Q23 - Principle: It is healthy

[noah]

I feel like a geek hero, swooping in to save the day! However, I think Timmy has a pretty good explanation. Here's my take on it:

We need to see a flaw in the application of a principle.

The principle has a nice juicy "only if" in there, so I'd pay attention to the necessary and sufficient.

It boils down to healthy --> ~ detracting from soc. dev.

Pretty straightforward so far. The contrapositive is easy: detracting from soc. dev. --> ~ healthy.

The application concludes that Megan's reading is not healthy. So, we should learn that it detracts from her social development. Instead, we learn that it reduces the amount of time she spends with others. Is that detracting from her social development? Hmmm, smells like a gap to me!

(D) points out this very gap - the argument assumes that lost interaction time detracts from social development.

As for the other answers:

(A) splits hairs between a universal claim and a generalization. The principle gives us a universal claim - it's a conditional statement, it should be always true!

(B) brings in other considerations. We need to stick to how the application messes up the principle. In essence, (B) is a premise de-booster.

(C) is tempting, as some LSAT arguments do a naughty switch like this (e.g. is something that is not bad good?). However, the application never actually refers to something being "unhealthy"--we are simply told something is "not healthy." Thus, the application bypasses this issue.

(E) is always tempting - it sounds so LSAT-like! However, there's no switching around here. In this case, that would sound like this: What Tom is doing doesn't detract from his social development, thus it is a healthy intellectual activity.

That clear it up?


#officialexplanation

[supermissykim]

I can see why D is correct-- the application does make a logical jump when it says that a reduction in people interaction is the same as detracting from social development.

But, what is C saying? Its wording was so weird that I ended up picking it because I didn't understand it well.

[timmydoeslsat]

The stimulus is:

Healthy to engage in activity that promotes intell.dev. ---> ~Activity detracts from social dev.

Contrapositive:

Activity detracts from social dev. ---> ~Healthy to engage in activity that promotes intell. dev.

The application is:

Reduces amount of time she spends interacting with people ---> ~Healthy

Obviously, the application is assuming that reducing such time interacting with people will detract from social dev., which is answer choice D.


(C) In my opinion could never be right because the contrapositive and the original form of the principle cover claims of both healthy and unhealthy.

We will not be able to conclude what is healthy, but rather what is ~healthy. However, although we cannot conclude what is healthy, it is still a claim about healthy, as it gives us a necessary condition of what is healthy. I would argue that is still a claim nonetheless of course.

[jennifer]

Can a Manhattan LSAT employee please explain how they would eliminate each wrong answer choice, I had a problem with this problem and still dont have a handle on it.

[jreeve12]

Here's the source of my confusion with the given explanations for why answer choice (C) is incorrect: does ~healthy necessarily imply unhealthy?? Can't something be ~healthy but still not "unhealthy" (ie, harmful?)

How about celery? Eating celery provides neither nutritional value
(in any meaningful way) nor caloric content. Yet, can we say that eating celery is necessarily unhealthy? I'm not quite prepared to make that leap yet. It's certainly ~healthy in the sense of not being healthy.

It seems like the elimination of (C) relies more on a (possibly) unwarranted linguistic assumption than any logical flaw. It also seems that this is an unfair question for that reason. Would someone please explain why I'm wrong?

[noah]

Here's the source of my confusion with the given explanations for why answer choice (C) is incorrect: does ~healthy necessarily imply unhealthy?? Can't something be ~healthy but still not "unhealthy" (ie, harmful?)

How about celery? Eating celery provides neither nutritional value
(in any meaningful way) nor caloric content. Yet, can we say that eating celery is necessarily unhealthy? I'm not quite prepared to make that leap yet. It's certainly ~healthy in the sense of not being healthy.

It seems like the elimination of (C) relies more on a (possibly) unwarranted linguistic assumption than any logical flaw. It also seems that this is an unfair question for that reason. Would someone please explain why I'm wrong?

Good question!

I looked back over my explanation and am not crazy about it -- thus about to edit it.

In short, does the application say that something is unhealthy? No, it just says that something is not healthy. Thus, there's no misinterpretation (as (C) suggests) of the principle to be about what is unhealthy.

That clear it up?

[smsotolongo]

Don't we have a term shift in the problem? The principle says "social development" and the application says "interacting." For this to be correct we have to assume all interacting leads to social development, therefore making D the flaw in the reasoning.

[BarryM800]

I initially thought the wording of the principle is ambiguous: "It is healthy for children to engage in an activity that promotes their intellectual development only if engaging in that activity does not detract from their social development." Specifically, the "only if" clause can be construed as modifying the main sentence "It is healthy, only if ..." and thus be construed as "for children to engage in an activity that promotes their intellectual development, it is healthy only if engaging in that activity does not detract from their social development."

(1) Children engage in activity promoting intellectual development: healthy → NOT detract from social development.

Or the "only if" clause can be construed as modifying the infinitive "to engage in an activity that promotes their intellectual development only if ... is healthy" and thus the main sentence is "It is healthy to ..."

(2) (Children engage in an activity promoting intellectual development → NOT detract from social development) → healthy. Apparently, once the conditional statement within the parenthesis is transformed into its contrapositive form, this construction does not make any sense: (Detract → NOT Children engage) → healthy.

So I'm wondering if there is any grammatical cue for us to go directly to the first interpretation, or maybe the rule of thumb is "only if" always goes to the main verb/sentence? Thanks!

[Misti Duvall]

I initially thought the wording of the principle is ambiguous: "It is healthy for children to engage in an activity that promotes their intellectual development only if engaging in that activity does not detract from their social development." Specifically, the "only if" clause can be construed as modifying the main sentence "It is healthy, only if ..." and thus be construed as "for children to engage in an activity that promotes their intellectual development, it is healthy only if engaging in that activity does not detract from their social development."

(1) Children engage in activity promoting intellectual development: healthy → NOT detract from social development.

Or the "only if" clause can be construed as modifying the infinitive "to engage in an activity that promotes their intellectual development only if ... is healthy" and thus the main sentence is "It is healthy to ..."

(2) (Children engage in an activity promoting intellectual development → NOT detract from social development) → healthy. Apparently, once the conditional statement within the parenthesis is transformed into its contrapositive form, this construction does not make any sense: (Detract → NOT Children engage) → healthy.

So I'm wondering if there is any grammatical cue for us to go directly to the first interpretation, or maybe the rule of thumb is "only if" always goes to the main verb/sentence? Thanks!

Sure! In conditional logic terms, "only if" = then. So you can substitute then anytime you see only if, and diagram it that way.