Identifying Necessary Assumptions

Art historian: The newly discovered 16th-century painting *The Solitary Scholar* contains lapis lazuli, a blue pigment that was exorbitantly expensive at the time. Only artists backed by wealthy patrons could afford to use lapis lazuli extensively in their works. Given that historical records confirm the artist, Vincenzo, died in poverty and never secured a wealthy patron, *The Solitary Scholar* must have been a collaborative effort with an artist who could afford such materials.

Which one of the following is an assumption required by the art historian's argument?

Urban Sociologist: To foster a stronger sense of community, the city council is converting several downtown streets into pedestrian-only zones. Currently, residents rarely interact with one another in these areas because heavy vehicle traffic makes the streets excessively noisy and dangerous. By eliminating cars from these specific streets, the city will ensure that residents socialize more frequently, thereby successfully strengthening community bonds.

Which one of the following is an assumption required by the urban sociologist's argument?

Paleontologist: Fossilized remains of the ancient amphibian *Dendrerpeton* have been found exclusively in geological formations corresponding to harsh, arid desert environments of the late Carboniferous period. Since all modern amphibians require constant access to substantial bodies of freshwater to survive, *Dendrerpeton* must have possessed specialized physiological adaptations for water retention that modern amphibians lack.

Which one of the following is an assumption on which the paleontologist's argument depends?

Historian: The collapse of the Bronze Age civilization of Alashiya was long attributed to a massive earthquake. However, sediment core analyses reveal a multi-decade drought immediately preceding the collapse. Furthermore, contemporaneous administrative tablets show an abrupt shift from recording luxury trade to issuing frantic requests for grain. Therefore, the collapse was fundamentally driven by climatological resource scarcity rather than sudden seismic activity.

Evaluate the following statement as true or false regarding the argument above:
The statement 'The abrupt shift in the administrative tablets to requests for grain was not primarily a response to agricultural devastation wrought by a sudden earthquake' functions as a necessary assumption for the historian's conclusion.

Ecologist: In the region's heavily logged forests, the population of the native spotted owl has plummeted. Conservationists argue that the logging of old-growth trees destroyed the owl's necessary nesting habitat, causing the decline. However, a recent survey shows that the invasive barred owl, which aggressively competes with the spotted owl for prey, recently expanded its range into these exact same logged forests. Therefore, the drastic decline in the spotted owl population is primarily due to competition from the invasive barred owl, rather than the loss of nesting habitat.

Which one of the following is an assumption on which the ecologist's argument depends?

Paleontologist: The fossilized remains of the newly discovered dinosaur G. antiquus reveal unusually large eye sockets compared to its contemporary relatives. Because exceptionally large eyes are typically an evolutionary adaptation for maximizing visual acuity in low-light conditions, G. antiquus must have been a nocturnal species that hunted exclusively during the night.

Which one of the following is an assumption required by the paleontologist's argument?

Historian: A newly deciphered administrative tablet from the ancient city of Oakhaven lists the daily rations given to the city's palace guards. These rations consisted entirely of barley and dried fish. In contrast, military records from the neighboring city of Riverton from the same period explicitly mention supplementary rations of figs and olives for their guards. Therefore, Oakhaven's palace guards must have had a less varied diet than Riverton's guards.

Which one of the following is an assumption required by the historian's argument?

Coffee Importer: Our cooperative should immediately convert all conventional sun-grown coffee farms to shade-grown coffee. Although shade-grown farming yields $30\%$ fewer beans per hectare, shade-grown specialty beans sell for a $50\%$ premium over conventional beans. Therefore, making this complete conversion will undoubtedly increase the cooperative's overall profits.

Which of the following are necessary assumptions upon which the coffee importer's argument depends? Select all that apply.

Marine biologist: The population of the rare blue-finned reef fish in the Coral Bay sanctuary will likely begin to increase over the next few years. Last year, authorities implemented a strict ban on all fishing in the sanctuary. Since the ban took effect, the number of blue-finned reef fish caught by illegal fishers has plummeted. This critical reduction in human-caused mortality provides the species with the necessary conditions to replenish its numbers.

Which one of the following is an assumption required by the marine biologist's argument?

Archaeologist: Recent excavations of the ancient settlement of Tlanex indicate a stark division in material culture. The highland sector contains thousands of intricately carved jade artifacts, whereas the lowland sector contains almost exclusively unpolished clay implements. Because the jade artifacts required hundreds of hours of specialized labor to produce, they were undoubtedly luxury items of immense value. Consequently, the inhabitants of the highland sector must have belonged to a significantly higher socioeconomic class than the inhabitants of the lowland sector.

Which one of the following is an assumption required by the archaeologist's argument?

Read the argument below and evaluate whether the provided statement functions as a necessary assumption.

Historian: The invention of writing must have been driven by the need to manage the increasingly complex trade networks of early agricultural surpluses, not by the administrative demands of large-scale monumental building projects. The traditional theory favoring monumental architecture as the primary catalyst is decisively refuted by recent excavations at Oruk, which reveal that complex record-keeping systems were fully established centuries before the construction of any such monuments.

Statement: The administrative demands associated with large-scale monumental building projects did not arise centuries before the actual physical construction of such monuments began.

Biologist: The prehistoric canid *Aetocyon* must have lived and hunted in large social groups. The recent discovery of fossilized *Aetocyon* reveals that these animals had highly specialized jaw structures adapted exclusively for crushing large bones. In the modern world, bone-crushing predators such as spotted hyenas hunt in large, coordinated packs in order to take down large prey.

Which of the following are necessary assumptions on which the biologist's argument depends? (Select all that apply.)

Retail Analyst: A regional hardware store recently replaced all its traditional cashier lanes with self-service checkout kiosks in an attempt to speed up the checkout process. However, since the transition, the average time a customer spends in the checkout area has actually increased by 15 percent. This shows that the self-service kiosks process individual purchases more slowly than the traditional cashiers did.

Which one of the following is an assumption on which the retail analyst's argument depends?

Business Analyst: To increase productivity, TechCorp recently transitioned to a four-day workweek without reducing employee pay. Studies consistently show that employees who are well-rested make fewer errors and complete their assigned tasks significantly faster. Therefore, TechCorp's overall weekly output will certainly not decrease as a result of this schedule transition.

Which of the following statements must be assumed in order for the analyst's conclusion to be properly drawn? Select all that apply.

City Planner: To alleviate traffic congestion on the downtown bridge, the city council should implement a dynamic toll system that charges higher fees during peak commuting hours. A recent trial of a similar dynamic toll system on the primary highway of the neighboring city of Oakville resulted in a 20% reduction in peak-hour traffic volume within three months. Thus, our implementation of this system will successfully reduce peak-hour traffic on the downtown bridge.

Which of the following statements are necessary assumptions upon which the city planner's argument depends? (Select all that apply)

To increase productivity, a software company is mandating a switch from traditional keyboards to new ergonomic keyboards for all its programmers. The manufacturer of the ergonomic keyboards has proven that they reduce typing strain by 40 percent. Therefore, the company's programmers will definitely produce more code per week after the switch.

Which of the following statements are necessary assumptions required by the argument? (Select all that apply)

Mayor: We should build a new community pool in the town center. Swimming is an excellent form of cardiovascular exercise that can be enjoyed by people of all ages. Currently, our town's residents have very limited options for cardiovascular exercise due to a lack of public facilities. Therefore, building this new pool will significantly improve the overall cardiovascular health of our residents.

Which one of the following is an assumption on which the mayor's argument depends?

Consider the following argument.

Marine Biologist: To restore the local sea otter population, we must restrict commercial fishing in the bay. Commercial fishing depletes the population of sea urchins, which are the primary food source for sea otters in this region, so limiting fishing will lead to an increase in otter numbers.

Statement: The marine biologist's argument logically requires the assumption that restricting commercial fishing in the bay will succeed in increasing the population of sea urchins.

City official: To reduce traffic congestion downtown, we should build a new subway line connecting the suburbs to the city center. A recent survey showed that 70 percent of suburban commuters would take the subway if it were available.

Which one of the following is an assumption on which the city official's argument depends?

Epidemiologist: To successfully eradicate the Varia strain of the virus in the metropolitan area, at least 80 percent of the population must be vaccinated. The only currently approved vaccine, Novovax, requires two doses administered exactly three weeks apart to provide immunity. Public health records indicate that while 85 percent of the metropolitan population received the first dose of Novovax, a significant portion of those individuals never returned for the second dose. Consequently, the public health initiative to eradicate the Varia strain will fail.

Which of the following statements must be assumed in order for the epidemiologist's conclusion to be logically drawn? (Select all that apply.)