Summarize Argument: Phenomenon-Hypothesis
A Geologist believes that Earth’s rate of rotation increased over the past decade due to a law of physics: as a spinning object’s radius decreases, its rate of rotation increases. The Geologist claims that the increase in the number and severity of earthquakes have caused the Earth’s tectonic plates to move toward the center of the Earth, causing the radius to decrease and the speed to subsequently increase.
Notable Assumptions
The author assumes that the movement of tectonic plates toward the center of the Earth outweighs any other factors that could cause the Earth’s radius to increase.
A
In the beginning of the twentieth century, geologists observed an increase in number and severity of earthquakes, accompanied by a decrease of Earth’s radius.
This supports the argument by bolstering the idea that earthquakes are causing the Earth’s radius to decrease.
B
During the past decade, other geological events have counteracted the movements of the tectonic plates that occur immediately after earthquakes.
This undermines one of the geologists' key assumptions: that another force did not counteract the decrease in the Earth’s radius from earthquakes. If this is true, the entire support of the argument is weakened, and its conclusion is called into question.
C
Only skillful figure skaters succeed in twirling faster by bringing their arms closer to their sides.
This is completely unrelated to the argument. The info about the skater is just context to explain how the law of physics works.
D
Since the time of the ancient Egyptians, Earth’s rate of rotation has been known to fluctuate.
If anything, this strengthens the argument by giving credence to the idea that the Earth’s rate of rotation changes. But it certainly gives nothing to weaken the argument.
E
Increased volcanic activity over the last ten years suggests that the overall movement of the tectonic plates has increased.
This does not say whether the tectonic plates are moving inward or outward. If anything, it is easiest to assume that the tectonic plates are moving inward, which would strengthen the argument, not weaken it.
Summary
The author concludes that the city council does not have the objective of preserving the quality and availability of local rentals. Why? Because the following:
The city council recently passed a rent-control ordinance.
A recent study shows that rent control increases the price and lowers the quality and availability of rental units.
The city council recently passed a rent-control ordinance.
A recent study shows that rent control increases the price and lowers the quality and availability of rental units.
Missing Connection
The conclusion asserts something about the city council’s purpose (objective). But the premises don’t say anything that establishes whether the city council has or doesn’t have the purpose of preserving the quality and availability of local rentals.
Even though the study shows that rent control will hurt the quality and availability of rentals, there’s no evidence that the city council believed that the study was accurate or was even aware of the study. To make the argument valid, we want to establish that the passage of the rent-control ordinance, in light of the recent study, allows us infer the council knew the rent-control ordinance would harm the quality/availability of local rentals.
Even though the study shows that rent control will hurt the quality and availability of rentals, there’s no evidence that the city council believed that the study was accurate or was even aware of the study. To make the argument valid, we want to establish that the passage of the rent-control ordinance, in light of the recent study, allows us infer the council knew the rent-control ordinance would harm the quality/availability of local rentals.
A
The recent study of local rent-control ordinances was conducted by impartial investigators.
(A) helps establish the reliability of the study. But it doesn’t establish that the city council knew about the study’s results or believed its findings. So it doesn’t establish anything about the city council’s objectives.
B
Rent control is not an appropriate topic for consideration by the city council.
What is or is not appropriate for the city council to consider does not establish anything about the city council’s objectives.
C
The members of the city council who voted for rent control agree with the study’s conclusions about rent control.
(C) establishes that the people who voted for the ordinance were aware of and agreed with the study’s conclusions. That establishes that the council’s objective was not to preserve the quality and availability of local rentals. After all, they knew that the ordinance would decrease the quality/availability of rentals, yet still passed it.
D
Some members of the city council who voted for rent control stand to profit from rent control.
The fact some members will profit from rent control does not establish that they voted to pass rent control for self-interested reasons. These members might have thought the rent control would increase the quality and availability of rentals.
E
The city council sometimes acts in an arbitrary and irrational manner.
The fact the council sometimes acts in an arbitrary/irrational manner doesn’t establish that with respect to this ordiance, it acted in an arbitrary/irrational manner.
Summarize Argument: Counter-Position
Professor Thomas says Professor York is too flamboyant and confrontational in the classroom. The author implicitly calls this claim into question by citing the fact that Thomas’s claim is self-serving. Thomas is not as good a presenter as York, so Thomas’s criticism of York may simply be a result of envy.
Identify and Describe Flaw
The author attacks Professor Thomas’s motivation rather than the merits of his claim. Whether Thomas is venting his frustration or otherwise making comments due to envy or out of self-interest has nothing to do with the truth of whether Professor York is actually too flamboyant or confrontational in the classroom.
A
confuses the distinction between being overly confrontational and engaging students by entertaining them
The author doesn’t mistake being too confrontational with being entertaining. There’s no sign that the author thinks one type of behavior is the same as the other.
B
presupposes the point it is attempting to establish
(B) describes circular reasoning. The author’s conclusion, which is an implicit questioning of Professor Thomas’s claim about Professor York, does not restate a premise.
C
mistakes Professor Thomas’s characterization of a view for an endorsement of that view
The author does not think Thomas endorsed anything that York did or said.
D
attacks Professor Thomas personally rather than addressing Professor Thomas’s argument
The author attacked Professor Thomas’s motivations rather than addressing the substance of Professor’s Thomas’s argument. We care about whether York is too flamboyant and confrontational. Thomas’s motive is irrelevant.
E
rejects the possibility that Professor York is in fact too confrontational
There’s a difference between rejecting Thomas’s conclusion that York is too confrontational and criticizing Thomas’s argument in favor of that conclusion. The author does the latter.