Arguments Test – Solutions
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1. The petrochemical industry claims that chemical waste dumps pose no threat to people living near them. If this is true, then why do they locate the plants in sparsely populated regions? By not locating the chemical dumps in densely populated areas the petrochemical industry tacitly admits that these chemicals are potentially dangerous to the people living nearby.
Which of the following, if true, would most weaken the author’s argument?
(A) Funding through the environmental Super Fund to clean up poorly run waste dumps is reserved for rural areas only.
(B) Until chemical dumps are proven 100% safe, it would be imprudent to locate them were they could potentially do the most harm.
(C) Locating the dumps in sparsely populated areas is less expensive and involves less government red tape.
(D) The potential for chemicals to leach into the water table has in the past been underestimated.
(E) People in cities are more likely to sue the industry if their health is harmed by the dumps.
Correct Answer: (C)
Solution: The suppressed false premise of the argument is that all things being equal there is no reason to prefer locating the sites in sparsely populated areas. To weaken the argument, we need to show it is not true that all things are equal. In other words, there are advantages other than safety in locating the sites in sparsely populated areas. Choice (C) gives two possible advantages–cost and ease. Hence (C) is the answer.
2. The news media is often accused of being willing to do anything for ratings. However, recent action by a television network indicates that the news media is sometimes guided by moral principle. This network had discovered through polling voters on the east coast that the Republican candidate for President had garnered enough votes to ensure victory before the polls closed on the west coast. However, the network withheld this information until the polls on the west coast closed so that the information would not affect the outcome of key congressional races.
Which one of the following most strengthens the argument?
(A) The network had endorsed the Republican candidate for President.
(B) The network expected its ratings to increase if it predicted the winner of the presidential race, and to decrease if did not predict the winner.
(C) A rival network did predict a winner of the presidential race before the polls on the west coast closed.
(D) The network believed that it would receive higher ratings by not predicting the winner of the presidential race.
(E) The network feared that predicting the winner of the presidential race could so anger Congress that it might enact legislation preventing all future polling outside of voting centers.
Correct Answer: (B)
Solution: The suppressed premise in this argument is that the network hurt itself by not predicting the winner of the presidential race, or at least did not help itself. To strengthen the argument, we need to show that this assumption is true. Choice (B) implies that this is the case by stating that the network expected to lose ratings if it did not predict a winner. Hence the answer is (B).
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3. To avoid economic collapse, Russia must increase its GNP by 20%. However, due to the structure of its economy, if the 20% threshold is reached, then a 40% increase in GNP is achievable.
Assuming that the above statements are true, which one of the following must also be true?
(A) If ethnic strife continues in Russia, then a 20% increase in GNP will be unattainable.
(B) If a 40% increase in Russia’s GNP is impossible, its economy will collapse.
(C) If Russia’s GNP increases by 40%, its economy will not collapse.
(D) If the 20% threshold is reached, then a 40% increase in GNP is achievable and a 60% increase is probable.
(E) If Russia’s economy collapses, then it will not have increased its GNP by 40%.
Correct Answer: (B)
Solution: Diagramming will show this seemingly difficult problem to be simply an application of the contrapositive rule of logic: in an if-then statement, negating the conclusion also negates the premise. The sentence “To avoid economic collapse, Russia must increase its GNP by 20%” can be reworded as “if Russia does not increase its GNP by 20%, its economy will collapse.” This in turn can be symbolized as
Where the arrow, ->, stands for “if …, then ….
Next, symbolize the clause “if the 20% threshold is reached, then a 40% increase is achievable” as
Applying the contrapositive to this statement yields
Using the transitive property (If a = b and b = c, then a = c) to combine this with the first symbol statement yields
In other words, if a 40% increase in GNP is unattainable, the economy will collapse. This is precisely what choice (B) states. The answer is (B).
4. Rebecca: When I went hiking in the mountains the other day, every bird that scolded me was a Steller’s Jay, and every Steller’s Jay I saw scolded me.
Which one of the following statements can be inferred from Rebecca’s observations?
(A) The only jays that Rebecca saw while hiking were Steller’s Jays.
(B) There were no Gray Jays in the area where Rebecca hiked.
(C) While she was hiking, no Gray Jays scolded Rebecca.
(D) All the jays that Rebecca saw scolded her.
(E) Rebecca did not see any Gray Jays while she was hiking.
Correct Answer: (C)
Solution: The passage contains an embedded if-then statement. “Every bird that scolded me was a Steller’s Jay” can be transformed into: If the bird scolded me, then it was a Steller’s Jay. This can be diagrammed as
Where the arrow, ->, stands for “if …, then ….
Keep this diagram in mind as you consider the answer selections.
(A). No. The passage indicates that every bird that scolded Rebecca was a Steller’s Jay. Stating it another way, a bird scolded Rebecca if and only if it was a Steller’s Jay. The passage doesn’t preclude the possibility that Rebecca saw other types of jays that didn’t scold her.
(B) No. Remember the diagram above, BS->SJ. Gray Jays are not in the equation, but the equation indicates that if Rebecca saw any Gray Jays, they didn’t scold her.
(C) Yes. Review the diagram again, BS->SJ. If a particular bird scolded Rebecca, then it must have been a Steller’s Jay, not a Gray Jay. Let’s apply the contrapositive rule of logic to the diagram (In an if-then statement, negating the conclusion also negates the premise):
not SJ->not BS
A Gray Jay is not a Steller Jay. The hypothesis of the if-then contrapositive statement, not SJ->not BS, is thus supported. As a result, the conclusion not BS, must follow. No Gray Jays scolded Rebecca.
(D) No. Unless all the jays Rebecca saw were Steller’s Jays (which we do not know), this statement does not follow. This statement is not supported by the diagram, which is limited to Steller Jays.
(E) No. Again, consider the diagram, BS->SJ. It does not exclude Gray Jays, but it does not allow them to scold Rebecca. So again, Rebecca could have seen Gray Jays, but they didn’t scold her as she hiked.
5. Democracy is the best form of government yet created. Therefore, we must be vigilant in its defense; that is, we must be prepared to defend the right to freedom. Because this right is fundamental to any progressive form of government, it is clear that democracy is better than any other form of government.
Which one of the following illustrates the same flawed reasoning as found in the passage?
(A) I never get a headache when I eat only Chinese food, nor when I drink only wine. But when I eat Chinese food and drink wine, I get a headache. So the combination of the two must be the cause of my headaches.
(B) The two times I have gone to that restaurant something bad has happened. The first time the waiter dropped a glass and it shattered all over the table. And after the second time I went there, I got sick. So why should I go there again–something bad will just happen again.
(C) I would much rather live a life dedicated to helping my fellow man than one dedicated to gaining material possessions and seeing my fellow man as a competitor. At the end of each day, the satisfaction of having helped people is infinitely greater than the satisfaction of having achieved something material.
(D) I’m obsessed with volleyball; that’s why I play it constantly. I train seven days a week, and I enter every tournament. Since I’m always playing it, I must be obsessed with it.
(E) In my academic studies, I have repeatedly changed majors. I decide to major in each new subject that I’m introduced to. Just as a bee lights from one flower to the next, tasting the nectar of each, I jump from one subject to the next getting just a taste of each.
Correct Answer: (D)
Solution: The argument in the passage is circular (and filled with non-sequiturs). It is incumbent on the writer to give evidence or support for the conclusion. In this argument, though, the writer first states that democracy is the best government, the rest is merely “noise,” until he restates the conclusion.
Choice (A) is a reasonably valid causation argument–eliminate. (B) argues by generalization. Although it is of questionable validity, it is not circular because the conclusion, “it will happen again,” is not stated, nor is it implicit in the premises–eliminate. (C) is not circular because the conclusion is mentioned only once–eliminate. (D) begins by stating, “I’m obsessed with volleyball.” It does not, however, provide compelling evidence for that claim: training seven days a week, rather than indicating obsession, may be required for, say, members of the Olympic Volleyball Team. Furthermore, the argument repeats the conclusion at the end. So it is circular in the same manner as the original. Hence (D) is our answer.
6. Either restrictions must be placed on freedom of speech or certain subversive elements in society will use it to destroy this country. Since to allow the latter to occur is unconscionable, we must restrict freedom of speech.
The conclusion above is unsound because
(A) subversives do not in fact want to destroy the country
(B) the author places too much importance on the freedom of speech
(C) the author fails to consider an accommodation between the two alternatives
(D) the meaning of “freedom of speech” has not been defined
(E) subversives are a true threat to our way of life
Correct Answer: (C)
Solution: The arguer offers two options: either restrict freedom of speech, or lose the country. He hopes the reader will assume that these are the only options available. This is unwarranted. He does not state how the so-called “subversive elements” would destroy the country, nor for that matter why they would want to destroy it. There may be a third option that the author did not mention; namely, that society may be able to tolerate the “subversives”; it may even be improved by the diversity of opinion they offer. The answer is (C).