Summarize Argument: Counter-Position
The astronomer considers an argument held by many people and concludes that it is possible to have both well-lighted streets and relatively dark skies. As evidence, the astronomer points out that in Sandsville the local observatory’s view is clear because the city has both restricted unnecessary lighting and installed street lamps that direct all light downward.
Describe Method of Reasoning
The astronomer counters a position held by others. She does this by offering a counterexample. It is not true that interference from lights is inevitable because in Sandsville relatively dark skies are achieved by restricting unnecessary lighting and installing special street lamps.
A
appealing to a scientific authority to challenge a widely held belief
The astronomer does not appeal to a scientific authority. We cannot assume that just because the argument is made by an astronomer that the argument appeals to scientific authority.
B
questioning the accuracy of evidence given in support of the opposing position
The astronomer does not question that streetlights are needed for safety. The astronomer addresses the conclusion believed by others, not their premises.
C
proposing an alternative scientific explanation for a natural phenomenon
The astronomer does not propose an alternative explanation for light interference.
D
making a distinction between terms
The astronomer does not distinguish any terms.
E
offering a counterexample to a general claim
The general claim is other people’s argument that interference from light is inevitable. The counterexample the astronomer offers is the city of Sandsville, which does not experience light interference.
A
denies that an observation that a trait is common to all the events in a pattern can contribute to a causal explanation of the pattern
The trait (A) is referencing is self-interest and the pattern is human action, but the author doesn’t say that self-interest can’t contribute to a causal explanation of human action. On the contrary, the author argues that self-interest is the main influence on human action.
B
takes the occurrence of one particular influence on a pattern or class of events as showing that its influence outweighs any other influence on those events
The author argues that simply because self-interest influences motives that influence all human actions, self-interest outweighs any other influences on human actions. The author errs by never addressing how self-interest is the main influence on human actions.
C
concludes that a characteristic of a pattern or class of events at one time is characteristic of similar patterns or classes of events at all times
The author never argues that self-interest influences human actions at some times and, therefore, influences similar patterns or classes of events at all times. He only argues that self-interest is the principal influence on human actions.
D
concludes that, because an influence is the paramount influence on a particular pattern or class of events, that influence is the only influence on that pattern or class of events
The author doesn’t make the case that self-interest is the only influence on human action. He just argues that self-interest is the chief influence on human action.
E
undermines its own premise that a particular attribute is present in all instances of a certain pattern or class of events
The author’s only premise is that motives that influence all human actions come from self-interest. He never undermines this premise.
Summarize Argument: Phenomenon-Hypothesis
The agricultural official presents the hypothesis that a new pesticide is more effective than the old pesticide at protecting pears against insects, at least over a short-term period. This hypothesis is based on observing that when pear farmers in District 10 switched from the old pesticide to the new pesticide for 3 years, they lost fewer pears to insects than during the previous 3 years.
Notable Assumptions
The agricultural official assumes that just because there were fewer pears lost to insects while the new pesticide was in use, the new pesticide was the cause of this change. In other words, the official assumes that there wasn’t some other factor which could have been the true cause of the farmers’ results.
A
The amount of fruit that an orchard can potentially produce depends in part on how many mature trees it contains, and the number of mature pear trees in District 10 has declined steadily over the past eight years.
This does not weaken, and so is the correct answer. This claim doesn’t explain why there would be fewer pears lost to insects in the last 3 years. Overall pear production can change without affecting the proportion of pears that insects destroy, so this just gives us nothing.
B
During the past five years, the farmers of the District 10 Farmers’ Cooperative have been gradually implementing a variety of insect-abatement programs, and some of these programs have proven successful.
This weakens the argument by providing an alternative explanation for the observation. If the pear farmers have been gradually implementing anti-insect programs, then it makes sense that the last 3 years would see fewer insect losses.
C
Over the past five years, one of the several species of birds that typically prey on the insects that feed on pears has gradually shifted its migratory patterns, spending more and more months each year in the region that contains District 10.
This weakens the argument by providing an alternative explanation for the observation. If insect-eating birds have been spending more time around District 10, they would have eaten more insects, thus protecting the pears.
D
Some of the species of insects in District 10 that infest pear trees are water breeders, and the reservoirs and marshlands in this district have been shrinking rapidly over the past three years.
This weakens the argument by providing an alternative explanation for the observation. If pear-eating insects have had less water in which to breed, then there would be fewer insects, which explains why there have been fewer pears eaten by insects.
E
The effects of certain pesticides, including the pesticide that had formerly been used in District 10, are cumulative and persist for several years after the pesticide is no longer applied.
This weakens the argument by providing an alternative explanation for the observation. If the effects of the old pesticide get stronger with each use and last for years, then the pears would have been protected by a strong built-up effect during the 3 years in question.
Summarize Argument
The newsletter concludes that volunteering can benefit one’s well-being. It supports this by noting that retired people who volunteer tend to show fewer signs of aging than retired people who don’t, and that volunteers are stronger socially, mentally, physically, and economically than non-volunteers.
Identify and Describe Flaw
This is a cookie-cutter “correlation does not imply causation” flaw, where the newsletter sees a positive correlation and then jumps to the conclusion that one thing causes the other, without ruling out alternative hypotheses. Specifically, it overlooks two key alternatives:
(1) The causal relationship could be reversed— maybe stronger people tend to volunteer more, not the other way around.
(2) Some other, underlying factor could be causing the correlation—maybe there’s something that causes people to both be stronger and to volunteer.
A
the center has a self-interested motive to attract new volunteers
This might be true; we don’t have enough information to know either way. But even if it is true, (A) doesn't describe the logical flaw in the newsletter’s argument. It’s based on that logical flaw that “the inference drawn above is unwarranted.”
B
it interprets “well-being” as including the factors of social and economic resources, mental outlook, physical health, and overall functioning
This is true, but it doesn’t describe the flaw in the newsletter’s argument. Interpreting “well-being” in this way is entirely reasonable.
C
some of those who do not volunteer might be older than some volunteers and so could not be considered their peers
This is true, but it doesn’t describe the flaw in the newsletter’s argument. Some of those who don’t volunteer might also be younger than some volunteers; it doesn’t matter to the argument, which only compares retired volunteers with their “nonvolunteering contemporaries.”
D
growing older might not necessarily result in a change in mental outlook
This might be true, but it doesn't describe the flaw in the newsletter’s argument. The argument assumes that volunteering causes a stronger mental outlook. It doesn’t assume that growing older causes a change in mental outlook.
E
those with better resources, health, outlook, and functioning are more able to work as volunteers
This describes an alternative hypothesis that the author ignores. She assumes that volunteering causes increased well-being, without considering that instead, those with a higher well-being might be more likely or more able to volunteer.