Some biologists believe that the capacity for flight first developed in marine reptiles, claiming that feathers are clearly developed from scales. Other biologists rightly reject this suggestion, pointing out that bats have no scales and that nonmarine reptiles also have scales. Those who believe that flight first developed in tree-dwelling reptiles reject the claim that the limbs of land-dwelling reptiles might have developed into wings. They insist that it is more likely that tree-dwelling reptiles developed wings to assist their leaps from branch to branch.

Summarize Argument: Counter-Position
The author’s conclusion rejects the view of biologists who believe that the capacity for flight first developed in marine reptiles. Those biologists, with whom the author disagrees, support their claim with the theory that feathers developed from scales. To support his rejection of these biologists, the author uses the example of bats, which fly and have no scales, and non-marine reptiles that have scales. These examples cast doubt on the view that marine reptiles first developed the capacity for flight.
In the last two sentences of the stimulus, the author actually introduces a completely new argument! The discussion in the last two sentences is not relevant for our understanding of the author’s perspective.

Identify Argument Part
The claim in the question stem supports the author’s rejection of the view that flight first developed in marine reptiles.

A
It is cited as evidence against the claim that the capacity for flight first developed in marine reptiles.
The claim in the question stem is a premise that supports the author’s conclusion, which is that it is not true that the capacity for flight first developed in marine reptiles. (A) encapsulates this.
B
It is cited as evidence against the claim that the capacity for flight first developed in land-dwelling animals.
The second (irrelevant) argument makes a claim that it is less likely that land-dwelling reptiles’ limbs developed into wings. (B) includes an imprecise reference to this second argument; the claim in the question stem has no relationship with this second argument.
C
It is cited as evidence against the claim that the capacity for flight first developed in tree-dwelling reptiles.
The claim in the question stem does has no relationship to the claim that flight first developed in tree-dwelling animals; instead, the claim in the question stem is used to reject the claim about flight and marine animals.
D
It weakens the claim that tree-dwelling reptiles were the first kind of reptile to develop the capacity for flight.
The claim in the question stem has no relationship to the claim that flight first developed in tree-dwelling animals; instead, the claim in the question stem is used to reject the claim about flight and marine animals.
E
It corroborates the observation that some mammals without scales, such as bats, developed the capacity to fly.
The claim in the question stem works together with the observation that some mammals without scales can fly; these two claims don’t support each other, but they work together to support the main conclusion.

18 comments

A year ago the government reduced the highway speed limit, and in the year since, there have been significantly fewer highway fatalities than there were in the previous year. Therefore, speed limit reduction can reduce traffic fatalities.

Summarize Argument: Phenomenon-Hypothesis

The author concludes that a speed limit reduction can reduce traffic fatalities. This is based on the fact that a year ago, the government reduced the highway speed limit, and in the year since that reduction, there have been fewer highway deaths than there were in the previous year.

Identify and Describe Flaw

The author assumes that the reduction in highway speed limit caused the decrease in highway fatalities. This overlooks the possibility that there are other explanations for the decrease in highway fatalities in the year following the speed limit reduction.

A
highway traffic has not increased over the past year

The negation of (A) doesn’t undermine the argument. If traffic has increased over the past year, that might strengthen the argument, because we’d expect to see more fatalities. Since the negation doesn’t hurt the argument, the author doesn’t have to assume (A).

B
the majority of drivers obeyed the new speed limit

The author doesn’t have to assume that most drivers obeyed the speed limit, because a speed limit reduction can still affect driving behavior even if most people don’t follow the speed limit. For example, the new limit can cause people to drive slower.

C
there is a relation between driving speed and the number of automobile accidents

The author’s conclusion concerns the number of highway deaths. This doesn’t commit the author to any belief about the number of accidents, which is different from the number of deaths.

D
the new speed limit was more strictly enforced than the old

If anything, the author assumes that the new speed limit was not more strictly enforced. More strict enforcement could have been an alternate explanation for the decline in fatalities. So the author assumes this didn’t happen, not that it did happen.

E
the number of traffic fatalities the year before the new speed limit was introduced was not abnormally high

This must be assumed because if the number of fatalities the year before the new limit was abnormally high, then that suggests the decrease in fatalities after the speed limit might just be a coincidence. It might be a return to the normal fatality rate.


108 comments

As part of a survey, approximately 10,000 randomly selected individuals were telephoned and asked a number of questions about their income and savings. Those conducting the survey observed that the older the person being queried, the more likely it was that he or she would refuse to answer any of the questions. This finding clearly demonstrates that, in general, people are more willing when they are younger than when they are older to reveal personal financial information to strangers over the telephone.

Summarize Argument: Phenomenon-Hypothesis
The argument concludes that people become more unwilling to discuss personal finances with strangers over the phone throughout their lifetime. The author bases his conclusion on a survey that found that older people are more unwilling to discuss their personal finances with a surveyor over the phone than younger people are.

Identify and Describe Flaw
Our argument uses survey results about different generations of people to support a claim about how people change as they age. This conclusion doesn’t follow; if you want to make a claim about how people’s behaviors change throughout their lives, you should interview the same people at different points in their lives. All that the survey results tell us is how different generations differ behaviorally, not how one generation will change in the future.

A
offers no evidence that the individuals queried would have responded differently had they been asked the same questions in years prior to the survey
This addresses the issue of change over time. If we don’t know how the answers of the people surveyed would change over time, we cannot draw the conclusion about how anyone’s behavior from earlier in their life to later.
B
fails to specify the exact number of people who were telephoned as part of the survey
Knowing the exact number of people telephoned does not help our argument—it would not help us establish a connection between the older and younger people surveyed and how people change throughout their lives.
C
assumes without warrant that age is the main determinant of personal income and savings levels
Even if it were untrue that age was the main determinant of these factors, that would not damage the argument. Our argument is not focused on the level of income or savings, but rather on how forthcoming people of certain ages are with this information.
D
assumes from the outset what it purports to establish on the basis of a body of statistical evidence
This “cookie-cutter” answer choice refers to circular reasoning, which is not present in this argument. The study would have had to assume that people become less likely to share this information as they age. Since this was not the case, we can reject this answer choice.
E
provides no reason to believe that what is true of a given age group in general is also true of all individuals within that age group
Our argument is concerned with the difference between different age groups and how people change throughout their lives, not with whether or not generalizations are universally true within a group. This answer choice misses the mark.

37 comments

Social critic: The whole debate over the legal right of rock singers to utter violent lyrics misses the point. Legally, there is very little that may not be said. But not everything that may legally be said, ought to be said. Granted, violence predates the rise in popularity of such music. Yet words also have the power to change the way we see and the way we act.

Summary

The debate over the legal right of rock singers to say violent lyrics misses the point. There is legally very little that cannot be said. Not everything that can legally be said ought to be said. Violence came before the popularity of violent lyrics in music. Words can change how we see and how we act.

Strongly Supported Conclusions

There could be a relationship between violent song lyrics and violent views and actions.

A
If rock music that contains violent lyrics is morally wrong, then it should be illegal.

This is anti-supported because the author states that very little speech is illegal and that there is a difference between things that are legal and things that ought to be said. The author doesn’t advocate making any speech illegal.

B
The law should be changed so that the government is mandated to censor rock music that contains violent lyrics.

This is unsupported because the author does not advocate for a change in laws, and the author draws a distinction between what can be said legally versus what ought to be said.

C
Violent rock song lyrics do not incite violence, they merely reflect the violence in society.

This is anti-supported because the author states that words can influence how we act, meaning the author thinks it is possible for violent lyrics to lead to some violent acts.

D
If rock musicians voluntarily censor their violent lyrics, this may help to reduce violence in society.

This is strongly supported because the author states that words, exemplified by violent lyrics, can affect how people act. This means that choosing not to speak violent lyrics could reduce violent acts.

E
Stopping the production of rock music that contains violent lyrics would eliminate much of the violence within society.

This is unsupported because the author concedes that violent acts predate violent lyrics. While the author thinks there is a connection between words and actions, it is unclear that stopping these lyrics would eliminate “much” violence.


61 comments

A plausible explanation of the disappearance of the dinosaurs is what is known as the comet theory. A large enough comet colliding with Earth could have caused a cloud of dust that enshrouded the planet and cooled the climate long enough to result in the dinosaurs’ demise.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the comet theory is a plausible explanation of the dinosaurs’ extinction. This is based on the idea that a collision of a large enough comet into the Earth could have caused a dust cloud that could have cooled the climate long enough to cause the extinction of the dinosaurs.

Notable Assumptions
The author assumes that a large enough comet existed and could have collided with Earth at the time in question. He also assumes that the impact would cause a dust cloud that would cover the planet, and that this would cool the climate long enough to lead to the dinosaurs’ extinction. (The author says that these events “could” happen––we don’t know their likelihood. It could be a very slim possibility.) The author assumes that, even if these events occurred, the cooling caused by the comet is what led to the dinosaurs’ extinction.

A
One of the various schools of paleontology adheres to an explanation for the disappearance of the dinosaurs that is significantly different from the comet theory.
The author is only arguing that the comet theory is plausible; the fact that other theories differ from the comet theory doesn’t weaken the argument. It doesn’t weaken our argument that other plausible explanations may exist.
B
Various species of animals from the same era as the dinosaurs and similar to them in physiology and habitat did not become extinct when the dinosaurs did.
(B) suggests that the extinction of the dinosaurs was driven by some factor that differentiated dinosaurs from other animals with similar habitat and climate needs. If the comet theory was true, animals with similar physiology and habitat to dinosaurs would have gone extinct too.
C
It cannot be determined from a study of dinosaur skeletons whether the animals died from the effects of a dust cloud.
(C) just says that one specific kind of evidence cannot be used. The inability to use skeletons as evidence does not weaken the argument that the comet theory is plausible. (C) makes the inappropriate assumption that skeletons are the only source of information available.
D
Many other animal species from the era of the dinosaurs did not become extinct at the same time the dinosaurs did.
(D) is too broad. The animal species referenced in (D) could have had vastly different requirements for habitat and climate. It makes sense that some animals survived the incident that killed the dinosaurs.
E
The consequences for vegetation and animals of a comet colliding with Earth are not fully understood.
The argument that the comet theory is plausible doesn’t require a full understanding of the impacts of a comet collision on plants and animals, so (E) does not impact the argument.

27 comments

The desire for praise is the desire to obtain, as a sign that one is good, the favorable opinions of others. But because people merit praise only for those actions motivated by a desire to help others, it follows that one who aids others primarily out of a desire for praise does not deserve praise for that aid.

Summary
The author concludes that people who help others mainly out of a desire for praise do not deserve praise for that help. This is based on the following:
The desire for praise is the desire to obtain the favorable opinions of others.
If someone deserves praise for an action (”merit” = “deserve”), that action must be motivated by a desire to help others.

Missing Connection
We’re trying to prove that people who help others mainly out of a desire for praise don’t deserve praise for that help. We know from the second premise that in order to deserve praise, the action must be motivated by a desire to help others. So if we can show that people who help others mainly out of a desire for praise are NOT motivated by a desire to help others, that would prove our conclusion.

A
An action that is motivated by a desire for the favorable opinion of others cannot also be motivated by a desire to help others.
The first premise establishes that the desire for praise is the desire to obtain the favorable opinions of others. (A) would establish that helping others mainly out of the desire for praise constitutes an action that is NOT motivated by a desire to help others. This then would connect with the second premise, which takes us to “not deserve praise.”
B
No action is worthy of praise if it is motivated solely by a desire for praise.
The conclusion concerns people who help others “primarily” out of a desire for praise. (B), which tells us that actions motivated “solely” by praise don’t deserve praise, doesn’t cover actions that are done “primarily” out of desire for praise.
C
People who are indifferent to the welfare of others do not deserve praise.
We don’t know that people who help others primarily out of a desire for praise are indifferent to the welfare of others. Maybe they do care about others...it’s just that their action is mainly about getting praise.
D
One deserves praise for advancing one’s own interests only if one also advances the interests of others.
It’s not clear that one who helps others out of a desire for praise is actually advancing their own interests. It’s also not clear that helping others out of a desire for praise wouldn’t advance the interests of others. So (D) doesn’t connect to any of the premises of this argument.
E
It is the motives rather than the consequences of one’s actions that determine whether one deserves praise for them.
(E) establishes that motives determine whether one deserve praise. But (E) allows for actions out of selfish motives, such as desire for praise, to still deserve praise. (E) doesn’t tell us what kind of motive would make an action undeserving of praise.

41 comments

Rosen: One cannot prepare a good meal from bad food, produce good food from bad soil, maintain good soil without good farming, or have good farming without a culture that places value on the proper maintenance of all its natural resources so that needed supplies are always available.

Summary

Good meal → NOT bad food

Good food → NOT bad soil

Good soil → Good farming

Good farming → culture that places value on maintaining natural resources

Very Strongly Supported Conclusions

Normally, I wouldn’t think “NOT bad food” implies “good food,” since there might be something that’s just not bad and not good — just middle-of-the-road food. Same thing with “NOT bad soil” and “good soil.”

But, the stimulus seems to be set up in order for us to draw a conditional chain connecting every statement.

Good meal → good food → good soil → good farming → culture that places value on maintining natural resources.

I know this seems inappropriate, but consider this problem unusual, and don’t draw too many lessons from it. Think of this problem as an exception.

A
The creation of good meals depends on both natural and cultural conditions.

Supported, if we accept the conditional chain starting with “good meal” and ending with “culture that maintains natural resources.” A good meal depends on natural conditions, such as soil. And it depends on cultural conditions, such as a culture’s view of natural resources.

B
Natural resources cannot be maintained properly without good farming practices.

We know good farming is necessary for good soil. But there’s no support for the claim that good farming is necessary for maintaining natural resources. There are many other kinds of natural resources besides soil, and we don’t know whether good farming is related to those other resources.

C
Good soil is a prerequisite of good farming.

We know good farming is necessary for good soil. But this doesn’t mean good soil is necessary (prerequisite) for good farming.

D
Any society with good cultural values will have a good cuisine.

We don’t know anything about good “cuisine.” A cuisine is different from a meal. We also don’t know that “good cultural values” is sufficient for anything.

E
When food is bad, it is because of poor soil and, ultimately, bad farming practices.

Food might be bad for other reasons besides poor soil and bad farming. We know that good food requires good soil and good farming, but it might also require other things. So we might have good soil and good farming, but still end up with bad food.


99 comments