PrepTest 118, Section 1, Question 25
Some visitors to the park engage in practices(41 more words not shown)
The pattern of reasoning exhibited(17 more words not shown)
- ASome of the(30 more words not shown)
- BSome of the(28 more words not shown)
- CSome of the(33 more words not shown)
- DAll of the(33 more words not shown)
- ESome members of(33 more words not shown)
Reading the argument
What if some visitors know they're hurting the animals and do it anyway? That would be a fair concern in real life. But this argument expressly tells us that nobody who knows the practices are harmful would engage in them. For this question, we have to work with that premise.
Some visitors do engage in the harmful practices. Those visitors therefore cannot belong to the group who know about the harm: people in that group never engage in the practices. So some visitors must lack the knowledge. Once we accept both premises, the conclusion follows.
What we’re looking for
Now we're looking for the same pattern in another subject. Keep track of the people we start with: some visitors do a particular thing. A second group is ruled out from doing that thing. We conclude that some of the original visitors are outside that second group. The new argument needn't concern knowledge or animals, but it must preserve those relationships.
Working the answers
- A
The people who will be fired might all work outside this department. Everyone in the department worked on the project, but we don't know that the people selected for firing include any of them. A moves from some project workers to a particular subgroup without establishing the overlap. Our original conclusion follows; this one doesn't.
- B
This argument works, but it works differently. Some petition signers support the mayor. Since the mayor denounced every signer, she denounced those supporters too. We carry the denunciation over to a group included among the signers.
The original instead rules a group out: visitors who engage in the practices cannot be among those who know the harm. B doesn't have that exclusion leading to a conclusion that some people lack a property.
- CCorrect
Map the people first. Some people polled live outside the city, just as some park visitors engage in the harmful practices. People eligible to vote cannot live outside the city, just as people who know about the harm cannot engage in the practices.
Now follow the people identified by the first premise. The polled people outside the city cannot be eligible voters. Likewise, the visitors engaging in the practices cannot be people who know about the harm. Each conclusion excludes some members of the original group from the second group.
- D
This also reaches a valid conclusion, so validity alone won't choose the answer. All five planners are responsible, and none will admit responsibility. Those five people therefore give us examples of responsible people who won't admit it.
That's different from starting with some members of a larger group, then using a rule to exclude those members from another group. D directly gives all five planners both properties. We shouldn't reject it merely because it uses the word “all”; we should notice how its premises establish the result.
- E
We can conclude that the Liberals who favor the ordinance aren't council members, because every council member opposes it. But E concludes something about council members instead: that some are not Liberals. All council members could be Liberals who oppose the ordinance, while other Liberals favor it. E changes which group the conclusion concerns and no longer follows from the facts.
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