The word "only" in PT25-S4-23 Forum

[WaltGrace83]

I have no idea how the following conclusion from PT25-S4-Q23 is read the way it is:

"It follows that only those who appreciate these advances are computer scientists"
=
Computer Scientists → Appreciate Advances

http://www.manhattanlsat.com/forums/q23 ... 2125774930

Can someone please explain to me how this is so and what I am doing wrong here?

[Daily_Double]

Quick question that might resolve this entire issue without a bunch of words:

If I give you the following rule, assume it is true, The only people who watch the World Cup live in New York, and then you meet a girl named Jessica, who does not live in New York, what can you tell me about her World Cup viewing habits?

On the other hand, say you meet someone named Jeff from New York, do you know anything about his World Cup viewing habits?

And finally, say you meet someone (apparently you're making a lot of friend in this hypo) who watches the World Cup, where must he live?

[WaltGrace83]

Quick question that might resolve this entire issue without a bunch of words:

If I give you the following rule, assume it is true, The only people who watch the World Cup live in New York, and then you meet a girl named Jessica, who does not live in New York, what can you tell me about her World Cup viewing habits?

On the other hand, say you meet someone named Jeff from New York, do you know anything about his World Cup viewing habits?

And finally, say you meet someone (apparently you're making a lot of friend in this hypo) who watches the World Cup, where must he live?

(a) she doesn't watch the World Cup

(b) he has an opportunity to watch the World Cup, I suppose, but we don't actually know if he does

(c) New York

However, when I read the 25.4.23 conclusion, I just don't understand why it isn't AA --> CS. Usually I am fine with "only" but this one is baffling me for some reason and I have no idea why.

[Daily_Double]

However, when I read the 25.4.23 conclusion, I just don't understand why it isn't AA --> CS. Usually I am fine with "only" but this one is baffling me for some reason and I have no idea why.

Well you nailed the example and were really close to nailing this one.

What I'm going to do now is point out the general rule, then let's see how it applies to this specific question. In doing so we're going to hit a roadblock of sorts, which is when the general rule fails us and we have to actually think through the language to arrive at another rule of sorts---I swear there aren't enough of these questions.

GENERAL RULE/PATTERN: The only things that do X are Y

NOTATION: X ---> Y

This is what everyone is used to seeing. The reason behind this rule is that these people or things Y are the only group that does X, nobody else does. So whenever X is present, Y must be.

Now let's look at this question. I'm going to write out the conditions, then abbreviate them.

(1) The only people who Understand are Scientists
(2) The only people who Appreciate Advances are people that Understand
___________________________________________________________________________________
Thus, only the people who Appreciate Advances are Scientists

This is represented in such a way as to make it easy for you to apply the rule above. And that's easy until you get to the conclusion which is when you probably thought "What the hell is that 'the' doing after the word 'only,' it shouldn't there!" When you hit a situation like this on the test, pause for a moment, and literally think about what the words or phrases mean together. This sounds really simple, but it has to be a conscious act, otherwise you'll probably do something that you're used to doing that may not apply in that particular instance.

Now let's change the hypo I gave you earlier:

"Only the people who live in New York watch the World Cup."

Here we know that the people who live in New York are the only ones who watch the World Cup. Thus, living in New York is a requirement of viewing the World Cup. Same thing as we looked at earlier. Let's change the phrasing around to make this a bit more intuitive, then do the same with our conclusion:

"The people who live in New York are the only people who watch the world Cup."
"Only people living in New York watch the World Cup."

"The people who Appreciate Advances are the only people who are Scientists."
"Only people who Appreciate Advances are Scientists."

These phrases limit an occurrence to a specific group of people because they're the only ones who can have that quality. We can turn this into a rule of sorts:

RULE: Only the people doing X, do Y

NOTATION: Y ---> X

Again, the reasoning is that group X are the only people who do Y. Nobody but X does Y because if you do Y, then you must be in group X. Which leads us to the simplest way to think of this rule and that is since we know that an event (call it Y in the example above, or Computer Scientists in our actual question) is limited to a specific group (X or those who Appreciate Advances) we can drop the "the" and think of this as what it really is----doing Y requires X.

We have the exact same situation in this stimulus. Now let's look at this is an abbreviated form:

(1+2) Appreciate Advances ---> Understand Computers ---> Computer Scientist
____________________________________________________________
Thus, Computer Scientist ---> Appreciate Advances

Goddamn that Error of Conditional Logic is obvious.

[Brian_Wildcat]

I have no idea how the following conclusion from PT25-S4-Q23 is read the way it is:

"It follows that only those who appreciate these advances are computer scientists"
=
Computer Scientists → Appreciate Advances

http://www.manhattanlsat.com/forums/q23 ... 2125774930

Can someone please explain to me how this is so and what I am doing wrong here?

Think about it this way...

What can you say about people who don't appreciate the advances? well they aren't computer scientists

What can you say about people who do? well not much at this point because just appreciating the advances doesn't make them computer scientist automatically.

I don't know if that helps at all because I am failing to see the problem with the statement. It just helps to know that Only is a necessary indicator. I would just drill that in your brain. But, watch out for "THE only" that is a sufficient indicator.

[WaltGrace83]

I am still lost! When I see "Only those who appreciate these advances are computer scientists," I think "the only people who appreciate these advances are computer scientists" and thus "AA --> CS." I honestly just don't get this for some reason and this is frustrating.

EDIT: So is "the only..." different from "only the..."?

[Daily_Double]

I am still lost! When I see "Only those who appreciate these advances are computer scientists," I think "the only people who appreciate these advances are computer scientists" and thus "AA --> CS." I honestly just don't get this for some reason and this is frustrating.

EDIT: So is "the only..." different from "only the..."?

Yes. Haha, I might have obscured that point but that was the opposite of my intention.

"The only," is usually introduced away from the phrase it modifies. See the first part of my second post for examples.

"Only the," is usually introduced directly next to the phrase it modifies. You can just drop the word "the," and interpret this as "only," which is generally the easiest way to do this. See the second half of my second post for examples, reducing the phrase to "only," and the application of it to the question.

In both cases what you're really doing is finding what phrase is limited (the requirement) by asking yourself "what does the word only modify?" The notes on adjacent phrases are just general patterns.

[WaltGrace83]

So "only those who appreciate these advances are computer scientists" is really..."computer scientists appreciate ONLY advances." Thus, CS --> A (and nothing else)? I'd assume that "only the" is the same as "only those" or "only these" or "only that"

[Daily_Double]

So "only those who appreciate these advances are computer scientists" is really..."computer scientists appreciate ONLY advances." Thus, CS --> A (and nothing else)? I'd assume that "only the" is the same as "only those" or "only these" or "only that"

Now you are reading the rule too narrowly. What you've done here is limit scientists appreciation to advances and nothing else. When the rule merely establishes that scientists have a requirement----all scientists appreciate, or only people who appreciate are scientists.

[Brian_Wildcat]

So "only those who appreciate these advances are computer scientists" is really..."computer scientists appreciate ONLY advances." Thus, CS --> A (and nothing else)? I'd assume that "only the" is the same as "only those" or "only these" or "only that"

No I think you have it confused... that or you are confusing me haha.
Just because it is a necessary indicator does not mean it has to go at the end of the sentence. The way you wrote it the second time made no sense. you did translate it correctly though. It makes sense because if you were to say that I don't appreciate the advances you would fail the necessary and could conclude what?


On the second part I said "the only" not "only the"

[theotherone823]

What you are getting at here is the difference between what formal logicians would call "necessary conditions" and "sufficient conditions."

If A is a necessary condition of B, that means that in order for B to be true, A MUST also be true. A is necessary for B. A might not be the only condition that is required for B to be true, but there is no way for B to be true without A. The ONLY way for B to be true is if the condition of A was first met.

Symbolically this is diagramed as B->A, where A is the required condition and B is the outcome. Note here that when you diagram a relationship of a necessary condition, what you might think of as being the "effect" actually comes first in the diagram, before the arrow.

A perfect example of this is the classic idiom: "Where there is smoke, there is fire." Fire is a necessary condition of smoke and for there to be smoke there must first be fire. Symbolically this would be S->F.

If A is a sufficient condition of B, it means that A by itself is enough for B to true, but it is not the only path that you can use to get there. A MUST mean B, but C could also mean B.

One example of this would be US geography. If I am in NY, than I am in the United States. (Symbolically NY -> USA). But while being in NY is sufficient to be in the USA, it isn't necessary. Being in any other state, such as Texas, is also a possibility (TX -> USA).

To figure out if you are dealing with a necessary condition or a sufficient condition, try to determine if you are dealing with something that must be true for the outcome to also be true, in which case you have a necessary condition, or if it is just one of several possibilities that will lead to the outcome, in which case you have a sufficient condition.

With that in mind, does your statement: "It follows that only those who appreciate these advances are computer scientists" represent a necessary condition or a sufficient condition?

[Christine (MLSAT)]

So "only those who appreciate these advances are computer scientists" is really..."computer scientists appreciate ONLY advances." Thus, CS --> A (and nothing else)? I'd assume that "only the" is the same as "only those" or "only these" or "only that"

DD and Wildcat are knocking this out, but I thought I'd throw a few more examples in the ring to help you sort it:

The only person who can call me Chris is my mom.
Only my mom can call me Chris.

Both of these translate to: If you call me Chris --> you are my mom.

These are the essential examples of the difference between plain old 'only', and 'THE only'. I generally think of plain old 'only' as the typical case, as it's a lot easier to parse, and I think of 'the only' as the special, weird, broken-up sentence I have to be careful with.

Now, let's talk about different syntax constructions that do, grammatically, exactly the same thing as the plain old 'only' example:

Only my mom can call me Chris.
Only if you are my mom, can you call me Chris.
Only those people who are my mom can call me Chris.
Only the mom of me can call me Chris.

We can change "only" to "only if", "only those", "only the" (and probably some other things) and it doesn't change either the grammatical meaning or the logical meaning of the sentence. It all still translates to "If you call me Chris --> you are my mom."