QUESTION TEXT: In the Riverview Building, every apartment that…
QUESTION TYPE: Flawed Parallel Reasoning
CONCLUSION:
One Bedroom ➞ ~Fireplace
REASONING: Balcony ➞ Fireplace
Balcony ➞ ~One Bedroom
ANALYSIS: This argument mixed up necessary and sufficient conditions. Having a balcony is sufficient to have a fireplace, but it isn’t necessary. There can be apartments with fireplaces and no balconies.
It’s possible that every apartment has a fireplace.
Structurally, the argument takes both necessary conditions and combines them, incorrectly.
Note that the translation for ‘No politician is honest’ is P ➞ ~H. You negate the necessary condition.
___________
- Fish ➞ Fur – Conclusion
Cat ➞ Fur
Cat ➞ ~Fish This is a strange argument, but it doesn’t mix up sufficient and necessary. Note that the necessary conditions weren’t combined in the same way. Neither is negated in this conclusion. - Rule this out right away; it uses a ‘some’.
- CORRECT. Dog ➞ ~Fur – Conclusion
Cat ➞ Fur
Cat ➞ ~Dog This mistakenly assumes that Cat is necessary for Fur, because Cat is sufficient. Note also that the two necessary conditions have been used to make a statement. - Cat ➞ Fish – Conclusion
Cat ➞ ~Dog
Dog ➞ ~Fish Nonsense, but no sufficient-necessary error. - Fish ➞ ~Dog – Conclusion
Dog ➞ Mammal
Fish ➞ ~Mammal This is a good argument!
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MemberConnor Thornton says
Hi Graeme,
When you are doing this question or one like it, do you write out all the diagrams? I assume not, you probably visualize it. But, would analyzing the structures of both to narrow down the options then diagramming if necessary be the optimal strategy?
FounderGraeme Blake says
I think on this one I drew the setup and probably none of the answers but would have been prepared to draw 1-2 if needed.
MemberFarheen says
Hey Graeme,
Your explanations are pretty awesome. They are extremely helpful due to their simplicity of analysis. However, i think you should review this question. The conclusion as stated is wrong and so is the note i believe. The conclusion says: 1B—-> No fireplace. I am guessing that your note should say, No politician is honest= P——> Not Honest.
If otherwise i would like to know please.
TutorLucas (LSAT Hacks) says
It’s great to hear that you’ve gotten so much from Graeme’s explanations! And thanks for catching those small typos in the explanation. The page has been updated.