One is likely to feel comfortable approaching a stranger if the stranger is of one's approximate age. Therefore, long...

Mehran on May 21, 2016

@sydbrown6 let's take a look.

This stimulus is an argument that can be broken down as follows:

P1: One is likely to feel comfortable approaching a stranger if the stranger is of one's approximate age.

We know "if" introduces sufficient so we can actually diagram P1 as follows:

OAA ➡️ FCAS
not FCAS ➡️ not OAA

P2: Most long-term friendships begin because someone felt comfortable approaching a stranger.

This is a quantifier that we can write out as follows:

LTF-most-FCAS

C: Long-term friends are probably of the same approximate age as each other.

This is also a quantifier that the author is attempting to create by combining P1 and P2.

The problem here is that the variable P1 & P2 share in common is FCAS (i.e. felt comfortable approaching stranger), but FCAS is our necessary condition in P1 so we cannot make a valid deduction here.

The author is assuming that P1 actually says FCAS ➡️ OAA (contrapositive not OAA ➡️ not FCAS).

The author is overlooking the possibility (i.e. failing to address) that a person who might not be a stranger's approximate age would nevertheless feel comfortable approaching that stranger.

Notice that according to P1, this is entirely possible because not OAA is negating the sufficient condition and we know that the negation of the sufficient condition tells us nothing (i.e. don't just negate!).

Hope this helps! Please let us know if you have any other questions.

sydbrown6 on May 22, 2016

Thank you!

Reina on March 27, 2020

@mehran can you explain how the answer choice fits in with the diagram? I diagrammed the question correctly but I'm not sure how to apply it to an answer choice

Skylar on June 22, 2020

@Reina, happy to help!

The argument concludes that most long-term friends are probably the same age. Why? Because most long-term friendships begin because someone felt comfortable approaching a stranger, and we are told that if you are of the same approximate age as a stranger, then you are likely to feel comfortable approaching them.

Notice the flaw in this- we know that you are likely to feel comfortable approaching a stranger if you are of their approximate age. If you are not of their approximate age, we have no idea how you feel approaching a stranger (because FCAS is our necessary condition, as Mehran explained via the above diagrams). Perhaps you are comfortable doing so, in which case you could form a long-term friendship and would not be of the same age. In other words, the argument is too limited to support its own conclusion because it does not consider situations in which you are not the same age as a stranger. (E) is correct because it points this out.

Does that make sense? Hope it helps! Please let us know if you have any other questions!