Q2 - John: For 40 years, flouride

[wgutx08]

The argument said "ONLY then will I be sure not to develop cancer". Without this "ONLY", I would of course have picked E. But with "ONLY", John is setting not drinking Fl-water as a necessary but not sufficient condition for not developing cancer? So although this statement has many potential flaws, E is not one of them? Or should this ONLY be understood as :then and only then"?

After eliminating E, I then went back to the argument and thought that the MAIN conclusion is "I should stop drinking Fl-water". so Although D has nothing to do with the argument process, it is indeed a flaw for the main conclusion.

Can some Geek/Peer explain this to me? Quite frustrated right now.

[tommywallach]

Hey Wgutx,

Let's start by looking at the core.

Conclusion: The only way John can be certain not to develop bone cancer is to stop drinking fluoridated water.

Premise: Fluoridated water gave bone cancer to 90% of male rats.

The problem with this argument is two-fold:

1) John assumes there isn't some other way to prevent the development of bone cancer.

2) John assumes that he can be certain not to develop bone cancer, which is obviously too extreme.

Now let's look at the answers:

(A) is out of scope because it discusses other people.
(B) is out of scope because it discusses other diseases (notice our conclusion and premise are both about only bone cancer).
(C) is about the past, which we don't care about.
(D) is way out of scope. We don't care about positive effects, and we definitely don't care about other people.
(E) is CORRECT. It relates to our second assumption. Just because John won't get bone cancer because of fluoride, he could get it some other way.

Hope that helps!

-t

[aznriceboi17]

Hi tommywallach, I had the same question that wgutx08 had regarding the conclusion:

Conclusion: The only way John can be certain not to develop bone cancer is to stop drinking fluoridated water.

Is this a statement of a necessary condition? In other words:

John can be certain not to develop bone cancer => John stopped drinking fluoridated water

Even though this doesn't necessarily impact the selection of the right answer, I was also really thrown off by the wording. The other interpretation is that the 'only then' in the stimulus is essentially an 'if and only if' statement:

John can be certain not to develop bone cancer <=> John stopped drinking fluoridated water

I was drawn to this interpretation by temporarily dropping the 'only', because what's left then seems very much like an if-then statement:

I should nevertheless stop drinking fluoridated water; then will I be sure not to develop bone cancer.

The LSAT official solutions seem to use the second interpretation, since they say 'John concludes that if he stops drinking flouridated water he can make sure that he won't develop bone cancer.', which is one half (the 'if' part) of the 'if and only if statement'.

If that's the case, that is the sentence 'I should do A; only then will B happen.' means 'A if and only if B', then I'll have to make a mental note to remember that since it seems confusing.

[tommywallach]

Hey Azn,

Basically, the conclusion as written wants to be a sufficient condition, but the premise given doesn't even make it a necessary condition (you don't HAVE to stop drinking fluoridated water not to develop bone cancer, because there could be some way to counteract the effect of drinking the water). As written, however, the conclusion is indeed jumping to a sufficient condition: not drinking fluoridated water is concluded to be sufficient for not getting bone cancer.

Does that answer your question?

-t

[aznriceboi17]

Hi tommywallach, thanks for the response!

A = not drink fluoridated water
B = be sure not to develop bone cancer

I think I follow you when you say that the conclusion, as stated, presents A as a sufficient condition for B.

But does the 'only then' part not also make A a necessary condition for B? I.e., the conclusion as stated is A if and only if B?

I think this is compatible with what you said about

but the premise given doesn't even make it a necessary condition

since here we're only talking about what the conclusion is saying, and not what is supported by the premises/argument. However, I wanted to double check.

[ohthatpatrick]

This is weird when it comes to conditional logic triggers ... easier to read and react to this one as a normal, conversational human. When I first read this argument, without thinking about conditional logic or diagramming, my gut reaction was, "Say what?! You’re SURE you’re not going to develop bone cancer? Just because you eliminate one potential cause of cancer from your life doesn’t mean you’re not vulnerable to others!"

Only through reading this thread did I notice the other flaw, which is that John also believes that getting rid of fluoridated water is the ONLY way he can avoid cancer.

The conclusion gives us a bi-conditional statement because "only then" conveys that "quitting fluoridated water" is NECESSARY and "will I be sure" conveys that "quitting fluoridated water" is SUFFICIENT.

If you focus on the ONLY THEN, you might naturally agree that this author believes:

if I don’t quit fluoridated water, I will still be at risk of bone cancer.

If you focus on the THEN WILL I BE SURE, you might hear the author saying:
if I do quit fluoridated water, I will be sure not to develop bone cancer

Since those two look, more simply, like this:
~ Quit Flor. Water "”> Risk of bone cancer
and
Quit Flor. Water "”> ~Risk of bone cancer

We have a bi-conditional statement.

I wouldn’t dwell on the "I better memorize this unique formulation for the sake of my diagramming rules". I’ve seen thousands of questions and I’ve never needed to care about this formulation before. Instead, I would make my takeaway, "if I’m having a hard time diagramming something, let me engage with it conversationally and see if I can restate the person’s beliefs some other way."

[jm.kahn]

This is weird when it comes to conditional logic triggers ... easier to read and react to this one as a normal, conversational human. When I first read this argument, without thinking about conditional logic or diagramming, my gut reaction was, "Say what?! You’re SURE you’re not going to develop bone cancer? Just because you eliminate one potential cause of cancer from your life doesn’t mean you’re not vulnerable to others!"

Only through reading this thread did I notice the other flaw, which is that John also believes that getting rid of fluoridated water is the ONLY way he can avoid cancer.

The conclusion gives us a bi-conditional statement because "only then" conveys that "quitting fluoridated water" is NECESSARY and "will I be sure" conveys that "quitting fluoridated water" is SUFFICIENT.

If you focus on the ONLY THEN, you might naturally agree that this author believes:

if I don’t quit fluoridated water, I will still be at risk of bone cancer.

If you focus on the THEN WILL I BE SURE, you might hear the author saying:
if I do quit fluoridated water, I will be sure not to develop bone cancer

Since those two look, more simply, like this:
~ Quit Flor. Water "”> Risk of bone cancer
and
Quit Flor. Water "”> ~Risk of bone cancer

We have a bi-conditional statement.

I wouldn’t dwell on the "I better memorize this unique formulation for the sake of my diagramming rules". I’ve seen thousands of questions and I’ve never needed to care about this formulation before. Instead, I would make my takeaway, "if I’m having a hard time diagramming something, let me engage with it conversationally and see if I can restate the person’s beliefs some other way."

Even the superprep explanation is confusing for this question and I think this question has a mistake. In the bolded part, how can "i will be sure" introduce a sufficient condition?

The way conclusion reads, "only then" connects "stop drinking fluoride water" (necessary condition) with "I will be sure to not develop bone cancer" (sufficient condition).

And "only then" simply introduce a sufficient condition.

Superprep explanation glosses over this issue and refers to the conclusion in 2 different contradictory ways ("azn" poster above has mentioned this).

1. "Stop drinking fluoride water is the only way to make sure John won't develop bone cancer." (here "stop drinking fluoride water" is NC)
2. "If john stops drinking fluoride water, he can make sure he won't develop bone cancer". (here "stop drinking fluoride water" is SC)

Would lsat geeks/experts agree that justifying a bi-conditional here seems more like justifying a mistake by lsac?

[LolaC289]

The conclusion gives us a bi-conditional statement because "only then" conveys that "quitting fluoridated water" is NECESSARY and "will I be sure" conveys that "quitting fluoridated water" is SUFFICIENT.

IF the last sentence is "THEN AND only then will I be sure..." instead of "only then will I be sure", I will have no doubt in this as a bi-conditional statement.

However, I'm just not sure if the original sentence should be interpreted that way. It makes sense, but so does interpreting it as only a necessary condition, right? It is ambiguous and seems to go both ways. I can almost hear this question writer yelling to those who doubt this question :"don't you see I deliberately put the weird 'will I be sure' in the sentence? " It just makes me feel gimmicky.

Also, (D) actually make sense if we see the "only then" sentence as a necessary condition introducer. From NOT stop drinking fluoridated water may cause bone cancer (the contrapositive of the "only then" sentence), the author arrived at he SHOULD NOT drink it at all. But there maybe some positive effects from drinking fluoridated water that, once removed, will hurt human health even more.

Again, it all starts with this "only then WILL I BE SURE" ......

[LolaC289]

The conclusion gives us a bi-conditional statement because "only then" conveys that "quitting fluoridated water" is NECESSARY and "will I be sure" conveys that "quitting fluoridated water" is SUFFICIENT.

IF the last sentence is "THEN AND only then will I be sure..." instead of "only then will I be sure", I will have no doubt in this as a bi-conditional statement.

However, I'm just not sure if the original sentence should be interpreted that way. It makes sense, but so does interpreting it as only a necessary condition, right? It is ambiguous and seems to go both ways. I can almost hear this question writer yelling to those who doubt this question :"don't you see I deliberately put the weird 'will I be sure' in the sentence? " It just makes me feel gimmicky.

Also, (D) actually make sense if we see the "only then" sentence as a necessary condition introducer. From NOT stop drinking fluoridated water may cause bone cancer (the contrapositive of the "only then" sentence), the author arrived at he SHOULD NOT drink it at all. But there maybe some positive effects from drinking fluoridated water that, once removed, will hurt human health even more.

Again, it all starts with this "only then WILL I BE SURE" ......