#25 - All actors are exuberant people and all exuberant

[Robert Carroll]

lola

Your diagramming was perfect, but incomplete. The final statement can be diagrammed:

shy people actors

Some shy actors exist, but all actors are exuberant, and all exuberant people are extroverts. Thus, those shy actors are exuberant extroverts as well. This is enough to establish their existence, so a "some" statement about them is appropriate.

A sufficient condition "trigger" exists whenever anything exhibits the sufficient condition. We're not saying all shy people are actors, but those who ARE actors will trigger the sufficient condition for themselves, and thus trigger the necessary conditions all along the chain.

"Some" means 1 to all inclusive (just clarifying). Answer choice (C) is not saying that all exuberant people who are actors are shy - it's just saying some (so 1 to all) exist. The objection that "some" does not necessarily mean "all" is inapt - "some" doesn't necessarily mean "all", but it certainly doesn't contradict it. Nor is "some" inappropriate when you know not all people have a certain quality: "Some people are children" and "Some people are adults" are perfectly consistent with each other.

One thing to note: you cannot infer that "some actors who are exuberant are not necessarily shy." It's compatible with the stimulus that all actors be shy. We don't know it's true, but, importantly, we also don't know that the opposite is true.

Robert Carroll

[alainacohen]

Hello,

I was wondering if you could explain why the double arrow was used for shy actors? I understand the concept of biconditionals (each term is both sufficient and necessary for the other), but I am not understanding why it was used in this case? Although I do understand why B is the correct answer choice, I am not understanding why E is not a mistaken reversal and, therefore, and also not the correct answer choice (which is probably because I am not understanding the double arrow). Thank you so much for your help!

[Rachael Wilkenfeld]

Hi alainacohen,

The "some" arrow is reversible because of the nature of the term "some." If some dogs are brown, it means both that there is at least one brown thing that is a dog, and at least one dog that is brown. Our stimulus says that some shy people are actors. That means that there is at least one shy person who is an actor, and that at least one actor is shy. Answer choice (E) is something that has to be true because the "some" shy person that is an actor, also must be exuberant and must be an extrovert.

As a formal logic aside, in case you are curious, the term "none" also is reversible. If no dogs are cats, no cats are dogs. If you happen to have the Logical Reasoning Bible, chapter 13 covers formal logic in a lot of detail.

Hope that helps!
Rachael

[ashpine17]

How do you diagram answer choice C?

[Robert Carroll]

ashpine,

(exuberant + actor) shy

Robert Carroll

[tkkim7]

I'm having trouble understanding how C is correct.
doesn't Actors exuberant entail Actors exuberant?
Then if you were to combine that with Shy people actors, wouldn't the diagram be
Shy people actors exuberant ? If so how does C follow? I remember the LR Bible stating that the Some Train can be used to cross over only when there is an all arrow or a biconditional. But since there are two some arrows connecting the diagram I don't see how we can go from exuberant to shy people? Thanks!

[tkkim7]

I meant I don't understand how C can be true!

I'm having trouble understanding how C is correct.
doesn't Actors exuberant entail Actors exuberant?
Then if you were to combine that with Shy people actors, wouldn't the diagram be
Shy people actors exuberant ? If so how does C follow? I remember the LR Bible stating that the Some Train can be used to cross over only when there is an all arrow or a biconditional. But since there are two some arrows connecting the diagram I don't see how we can go from exuberant to shy people? Thanks!

[Dana D]

Hey Tk,

If Actors exuberant then some exuberant people are actors yes, but we wouldn't want to write the rule like this because if we write Actors exuberant than we are implying that not all actors are exuberant - and that's not what the stimulus is saying.

If we add shy people into the mix, then we get Shy Actors Exuberant Extroverts.

So if you follow that logic, at least one person can be shy, be an actor, and therefore be exuberant as well.

[tkkim7]

Thank you! It makes much more sense now.

Hey Tk,

If Actors exuberant then some exuberant people are actors yes, but we wouldn't want to write the rule like this because if we write Actors exuberant than we are implying that not all actors are exuberant - and that's not what the stimulus is saying.

If we add shy people into the mix, then we get Shy Actors Exuberant Extroverts.

So if you follow that logic, at least one person can be shy, be an actor, and therefore be exuberant as well.