Summarize Argument
Renting a car from dealerships instead of national rental firms benefits local residents more than tourists. Residents can benefit from dealerships’ lower rates without dealing with the disadvantages tourists face.
Notable Assumptions
The author assumes that there are no other significant perks to renting from a dealership that a tourist would enjoy that could potentially make renting from a dealership more worthwhile.
A
To encourage future business, many car dealerships drop off and pick up rental cars for local residents at no charge.
This strengthens the argument by providing an extra perk that dealerships offer to local residents. We already know why local residents like dealerships—this just makes it better.
B
Tourists renting cars from national rental firms almost never need to pay for taxi rides to or from the airport.
This strengthens the argument by providing another reason why renting from a dealership is less worthwhile for a tourist. If they rented from a dealership they’d have to pay for a taxi from the airport. Renting from a rental firm saves them this cost.
C
Travel agents generally are unable to inform tourists of which local car dealerships offer rentals.
This strengthens the argument by offering support for the premise that tourists must determine which dealerships offer rentals—travel agents are unable to provide information, and tourists must research it themselves.
D
Many local residents know of local car dealerships that offer low-priced rentals.
This strengthens the argument by providing another reason why dealerships are more worthwhile for local residents: they already know which dealerships offer cheap rentals.
E
For local residents, taxi rides to car dealerships from their homes or workplaces are usually no less expensive than taxi rides to national rental firms.
This weakens the argument by attacking the idea that tourists are more disadvantaged than local residents by the cost of commuting to pick up their rental car. (E) says local residents also face this issue, and that dealerships don’t actually benefit local residents in this way.
Summarize Argument
The author concludes that there are some days when both of the following occur: (1) the wind blows into Hillview from the east, and (2) the smog in Hillview reaches unsafe levels. This is based on the fact that there are some hot days on which the smog in Hillview reaches unsafe levels, and that there are some hot days on which the wind blows into Hillview from the east.
Identify and Describe Flaw
The author assumes that some of the hot days on which the smog reaches unsafe levels are the same hot days on which the wind blows in from the east. This overlooks the possibility that the hot days on which the smog reaches unsafe levels are simply different days from the hot days on which the wind blows in the from east.
If “Some A are B” and “Some A are C,” we cannot conclude “Some B are C.” This is because B and C might not overlap within the set of A.
A
mistakes a condition that sometimes accompanies unsafe levels of smog for a condition that necessarily accompanies unsafe levels of smog
The author does not assume that anything “necessarily accompanies” unsafe levels of smog. The author believes that some days with unsafe smog levels are days on days with the east wind, but that doesn’t imply unsafe smog is always accompanied by east wind.
B
fails to recognize that one set might have some members in common with each of two others even though those two other sets have no members in common with each other
The author fails to recognize that although the set of “hot days” has some days in common with the “unsafe smog days” and some in common with “east wind days,” the “unsafe smog days” and “east wind days” don’t have to have any days in common.
C
uses the key term “unsafe” in one sense in a premise and in another sense in the conclusion
The word “unsafe” does not take on different meanings in this argument. It means “not safe.”
D
contains a premise that is implausible unless the conclusion is presumed to be true
(D) describes circular reasoning, which isn’t what happens here. Accepting the premises does not require that we already accept there are some days with both unsafe smog and east wind.
E
infers a particular causal relation from a correlation that could be explained in a variety of other ways
The argument does not assert any causal relationships. The claim that there are some days that have both the east wind and unsafe smog does not assert that the east wind causes smog to be blown in or that the smog causes the east wind.
Quincy: I am skeptical that the association between the lights and the earthquakes is anything more than a coincidence. The theory that ground stresses related to earthquakes can cause any kind of lightning is extremely speculative.
Summarize Argument: Counter-Position
Quincy concludes that Phoebe’s explanation of strange glowing lights as earthquake-induced is unconvincing. This is supported by the claim that the mechanism Phoebe proposes for her explanation—ball lightning forming as a result of ground stresses—is “extremely speculative.”
Describe Method of Reasoning
Quincy counters Phoebe’s argument by casting doubt on the mechanism she proposes to explain a phenomenon. By pointing out that earthquake-related ground stresses are not known to cause any kind of lightning, Quincy undermines Phoebe’s conclusion that the strange lights were “almost certainly” caused by earthquakes.
A
takes a correlation to be a causal relation
Quincy doesn’t say that any causal relationship exists based on a correlation. In fact, he’s arguing against Phoebe’s claim that a causal relationship exists.
B
challenges the accuracy of the data about sightings that Phoebe takes for granted
Quincy doesn’t challenge the accuracy of any of Phoebe’s data about the sightings. He accepts that the sightings have happened; he only doubts her explanation for the phenomenon.
C
criticizes Phoebe’s explanation as unsubstantiated
Quincy criticizes Phoebe’s explanation of strange glowing lights being ball lightning caused by earthquakes, because it is founded on a speculative—meaning unsubstantiated—theory about the potential of earthquakes to cause lightning.
D
offers an explanation of the glowing lights different from Phoebe’s
Quincy doesn’t offer any alternative explanation of the glowing lights, only casts doubt on the plausibility of Phoebe’s explanation.
E
accuses Phoebe of introducing irrelevant information
Quincy doesn’t claim that Phoebe has introduce any irrelevant information, only that she has interpreted the information in a questionable way based on speculative theories.
Summary
While some people claim that laws are enacted at least in part to establish a moral fabric in society, the primary purpose of law is to establish order within society. Why? Because sometimes the highest courts have treated moral beliefs as grounds for exceptions in the application of laws.
Strongly Supported Conclusions
Sometimes the application of law involves factoring in people’s moral beliefs.
A
The manner in which laws are applied sometimes takes into account the beliefs of the people governed by those laws.
The stimulus tells us that sometimes the highest courts use moral beliefs as grounds for making exceptions in their decisions. If this is true, then it must be that there are at least some instances where people’s beliefs are considered when applying the law.
B
The law has as one of its functions the ordering of society but is devoid of moral aims.
We don’t know whether moral aims are completely absent from the law. We only know that the law’s primary purpose is establishing order within society. It could be the case that moral aims are a secondary purpose.
C
Actions based on religious belief or on moral conviction tend to receive the protection of the highest courts.
We don’t know whether actions taken due to a person’s moral beliefs usually receive protection from the highest courts. In the stimulus, we are only told that using moral beliefs as grounds for decisions are the exception when courts apply the law.
D
The way a society is ordered by law should not reflect any moral convictions about the way society ought to be ordered.
We don’t know what way society should be ordered by law. There is no value judgement in the stimulus.
E
The best way to promote cooperation among a society’s institutions, organizations, and citizenry is to institute order in that society by means of law.
We don’t know what the best way to establish order within a society would be. There is no value judgment in the stimulus.
Summary
The stimulus can be diagrammed as follows:
Notable Valid Inferences
Most speed readers have above-average intelligence.
A
Some people can speed-read, and are able to fully concentrate, but are of below-average intelligence.
This must be false. We know that all people who are able to fully concentrate are of above-average intelligence.
B
All people who can speed-read are of above-average intelligence.
This could be true. We know for sure that most speed readers are of above-average intelligence; it could still be true that all are of above average intelligence.
C
Many people of above-average intelligence are unable to fully concentrate.
This could be true. We know that all people who can fully concentrate are of above-average intelligence, but this doesn’t mean that everyone of above-average intelligence can fully concentrate.
D
Some people with little ability to concentrate are of below-average intelligence, but can speed-read.
This could be true. If someone of is below-average intelligence, then they can’t fully concentrate. It could totally be the case that this person has the ability to speed read.
E
All people who can speed-read are able to concentrate to some extent.
This could be true. The only factor related to concentration discussed in the stimulus is “full concentration;” it could be the case that all people who can speed read can concentrate at least a little bit.
A
a nation that fails to invest in its infrastructure need not experience any resulting decline in its standard of living
The author’s conclusion is about a nation experiencing a rise in its standard of living as a result of investment in its infrastructure, not a decline in standard of living as a result of failing to invest in infrastructure.
B
many nations are unable to make the needed investments in infrastructure
Like (C) and (E) this may be true, but it doesn’t impact the author’s argument. Even if many nations can’t invest in infrastructure, it doesn’t affect the conclusion that such investments are necessary for a higher standard of living.
C
the rise in a nation’s standard of living that is prompted by investment in its infrastructure may take a long time to occur
Like (B) and (E) this may be true, but it doesn’t impact the argument. Even if the rise in standard of living takes a long time, it doesn’t affect the conclusion that investments in infrastructure are necessary for it to occur. The author even notes that it happens “over time.”
D
a rise in a nation’s standard of living need not be the result of major investments in its infrastructure
The author mistakenly assumes that investments in infrastructure are necessary, rather than merely sufficient, for a nation to experience a rise in its standard of living. But a nation’s standard of living could improve for other reasons, without investments in infrastructure.
E
nations often experience short-term crises that require that resources be diverted to purposes other than the maintenance and improvement of infrastructure
Like (B) and (C) this may be true, but it doesn’t impact the argument. Even if a nation can’t invest in infrastructure, it doesn’t affect the conclusion that such investments are necessary for a higher standard of living.
Campisi: I find your inference unconvincing; several leavens other than yeast could have been known in 1200 B.C.
Summarize Argument: Counter-Position
Campisi concludes that Yang is not justified in inferring that yeast was known as a leaven in 1200 B.C. just because leavens were known at that time. Why? Because, according to Campisi, other leavens than yeast could have been known in 1200 B.C.
Describe Method of Reasoning
Campisi undermines Yang’s conclusion by introducing an alternative explanation to account for Yang’s evidence. The evidence only shows that some unspecified leaven was used in 1200 B.C., so by pointing out the possibility that other leavens than yeast could have been known at that time, Campisi offers an alternative explanation.
A
suggesting that an alternative set of evidence better supports Yang’s conclusion
Campisi isn’t trying to support Yang’s conclusion, but rather to undermine it. Also, Campisi never proposes alternative evidence.
B
questioning the truth of a presumption underlying Yang’s argument
Yang presumes that there are no alternative leavens other than yeast that could have been known in 1200 B.C. By introducing other leavens as an alternative explanation for Yang’s evidence, Campisi questions that presumption.
C
denying the truth of Yang’s conclusion without considering the reason given for that conclusion
Campisi does consider the evidence behind Yang’s conclusion, and rejects its support for Yang’s conclusion on the grounds that there are alternative explanations available. Also, Campisi never denies the truth of Yang’s conclusion—unsupported doesn’t mean false.
D
pointing out that the premises of Yang’s argument more strongly support a contrary conclusion
Campisi does not argue that another specific conclusion is supported by Yang’s premises, only that Yang’s conclusion is not convincing based on its premises.
E
calling into question the truth of the evidence presented in Yang’s argument
Campisi does not question the evidence that a leaven was known in 1200 B.C., only offers alternative possible explanations for that evidence in order to question Yang’s conclusion.