12. Assumption Question
1. (p.70)
After examining the bodies of a dozen beached whales and finding evidence of bleeding around the animals' eyes and brains as well as lesions on their kidneys and livers, environmental groups fear that the Navy's use of sonar is causing serious harm to marine animals. A leading marine biologist reports that sonar induces whales to panic and surface too quickly, which causes nitrogen bubbles to form in their blood.
Fact
1. Beached whales have bleeding around the animals' eyes and brains as well as lesions on their kidneys and livers. (r)
2. Sonar induces whales to panic which causes nitrogen bubbles to form in their blood. (p -> q)
Conclusion
Environmental group argues that use of sonar is causing serious harm to marine animals. (p -> r)
Serious harm == bleeding around the animals' eyes and brains as well as lesions on their kidneys and livers.
Assumption
q -> r : Nitrogen bubbles to form in whale's blood makes harm to marine animals
2. (p.71)
If television editors did not exercise control over television commercials, many commercials would make exaggerated claims for their products. After all, one-third of the commercials reviewed each year by television editors are rejected and returned to the advertising agencies for reivisons, in many cases because claims made in the commercials are not sufficiently documented.
Fact
Not sufficiently document -> rejected
Conclusion
Exaggerated -> rejected
Assumption
Exaggerated -> Not sufficiently document
13. Strengthen Question
1. (p.72)
Country Y uses its scarce foreign-exchange reserves to buy scrap iron for recycling into steel. Although the steel thus produced earns more foreign exchange than it cost, that policy is foolish. Country Y's own territory has vast deposits of iron ore, which can be mined with minimal expenditure of foreign exchange.
Claim : policy is foolish
Fact
1. Y has vast deposits of iron ore that could make minimal expenditure.
2. use foreign exchange to buy scrap iron
Assumption
Using iron ore other than scrap iron makes minimal expenditure.
2. (p.73)
Many breakfast cereals are fortified with vitamin supplements. Some of these cereals provide 100 percent of the recommended daily requirement of vitamins. Nevertheless, a well-balanced breakfast, including a variety of foods, is a better source of those vitamins than are such fortified breakfast cereals alone.
Fact
Many breakfast cereals has sufficient vitamin supplement
Claim
Variety of food is better option to take sufficient vitamin.
Assumption
Variety of food is better than cerals alone to take sufficient vitamin.
14. Weaken Question
1. (p.74)
Psychologists have just completed an extensive study of recently divorced parents in order to determine which factors contributed most to the dissolution of the marriage. The researchers found that in a great majority of the cases of failed marriages, the couple ate, on average, fewer than ten meals per week with each other. From this data, the psychologists have determined that a failure to spend time together during meal times is a major factor leading to divorce.
Fact
The great majority of the cases of failed marriages have few meal with each other.
Claim
Failure to spend time together during meal time is major factor leading to divorce.
Claim
There is only one factor that leading to divorce is failure to spend time together during meal time.
Critical Reasoning Sample Questions
1. (p.109)
'Life expectancy is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at an age that we consider the prime of life.
Fact : In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years.
Claim : Shorter life expectancy -> comparatively old
Assumption : If life expectancy is smaller, die earlier.
2. (p.109)
Homeowners aged 40 to 50 are more likely to purchase ice cream and are more likely to puchase it in larger amounts than are members of any other demographic group. The popular belief that teenagers eat more ice cream than adults must, therefore, be false.
Fact
Home owners aged 40 to 50 are more likely to purchase ice cream more than other group
Claim
Home owners aged 40 to 50 are eat more ice cream more than other group
Assumption
More purchase -> More consumption
3. (p.110)
A conservation group in the United States is trying to change the long-standing image of bats as frightening creatures. The group contends that bats are feared and persecuted solely because they are shy animals that are active only at night.
Fact
Image of bats as frightening creatures. (i.e. feared and persecuted)
Claim
Bats are shy animals that are active only at night.
Assumption
Only being active at night makes them frightening.
4. (p.110)
Hunter : Many people blame hunters alone for the decline in Greenrock National Forest's deer population over the past ten years. Yet clearly, black bears have also played an important role in this decline. In the past ten years, the forest's protected black bear population has risen sharply, and examination of black bears found dead in the forest during the deer hunting season showed that a number of them had recently fed on deer.
Fact 1
1. In the past ten years, the forest's protected black bear population has risen sharply.
2. Black bears found dead in the forest during the deer hunting season.
Claim
A number of bears had recently fed on deer
Assumption
Dead during deer hunting season -> fed on deer
5. (p.111)
In recent years many cabinetmakers have been winning acclaim as artists. But since furniture must be useful, cabinetmakers must exercise their craft with an eye to the practical utility of their product. For this reason, cabinetmaking is not art.
Fact 1
Furniture must be useful
Claim 1 (Fact 2)
Cabinetmakers make their craft useful.
Claim 2
Cabinet is not art
Assumption
Useful -> not art
6. (p.111)
Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on the fact that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles, researchers have concluded that the bowerbirds' building styles are a culturally acquired, rather than a genetically transmitted, trait.
