People with serious financial problems". Actually, I got all the drills in this section wrong, except for problem 3...and I didn't chart it right :/ (should I post this as a new post?)

Thanks for asking, Josue. Not sure if you ought to start a new thread on this question, but we're here, and it is about conditionality, so let's go for it.

This one can be approached somewhat mechanically, unlike our more challenging examples on this thread. "People with" is similar enough to our common indicator phrase "People who", which introduces a sufficient condition. So, that first premise becomes Serious Financial Problems -> Happy.

The argument later gives us something that looks almost like the contrapositive statement. That last sentence diagrams out as Can Be Happy -> Financial Problems Solved. Not that it's not exactly the contrapositive - this one doesn't say Serious Financial Problems, but rather Financial Problems.

The answer we're looking for IS the contrapositive, and that's answer E, as explained on the next two pages in the book.

What tripped you up on this one? Was it "people with" not being an exact match for "people who"?

Adam M. Tyson
PowerScore LSAT Instructor

[voodoochild]

I think you may still be losing the forest for the trees, voodoo. As Dave was saying above, sometimes you have to back away from the mechanical approach and ask yourself what the author actually means. In the case of either of the statements about trains and home, what is the author telling us? He's saying that the train is the sole option to get home. You can't walk home, can't ride a bike, can't drive a car, can't fly and Scotty can't beam you there. So, if you're home, how did you get there? The train - it's the only way. That's why those two variations you gave both lead to the same diagram: Home -> Train (if you are home, you must have taken the train).

Is the author saying that if you take the train, you must go home? Nope - he allows for the possibility that the train can be taken to get to work, to the theater, to the park or to the launch pad to meet up with Scotty. So Train -> Home isn't what he's saying.

Adam,
Thanks for your reply. I see your point that "the only way home is to take train" and "only way home is to take train" are basically the same. I get it.

However, now, when I looked at this statement below , I got confused.

"Only girls with blue eyes are beautiful" ---- I asked myself - If a girl possesses blue eyes, is she beautiful? I believe that the answer is "yes." Because "only" girls with blue eyes are beautiful..... Angelina Jolie is not beautiful. On the other hand, if a girl is beautiful, then will she possess blue eyes? Probably yes, because the definition of beautiful is defined as "only girls with blue eyes"....I am really lost. It seems to me that there is an if and only if condition (bidirectional conditionality).

I tried diagramming using Venn diagram, but gave up because I ended up overlapping the two sets - beautiful and blue eyes. Can you please guide me?

This problem is really giving me a hard time.....

[Steve Stein]

Hi Voodoo,

As you correctly pointed out, I think the issue is that you are trying to link beauty and blue eyes in both directions (as would be diagrammed with a )

If we can change the example slightly, I think the point will become clearer:

Only people who exercise become Olympic athletes.

In this example, which way does the arrow go? we can ask ourselves what information is valuable in this context. do we know anything about people who jog? Or, do we know something about people who make it to the Olympics:

Olympics --> exercise

...and, of course, we know something about people who don't exercise:

NOT exercise --> NOT Olympics

Now, back to your example:

Only women with blue eyes are beautiful:

Beautiful --> blue eyes
NO blue eyes --> NOT beautiful

I hope that's helpful--let me know whether it's clear--thanks!

~Steve

[voodoochild]

Hi Voodoo,

As you correctly pointed out, I think the issue is that you are trying to link beauty and blue eyes in both directions (as would be diagrammed with a )

If we can change the example slightly, I think the point will become clearer:

Only people who exercise become Olympic athletes.

In this example, which way does the arrow go? we can ask ourselves what information is valuable in this context. do we know anything about people who jog? Or, do we know something about people who make it to the Olympics:

Olympics --> exercise

...and, of course, we know something about people who don't exercise:

NOT exercise --> NOT Olympics

Now, back to your example:

Only women with blue eyes are beautiful:

Beautiful --> blue eyes
NO blue eyes --> NOT beautiful

I hope that's helpful--let me know whether it's clear--thanks!

~Steve

Thanks STeve. Now, I am able to understand this. however, if I modify your example :

the only people who eat mangoes are Mongolians.

How would we diagram this?

I believe Eat Mangoes -> Mongolians. Correct? My argument is that it shouldn't be.

If I eat mango, does it mean that I am Mongolian? haha No. I believe that it should be ...If Mongolian => Eat Mangoes. Correct? I am lost...


This is really confusing. We have two sentences with similar structure but different meanings. Why are the conditionals completely different? As per Adam's advice, I am not going to say that the distinction lies between "the only" and "only."

I am open to your thoughts.

[Steve Stein]

Thanks for your response. When you add "the," that does change the example.

Let's take a look at the subtle difference using the exercise example:

Only people who exercise make it to the Olympics.

As discussed, the necessary condition is exercise:

Olympics exercise

But what about this:

The only people who exercise make it to the Olympics.

And let's clarify this statement's implications:

The only people in the world who exercise are the ones who are going to the Olympics; everyone else just lies around.

This absurd statement isn't true in the real world, but how would that be diagrammed? Exercise Olympics

Tricky! That should finally makes sense, so thanks for a great discussion! We're going to lock the thread as the original topic got hijacked a bit by various questions unrelated to the original

~Steve

[lsat2014]

According to Page 248 of the PowerScore Logical Reasoning Bible:

Any "new" element in the conclusion will appear in the correct answer.

The new element in the conclusion of this question is "violation of its charter". This element does not appear in any of the premise.

Per the LR Bible, the correct answer must be choice E, which is the only choice with this element.

Yet, the correct answer is choice D. Choice D does not include this new element.

Can you please clarify? Is this LR step worded incorrectly or am I missing something?

Thank you

[Robert Carroll]

l,

You are correct that the premises don't mention the charter being violated, but they do mention a condition in the charter. The premises don't tell us that these conditions have been violated, but that's precisely what we need to find in the correct answer choice - something that, when added to the premises we already have, would add up to a violation. Because of that, we don't need the words "charter" or "violation," but the concept. Answer choice E is a tempting wrong answer choice because it is the only one that includes "charter" and "violated", but adding answer choice E to the stimulus doesn't give me a violation! It only tells me that we can't modify the charter in order to avoid a violation. The conclusion still talks about a violation existing when none has been proved.

Thus, we need to see what in the stimulus could lead to a violation of the charter. Since the charter requires the student body to include some students with special educational needs, if the student body lacked any such students, it would be in violation of the charter. Unfortunately, we only know that "no students with learning disabilities have yet enrolled." So the study body needs students with special needs, and it has no students with learning disabilities. If we could connect these two premises, the conclusion would follow. In other words, if "no students with learning disabilities" meant "no students with special needs," then this school would not have the students with special needs required by its charter.

In order for this conclusion to follow as required by a Justify question, we need this conditional to be true:

a student does not have a learning disability that student does not have special educational needs

The contrapositive of this is:

a student has special needs that student has a learning disability

Answer choice D can be paraphrased precisely this way.

Robert