PT13.S4.Q14 - some of the world's most beautiful cats

piotr.borowski

Dear 7sage community,
Could someone please explain to me why answer E is correct? I can justify eliminating answers A,B,C,D, but not picking E. Most of all, I cannot comprehend how to apply the 'can be false' principle to a statement containing 'some' and a negation ('not'). By now my brain hurts from all the theories I tried to convince myself of.
Thanks a lot!

Accounts Playable

This is a must be true/inference EXCEPT question, so 4 answer choices are valid inferences while one answer choice either must be false or it isn't provable.

Essentially, we have one long chain:
World's most beautiful cats SOME Persian--->Pompous--->Irritating

What I am looking for: The SOME statement is pretty early in the chain, so we have a ton of SOME inferences.

Answers A-D are all valid inferences.

Answer E is an invalid inference, and it doesn't have to be true. It could be true or it could be false; we don't have enough information to make this a valid inference.

You can eliminate this because we don't know anything about Not Persian cats. Failing the sufficient condition makes all of the "arrow" conditional rules irrelevant. Since you can't take the contrapositive of a SOME statement, the Not Persian doesn't push back. It could be the case that all of the beautiful cats are Persian (since "all" could mean "some").

piotr.borowski

Thanks a lot for helping!
Could you please comment on one of my attempts to understand the statement in answer E?
Let's assume that the statement 'Some irritating and beautiful cats are not Persian cats' is false (since, according to my understanding, that is the condition for E's being the correct answer). If it is false, then we have the following statement: 'No irritating and beautiful cats are not Persian cats' (No/none being the negation of some), which equals to 'All irritating and beautiful cats are Persian cats'. In light of the information contained in the stimulus, such a statement is false. Therefore, the statement 'Some irritating and beautiful cats are not Persian cats' cannot be false, since assuming that it is leads us to a statement that is incorrect.
I know that there is only one correct answer to question 14, and that is E. The reasoning that I have presented above must therefore be unsound. Could you please explain to me where I have made a mistake?
Many thanks

Accounts Playable

The answer to this question doesn't need to be false since the question asks us "each of the following must also be true on the basis of them EXCEPT"; the correct answer could just be not provable based on the stimulus. Answer E could actually be a true statement, but we aren't given enough information to conclude one way or another, so on the basis of the facts, it doesn't have to be true.

It could actually be the case that some irritating and beautiful cats are not Persian cats; it could also be the case that all irritating and beautiful cats are Persian cats. We just don't know if we are to use only the information given to us. For these types of questions, it isn't all that helpful to negate answer choices because the incorrect answers are all provable while the incorrect answer isn't. Since answer E isn't a valid inference, and for that reason alone, it is the correct answer.

piotr.borowski

I think I just got it. 'All irritating and beautiful cats are Persian cats' is not incorrect from the point of view of the stimulus, since 'all' is part of 'some'

piotr.borowski

Thanks a lot for your explanation, it helps a lot!