PrepTest 138, Section 3, Question 24
In the Riverview Building, every apartment that has(25 more words not shown)
The flawed nature of the(17 more words not shown)
- Aevery fish has(12 more words not shown)
- Bsome cats lack(12 more words not shown)
- Cno dog has(12 more words not shown)
- Devery cat is(14 more words not shown)
- Eno fish is(14 more words not shown)
Reading the argument
A balcony gets you a fireplace. Why should it be the only way to get one?
Every balcony apartment has a fireplace, and no balcony apartment is a one-bedroom. So the one-bedrooms don't have balconies. Fine. But they could still have fireplaces. For all we've been told, every apartment in the building could have a fireplace, with balconies available in only some of them.
What we’re looking for
The argument treats membership in the balcony group as required for the fireplace, even though the premise only guarantees fireplaces for that group. To demonstrate the same error, match three roles: a group whose members all have a feature, another group excluded from the first, and an unsupported conclusion that none of that second group has the feature.
Working the answers
- A
Cats take the role of balcony apartments, fur takes the role of fireplaces, and fish take the role of one-bedroom apartments. The premises line up: all cats have fur and no cat is a fish. But the conclusion goes the opposite way, giving every fish fur. Our argument denies fireplaces to the entire excluded group. A assigns the feature to that group instead.
- B
Here dogs have the feature, fur, and cats are outside the dog group. Those premises could take the same roles as balcony apartments, fireplaces and one-bedrooms. But the conclusion says some cats lack fur. The original concludes that none of the excluded group has the feature. B's claim about some members is weaker and doesn't reproduce that full exclusion.
- CCorrect
Cats correspond to balcony apartments; dogs correspond to one-bedroom apartments; fur corresponds to fireplaces. Every cat has fur, and no cat is a dog. Yet it doesn't follow that no dog has fur. Dogs could have fur without being cats, just as one-bedrooms could have fireplaces without having balconies. C makes the same unsupported move from being outside one group to lacking a feature of that group.
- D
The premises separate cats from dogs and dogs from fish. That doesn't establish that every cat is a fish. Unlike the original, this doesn't begin by giving one group a feature and then deny that feature to a separate group. It turns two exclusions into a claim that one group belongs entirely to another.
- E
This reasoning works. Every dog is a mammal, while no fish is a mammal. A fish therefore cannot be a dog, because being a dog requires being a mammal. Here the excluded property is actually required for membership in the target group. In the apartment argument, having a balcony was never established as a requirement for having a fireplace.
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