Summary
The author concludes that there is no consistent causal link between major meteor impacts and mass extinctions. This is the based on the following:
Many extinctions didn’t follow major meteor impacts.
Many major meteor impacts were not followed by mass extinctions.
Many extinctions didn’t follow major meteor impacts.
Many major meteor impacts were not followed by mass extinctions.
Missing Connection
The premises don’t establish what implies that there’s “no consistent causal link” between major meteor impacts and mass extinctions. Although we know that many extinctions didn’t follow such impacts, and that many impacts weren’t followed by such extinctions, how do we know that this isn’t a consistent causal link?
We want to establish that if many extinctions didn’t follow major meteor impacts or if many major meteor impacts were not followed by mass extinctions, then this proves there’s no consistent causal link between such impacts and such extinctions.
We want to establish that if many extinctions didn’t follow major meteor impacts or if many major meteor impacts were not followed by mass extinctions, then this proves there’s no consistent causal link between such impacts and such extinctions.
A
If there were a consistent causal link between major meteor impacts and mass extinctions, then all major meteor impacts would be followed by mass extinctions.
(A) establishes that in order for there to be a consistent causal link between the impacts and mass extinctions, then ALL major meteor impacts would be followed by such extinctions. We know from one of our premises that many major meteor impacts were NOT followed by such extinctions. This triggers the contrapositive of (A), which would establish that there is NO consistent causal link.
B
Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.
(B) establishes that in order for there to be a consistent causal link, it’s required that many mass extinctions have followed major meteor impacts. But we don’t know that this requirement hasn’t been met. Although we do know that many mass extinctions have followed major meteor impacts, it’s still possible that many such extinctions have followed such impacts.
C
Of the mass extinctions that did not follow any known major meteor impacts, few if any followed major meteor impacts of which the geological record contains no hints.
(C) doesn’t establish what is required for a “consistent causal link” between extinctions and meteor impacts, so it can’t make the argument valid.
D
If there is no consistent causal link between major meteor impacts and mass extinctions, then not all mass extinctions could have followed major meteor impacts.
(D) establishes what would be true IF there is no consistent causal link. But we’re trying to reach the conclusion that there is no consistent causal link. We don’t want “no consistent causal link” to appear in the “IF” part of an “If, then” answer. We want it to appear in the “then” part.
E
There could be a consistent causal link between major meteor impacts and mass extinctions even if not every major meteor impact has been followed by a mass extinction.
(E) tells us about one circumstance under which there can be a consistent causal link. But we’re trying to prove that there’s NO consistent causal link.
Summarize Argument: Phenomenon-Hypothesis
The author concludes that dioxin released from paper mills is unlikely to be the cause of reproductive abnormalities in fish immediately downstream of the mills. This is because when the mills shut down, the fish recover normal hormone concentrations relatively quickly, even though dioxin decomposes very slowly in the environment (which suggests the dioxin didn’t just disappear quickly from the area).
Notable Assumptions
The author assumes that the dioxin is still present around the fish immediately downstream of the paper mill during the mill shutdowns. This is why the author thinks the quick recovery of the fish shows that dioxin isn’t likely to be the cause of the fish’s problems. The author also assumes that the reproductive abnormalities in the fish are caused by abnormal hormone concentrations.
A
Some of the studies that show that fish recover quickly during shutdowns were funded by paper manufacturers.
Whoever funded the studies doesn’t change anything about what the studies found. We have no reason to think the source of funding affected how the study was done in a way that would lead us to question the results.
B
The rate at which dioxin decomposes varies depending on the conditions to which it is exposed.
A premise already establishes that dioxin decomposes very slowly in the environment. Although the rate might not be exactly the same in all environments, we still know it decomposes very slowly. So, (B) doesn’t suggest that the dioxin might have decomposed quickly.
C
Normal river currents carry the dioxin present in the river far downstream in a few hours.
This shows dioxin might not be around the fish anymore during a shutdown. This is why the recovery of the fish during a shutdown does not constitute strong evidence that dioxin isn’t the cause. If dioxin isn’t around the fish at these times, that might be the reason fish recover.
D
Some of the fish did not recover rapidly from the physiological changes that were induced by the changes in hormone concentrations.
One assumption is that the reproductive abnormalities are caused by hormone concentrations. Even if we interpret “physiological changes” as including reproductive abnormalities (which is not clear), this affirms a link between hormones and reproductive abnormalities.
E
The connection between hormone concentrations and reproductive abnormalities is not thoroughly understood.
The fact the connection is not thoroughly understood does not undermine the assumption that hormone concentrations cause reproductive abnormalities. The issue is not how well we understand the relationship; it’s about whether there exists a causal relationship.
Summary
The author concludes that moderate exercise lowers the risk of blockage of arteries due to blood clots. This is based on the following:
If it lowers blood cholesterol levels, it lowers the risk of arterial blockage due to blood clots.
If the data reported in a recent study are correct, moderate exercise lowers blood cholesterol levels.
If it lowers blood cholesterol levels, it lowers the risk of arterial blockage due to blood clots.
If the data reported in a recent study are correct, moderate exercise lowers blood cholesterol levels.
Missing Connection
To prove that moderate exercise lowers the risk of blockage of arteries due to blood clots, we want to know that moderate exercise lowers blood cholesteral levels. There is a way to prove that — if the data reported in a recent study are correct, then moderate exercise lowers blood cholesterol levels. But do we know whether the data reported in the recent study is correct? No — that’s what’s missing. We want to know that the data is correct.
A
The recent study investigated the relationship between exercise and blood cholesterol levels.
We want to know that the data reported in the recent study is correct. Whether the study investigated the relationship between exercise and blood cholesterol levels doesn’t tell us anything about whether the data is correct.
B
Blockage of the arteries due to blood clots can be prevented.
The argument concerns lowering the risk of blockage of arteries due to blood clots. Whether such blockage can be completely prevented is a separate issue from whether the risk of such blockage can be decreased. In any case, we’re looking for an answer that establishes the data in the study is correct, and (B) doesn’t establish this.
C
Lowering blood cholesterol levels lowers the risk of blockage of the arteries.
This is supported by the premises, but it’s not new information that makes the argument valid. We want to know that the data reported in the study is correct, so that we can establish that moderate exercise lowers blood cholesterol. (C) doesn’t tell us anything about the data.
D
The data reported in the recent study are correct.
(D) allows us to infer that moderate exercise lowers blood cholesterol levels. This inference, combined with the premise establishing that anything that lowers blood cholesterol levels lowers risk of arterial blockage due to blood clots, establishes that moderate exercise lowers such risk of blockage.
E
Hardening of the arteries increases the risk of blockage of the arteries due to blood clots.
This may be supported by the premises, but it’s not new information that makes the argument valid. We want to know that the data reported in the study is correct, so that we can establish that moderate exercise lowers blood cholesterol. (E) doesn’t do this.
Summarize Argument
The author concludes that Cotrell can only write average quality magazine articles. She supports this by saying that any superior articles by Cotrell must be plagiarized, because Cotrell can only write average quality articles.
Identify and Describe Flaw
This is the cookie-cutter flaw of circular reasoning, where the author’s conclusion is simply a restatement of a premise. In this case, the author concludes that Cotrell can only write average quality articles based on the premise that his superior articles must be plagiarized because he can only write average quality articles.
A
It simply ignores the existence of potential counterevidence.
The author actually discusses potential counterevidence: Cotrell’s few superior articles. She dismisses this evidence by saying that the articles must have been plagiarized, but she doesn’t ignore the existence of counterevidence.
B
It generalizes from atypical occurrences.
The author doesn’t generalize from atypical occurrences. Instead, she draws a specific conclusion about Cotrell based on all of Cotrell’s articles— the superior ones and the average ones.
C
It presupposes what it seeks to establish.
The author seeks to establish that Cotrell can only write average quality articles. In order to do so, she presupposes that he can only write average quality articles.
D
It relies on the judgment of experts in a matter to which their expertise is irrelevant.
The author never mentions or relies on the judgement of any experts.
E
It infers limits on ability from a few isolated lapses in performance.
The author does infer limits on Cotrell’s writing ability. But she does so based on his average work and the claim that his superior work was plagiarized, not based on “a few isolated lapses in performance.”
Summarize Argument
The author concludes that it’s likely Tom is an extreme insomniac. This is based on the fact that 90 percent of extreme insomniacs drink lots of coffee, and Tom drinks lots of coffee.
Identify and Describe Flaw
The author misinterprets the claim “Most A are B” as “Most B are A.” Although 90 percent of extreme insomniacs drink lots of coffee, that doesn’t tell us anything about what proportion of lots-of-coffee drinkers are extreme insomniacs. It could be that the vast majority of lots-of-coffee drinkers aren’t extreme insomniacs, even if most extreme insomniacs drink lots of coffee.
A
It fails to acknowledge the possibility that Tom is among the 10 percent of people who drink large amounts of coffee who are not extreme insomniacs.
The premises don’t establish that only 10 percent of people who drink lots of coffee are not extreme insomniacs. Also, the conclusion doesn’t say that Tom definitely is an extreme insomniac. So, the author acknowledges that he might not be an extreme insomniac.
B
It fails to consider the possible contribution to extreme insomnia of other causes of insomnia besides coffee.
The author’s argument does not make any assumptions about cause. The issue is whether membership in the set of people who drink lots of coffee implies a likelihood of membership in the set of people who are extreme insomniacs.
C
It relies on evidence that does not indicate the frequency of extreme insomnia among people who drink large amounts of coffee.
The author relies on the fact that 90% of extreme insomniacs drink lots of coffee. This does not reveal the frequency (i.e. proportion) of extreme insomnia among people who drink lots of coffee. It could be that only a small % of lots-of-coffee drinkers have extreme insomnia.
D
It draws an inference about one specific individual from evidence that describes only the characteristics of a class of individuals.
The author does not commit the whole-to-part fallacy. The issue is misinterpretation of the claim “90% of extreme insomniacs consume lots of coffee.” This statistic is not a claim about a class — it’s a claim about 90% of the individuals within the class.
E
It presumes without warrant that drinking coffee always causes insomnia.
The author doesn’t make any assumptions about cause. The issue is whether membership in the set of people who drink lots of coffee implies a likelihood of membership in the set of people who are extreme insomniacs.