Summarize Argument: Counter-Position
Dobson concludes that the people who built the ring of stones in Britain were not knowledgeable about celestial events. He supports this by saying that, because there are many stones in the ring, there’s a good chance that one pair of stones would point in a celestially significant direction.
Identify and Describe Flaw
This is the cookie-cutter flaw of confusing a rejection of someone’s argument with a rejection of their conclusion. Dobson concludes that the historians’ conclusion is false, simply because their evidence doesn’t establish their conclusion. But just because someone’s evidence is insufficient doesn’t mean you can assume that the opposite of their conclusion is true.
A
The failure of cited evidence to establish a statement is taken as evidence that that statement is false.
Dobson concludes that the people who built the stone ring didn’t understand celestial events, just because the historians’ evidence fails to establish their conclusion. But a lack of evidence doesn’t mean you can automatically assume the opposite of someone’s conclusion.
B
Dobson’s conclusion logically contradicts some of the evidence presented in support of it.
This is the cookie-cutter flaw of internal contradiction. Dobson doesn’t make this mistake. His argument is flawed, but it isn’t contradictory.
C
Statements that absolutely establish Dobson’s conclusion are treated as if they merely give some support to that conclusion.
Actually, Dobson treats his evidence as if it absolutely establishes his conclusion, even though it doesn’t establish it at all.
D
Something that is merely a matter of opinion is treated as if it were subject to verification as a matter of fact.
The builders of the ring were either knowledgeable about celestial events or they were not; this isn’t a matter of opinion. It may be Dobson’s opinion that there’s a high chance that a pair of stones would point to something significant, but this isn’t the flaw in his argument.
E
Dobson’s drawing the conclusion relies on interpreting a key term in two different ways.
This is the cookie-cutter flaw of equivocation. Dobson never makes this mistake in his argument.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that owning a laptop leads to a higher-paying job. As evidence, he cites an economist who found that, among people who used computers at work last year, those who owned laptops earned 25% more on average than those who didn’t.
Identify and Describe Flaw
This is a cookie-cutter “correlation does not imply causation” flaw, where the author sees a positive correlation and jumps to the conclusion that one thing causes the other, without ruling out alternative hypotheses. Specifically, he overlooks two key alternatives:
(1) The causal relationship could be reversed—maybe having a higher-paying job allows people to own laptops, not the other way around.
(2) Some other, underlying factor could be causing the correlation—maybe there’s something that causes people to both have higher-paying jobs and own laptops.
A
It attempts to support a sweeping generalization on the basis of information about only a small number of individuals.
The conclusion is a fairly broad generalization. However, we have no idea how big the economist’s sample was and we can’t assume that he only studied “a small number of individuals.”
B
Its conclusion merely restates a claim made earlier in the argument.
This is the cookie-cutter flaw of circular reasoning, where one’s conclusion simply restates a premise. But the author doesn't make this mistake; instead, he confuses correlation for causation.
C
It concludes that one thing was caused by another although the evidence given is consistent with the first thing’s having caused the second.
This is a cookie-cutter “correlation does not imply causation” flaw. The author concludes that owning a laptop causes people to have a higher-paying job, even though it’s more likely that having a higher-paying job causes people to be able to own a laptop.
D
It offers information as support for a conclusion when that information actually shows that the conclusion is false.
The author’s argument simply doesn’t contradict itself in this way. His evidence may not show that his conclusion is true, but it also doesn’t show that his conclusion is false.
E
It uncritically projects currently existing trends indefinitely into the future.
The author makes a causal conclusion about something that happened last year. He doesn’t make a predictive conclusion about what will happen indefinitely into the future.
Mature white pines intercept almost all the sunlight that shines on them. They leave a deep litter that dries readily, and they grow to prodigious height so that, even when there are large gaps in a stand of such trees, little light reaches the forest floor. For this reason white pines cannot regenerate in their own shade. Thus, when in a dense forest a stand of trees consists of nothing but mature white pines, it is a fair bet that _______.
Summary
Mature white pines intercept almost all the sunlight they receive. They leave a deep litter and grow tall enough so that little light reaches the forest floor even with little gaps between trees. White pines cannot regenerate in their own shade.
Strongly Supported Conclusions
In a forest of mature white pines, it is unlikely that any adjacent pines differ widely in age.
A
the ages of the trees in the stand do not differ from each other by much more than the length of time it takes a white pine to grow to maturity
This is strongly supported because we know that mature white pines next to each other leave so little sunlight on the forest floor that white pines cannot regenerate. This would prevent young trees from emerging where pines are already mature.
B
the land on which the stand is now growing had been cleared of all trees at the time when the first of the white pines started growing
This is unsupported because it is not required that all white pines are cleared for new ones to grow. The stimulus only tells us that stands of mature white pines prevent regeneration.
C
competition among the trees in the stand for sunlight will soon result in some trees’ dying and the stand thus becoming thinner
This is unsupported because even though the competition for sunlight may prevent new white pines from growing between mature trees, we have no reason to suspect that already mature trees will compete with each other for sunlight.
D
other species of trees will soon begin to colonize the stand, eventually replacing all of the white pines
This is unsupported because the stimulus provides no information on other trees outcompeting stands of mature white pines.
E
any differences in the heights of the trees in the stand are attributable solely to differences in the ages of the trees
This is unsupported because we don’t know that there aren’t other factors like rain or nutrition that contribute to height differences.
Art critic: But in a copy of Veronese’s painting made shortly after Veronese died, the cloak is red. It is highly unlikely that a copyist would have made so major a change so soon after Veronese’s death.
Summarize Argument
The curator argues that the decision to restore part of a painting to its original green, rather than the current red, is justified. The curator supports this claim by asserting that another artist probably added the red to the painting. This assertion is a sub-conclusion, because it is further supported by the factual premise that the red paint was a late addition to the painting, and wasn’t from the original artist’s workshop.
Identify Argument Part
The assertion that a later artist tampered with Veronese’s painting is a sub-conclusion in the curator’s argument. It is supported by evidence from x-ray and chemical tests, and in turn supports the conclusion that restoring the original green colour in the painting is justified.
A
It is the main point toward which the argument as a whole is directed.
The claim about another artist tampering with the painting supports the further conclusion that restoring the painting is justified, so it can’t be the main conclusion itself.
B
It is a subsidiary conclusion that supports the argument’s main conclusion.
This correctly characterizes the assertion that another artist tampered with the painting. That assertion is supported by factual evidence, but also supports the main conclusion: the whole reason restoration is justified is because the red wasn’t the original artist’s choice.
C
It is a clarification of a key term of the argument.
The claim about tampering doesn’t clarify any kind of terminology. In fact, no part of the argument focuses on clarifying terminology.
D
It is a particular instance of the general position to be defended.
The argument doesn’t state any general position to be defended. The curator’s entire focus is on one specific case, and there’s no general principle stated in the argument.
E
It is a reiteration of the main point that is made for the sake of emphasis.
The claim about tampering is not a restatement, nor is it restated. The curator never repeats a claim, including the true main point that the restoration is justified.
Summarize Argument
The author concludes that it’s safer for dogs to get the vaccine than to skip it. She supports this by saying that the vaccine is almost 100% effective at preventing the disease. Also, the risk of death from the vaccine is 1 in 5,000, whereas 1 in 50 dogs who get the disease die.
Notable Assumptions
For the vaccine to be more beneficial than costly, the author must assume that the disease is fairly common. While 1 in 5,000 vaccinated dogs die, and 1 in 50 dogs who get the disease die, we don’t know how many dogs will actually get the disease in the first place.
She also assumes that her argument applies to any dog, without considering how the disease or vaccine might affect different breeds or dogs differently.
She also overlooks any unaddressed costs of getting the vaccine, or any unaddressed costs or benefits of not getting it.
A
the total number of dogs that die each year from all causes taken together
Irrelevant— the author only addresses deaths from this particular disease and vaccination. The number of dogs that die each year from everything else is not relevant to her argument.
B
whether the vaccine is effective against the disease in household pets other than dogs
Irrelevant— the author is only discussing the effectiveness of the vaccine among dogs. How other animals might be affected by the disease or the vaccine doesn’t matter here.
C
the number of dogs that die each year from diseases other than the disease in question
Irrelevant— like (D), the author is only concerned with the number of dogs that die each year from the particular disease in question. She doesn’t address the dangers or mortality rates of any other diseases.
D
the likelihood that a dog will contract another disease such as rabies
Irrelevant— like (C), the author’s argument only addresses the disease in question. It doesn’t matter how likely a dog might be to contract some other kind of disease.
E
the likelihood that an unvaccinated dog will contract the disease in question
If the likelihood of catching the disease is high, getting the vaccine may indeed be more beneficial, since the risk of death from the vaccine is much lower than from the disease. But if the likelihood is low, the added risk of vaccination might be more costly overall.