Early urban societies could not have been maintained without large-scale farming nearby. This is because other methods of food acquisition, such as foraging, cannot support populations as dense as urban ones. Large-scale farming requires irrigation, which remained unfeasible in areas far from rivers or lakes until more recent times.

Summary
The stimulus presents several conditional statements that can be connected.
early urban society → large-scale farming
large-scale-farming → irrigation
irrigation → not far from rivers/lakes
Note that the second sentence of the stimulus tells us that other ways of acquiring food besides large-scale-farming can’t support an urban population. But this just repeats the relationship expressed in the first sentence, so it’s not important.

Strongly Supported Conclusions
The three conditionals can be connected to produce the following inference:
early urban society → not far from rivers/lakes
In other words, early urban societies must not have been far from rivers/lakes.

A
Most peoples who lived in early times lived in areas near rivers or lakes.
Unsupported. Even though early urban societies couldn’t be far from rivers/lakes, most people could have lived in rural, non-urban societies far from rivers/lakes.
B
Only if farming is possible in the absence of irrigation can societies be maintained in areas far from rivers or lakes.
Unsupported. The stimulus only tells us about requirements for large-scale farming, not farming generally. Perhaps small-scale farming is possible through irrigation far from water. And we only know about what’s required for early urban societies, not for modern urban societies.
C
In early times it was not possible to maintain urban societies in areas far from rivers or lakes.
Strongly supported. This is the inference we could anticipate from connecting the conditionals in the stimulus. In diagram form it means “far from rivers/lakes → /early urban societies.” This is the contrapositive of the inference described in the summary above.
D
Urban societies with farms near rivers or lakes do not have to rely upon irrigation to meet their farming needs.
Unsupported. We can infer early urban societies had to have large-scale farming, which required irrigation. This doesn’t tell us what kind of society doesn’t require irrigation.
E
Early rural societies relied more on foraging than on agriculture for food.
Unsupported. We know early urban societies required large-scale farming. But early rural societies may have had small-scale farming and may have relied on it more than foraging. The stimulus doesn’t tell us anything about early rural societies.

6 comments

Correction: At 0:22 J.Y. mistakenly says that (E) is the right answer choice. (C) is the actual right answer choice.


47 comments

Philosopher: Graham argues that since a person is truly happy only when doing something, the best life is a life that is full of activity. But we should not be persuaded by Graham’s argument. People sleep, and at least sometimes when sleeping, they are truly happy, even though they are not doing anything.

Summarize Argument: Counter-Position

The philosopher concludes that we should be skeptical of Graham’s argument. Graham starts with the premise that you need to be doing something in order to be truly happy, and uses that premise to conclude that the best life must be full of activity. But the philosopher disagrees with Graham’s premise—she notes that while sleeping, people can be truly happy even through they’re doing nothing.

Identify Argument Part

The claim in the question stem is a premise of the philosopher’s argument. It provides a counterexample to Graham’s only premise by illustrating that “doing something” isn’t actually a requirement for a person to be truly happy. By undermining Graham’s premise, the claim in the question stem in turn casts doubt on Graham’s overall argument.

A
It is a premise of Graham’s argument.

It is a premise of the philosopher’s argument, not Graham’s. It directly contradict’s Graham’s premise.

B
It is an example intended to show that a premise of Graham’s argument is false.

Sleeping is an example of an activity that runs completely counter to Graham’s premise. If, while sleeping, people can be truly happy while doing nothing at all, then Graham’s premise (that people must do something in order to be truly happy) must be false.

C
It is an analogy appealed to by Graham but that the philosopher rejects.

It is the philosopher’s own premise—the philosopher does not reject it. It is also not an analogy; it is a direct example of an activity that runs counter to Graham’s premise.

D
It is an example intended to disprove the conclusion of Graham’s argument.

The philosopher doesn’t go so far as to say that the best life is not a life that is full of activity. In fact, she doesn’t take any position on what the best life entails. She merely calls Graham’s conclusion into question by rejecting his premise.

E
It is the main conclusion of the philosopher’s argument.

It is a premise for the philosopher’s main conclusion. The fact that people can be truly happy while not doing anything undermines Graham’s only premise, which in turns supports the philosopher’s conclusion that we should be skeptical of Graham’s argument.


27 comments

Historian: In rebuttal of my claim that West influenced Stuart, some people point out that West’s work is mentioned only once in Stuart’s diaries. But Stuart’s diaries mention several meetings with West, and Stuart’s close friend, Abella, studied under West. Furthermore, Stuart’s work often uses West’s terminology which, though now commonplace, none of Stuart’s contemporaries used.

Summary

The historian claimed that West influenced Stuart. Other people think West didn’t influence Stuart, because Stuart’s diaries mention West’s work only once. The historian responds to this objection by pointing out that Stuart has a close friend who studied under West, and that Stuart’s diaries mention meetings with West. The historian also points out that Stuart’s work often uses the same terms as West, even though other people working around the same time as Stuart didn’t use those words.

Strongly Supported Conclusions

The fact West’s work was mentioned only once in Stuart’s diaries does not imply that Stuart was not influenced by West.

There’s strong evidence Stuart was influenced by West.

A
Stuart’s discussions with Abella were one of the means by which West influenced Stuart.

Unsupported. There’s no support for the idea that “discussions” were the means by which Stuart was influenced. We don’t even know if Stuart and Abella had discussions. Maybe Stuart was influenced through reading Abella’s work, which could have been influenced by West.

B
It is more likely that Stuart influenced West than that West influenced Stuart.

Unsupported. The stimulus suggests that West influenced Stuart. But it doesn’t say anything concerning whether Stuart influenced West.

C
Stuart’s contemporaries were not influenced by West.

Unsupported. Although the author believes the language Stuart used is evidence of influence by West, that doesn’t suggest people who didn’t use that language weren’t influenced. The contemporaries could have been influenced, but in a way that didn’t involve using West’s words.

D
Stuart’s work was not entirely free from West’s influence.

Strongly supported. The historian points out evidence showing potential influence, including meetings with West, friendship with one of West’s students, and use of distinctive language also used by West. This isn’t a “must be true” conclusion, but it is most strongly supported.

E
Because of Stuart’s influence on other people, West’s terminology is now commonplace.

Unsupported. Although we know the terminology is now commonplace, that stimulus doesn’t tell us why it became commonplace.


13 comments

One theory to explain the sudden extinction of all dinosaurs points to “drug overdoses” as the cause. Angiosperms, a certain class of plants, first appeared at the time that dinosaurs became extinct. These plants produce amino-acid-based alkaloids that are psychoactive agents. Most plant-eating mammals avoid these potentially lethal poisons because they taste bitter. Moreover, mammals have livers that help detoxify such drugs. However, dinosaurs could neither taste the bitterness nor detoxify the substance once it was ingested. This theory receives its strongest support from the fact that it helps explain why so many dinosaur fossils are found in unusual and contorted positions.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that “overdoses” on plants called angiosperms could’ve caused the sudden extinction of all dinosaurs. She bases this on the fact that dinosaurs couldn’t taste the plant’s bitterness or detoxify its poison, and that many dinosaur fossils are found in unusual and contorted positions.

Notable Assumptions
The author assumes that the fossils’ contorted positions are caused by poisoning from angiosperms, without considering other possible explanations for their positions.
The author assumes that, just because dinosaurs couldn’t avoid angiosperms by tasting their bitterness, they couldn’t avoid them at all. She thus assumes that dinosaurs were eating any angiosperms, a point which is never established.
She also assumes that angiosperms, which were “potentially lethal,” were deadly enough to cause the immediate extinction of all dinosaurs.

A
Many fossils of large mammals are found in contorted positions.
(A) undermines the theory by showing that there must be some other cause for the contorted shapes of large animals’ fossils. Most mammals avoided angiosperms but many still have contorted fossils. So, something other than angiosperms must have caused those fossil positions.
B
Angiosperms provide a great deal of nutrition.
This doesn’t weaken the argument because, even if angiosperms did provide nutrition, they were also poisonous. We also still don’t know that dinosaurs ate angiosperms in the first place.
C
Carnivorous dinosaurs mostly ate other, vegetarian, dinosaurs that fed on angiosperms.
By showing that some dinosaurs ate angiosperms, (C) slightly strengthens the argument. It doesn't challenge the author's theory or her assumptions that angiosperms were toxic enough to cause dinosaurs' extinction or that the contorted fossil positions were due to these plants.
D
Some poisonous plants do not produce amino-acid-based alkaloids.
This doesn’t change the fact that angiosperms do produce amino-acid-based alkaloids. So it does nothing to weaken the theory or to show that the author’s many assumptions are invalid.
E
Mammals sometimes die of drug overdoses from eating angiosperms.
We still don’t know that dinosaurs ever ate angiosperms, but (E) shows that angiosperm overdoses can cause death. So, if anything, this slightly strengthens the theory by confirming that angiosperms are poisonous enough to occasionally kill mammals.

36 comments

There are two ways to manage an existing transportation infrastructure: continuous maintenance at adequate levels, and periodic radical reconstruction. Continuous maintenance dispenses with the need for radical reconstruction, and radical reconstruction is necessitated by failing to perform continuous maintenance. Over the long run, continuous maintenance is far less expensive; nevertheless, it almost never happens.

"Surprising" Phenomenon
Why are highways rarely maintained continuously when doing so is cheaper than rebuilding them periodically?

Objective
Any hypothesis resolving this discrepancy will state another difference between continuous maintenance and radical reconstruction that explains why continuous maintenance is rare. This difference will make continuous maintenance unattractive or unattainable despite its lower cost in the long run.

A
Since different parts of the transportation infrastructure are the responsibility of different levels of government, radical reconstruction projects are very difficult to coordinate efficiently.
This deepens the mystery. If radical reconstruction is more difficult than continuous maintenance, why is it more common?
B
When funds for transportation infrastructure maintenance are scarce, they are typically distributed in proportion to the amount of traffic that is borne by different elements of the infrastructure.
This is not relevant. It is not implied whether infrastructure bearing heavy traffic is more or less likely to receive funds for continuous maintenance.
C
If continuous maintenance is performed at less-than-adequate levels, the need for radical reconstruction will often arise later than if maintenance had been restricted to responding to emergencies.
This deepens the mystery. If even sporadic maintenance delays the expensive radical reconstruction projects, even imperfect continuous maintenance is a worthwhile investment.
D
Radical reconstruction projects are, in general, too costly to be paid for from current revenue.
This does not explain why radical reconstruction projects are more common than continuous maintenance. It is not implied whether projects funded with current revenue are more or less favorable than those not funded with current revenue.
E
For long periods, the task of regular maintenance lacks urgency, since the consequences of neglecting it are very slow to manifest themselves.
This explains why continuous maintenance is so rare. Though cheaper in the long run, it is not perceived as urgent, and so receives a low priority.

9 comments