PrepTest 143, Section 3, Question 9
We know that if life ever existed on(34 more words not shown)
The pattern of reasoning in(14 more words not shown)
- AWe know that(22 more words not shown)
- BIf we have(22 more words not shown)
- CHendricks will win(26 more words not shown)
- DIf rodents are(34 more words not shown)
- EIf their army(34 more words not shown)
Reading the argument
Not finding signs of life isn't necessarily the same as there being no signs to find.
The rule says that if life ever existed on the Moon, there would be signs of it. Then we learn that numerous visits have failed to find any. Could the evidence be somewhere nobody has examined? Imagine traces buried deep below the surface. In that case, the rule could be true and the searches could come up empty, even though life had existed.
What we’re looking for
We need to match the reasoning, including that gap. The structure is: if something happened, there would be evidence; efforts to find that evidence haven't produced it; therefore the thing never happened. Pay attention to “haven't found.” An argument that establishes that no evidence exists would make a different move.
Working the answers
- A
Knowing that a particular spy is a traitor doesn't give us a general rule about all spies. And not knowing that the general is a traitor doesn't establish that the general isn't one. Although A also makes a questionable move from limited knowledge, it lacks the original's general connection between an event and signs of that event, followed by unsuccessful attempts to find those signs.
- B
The first part fits: if we have mayonnaise, it would be in the refrigerator. But an almost-empty refrigerator could still contain mayonnaise. B doesn't say that someone searched the refrigerator and found no mayonnaise. It also reaches a tentative conclusion—unlikely—where the original rules out past life outright. To match more closely, it would need a failed search followed by the categorical conclusion that we have none.
- C
This does give a condition: Hendricks can win only if fighting crime is voters' primary concern. But the next fact is about Hendricks's support for tougher penalties, not evidence that voters have the required concern. The argument then predicts a win. It doesn't report a failed search for an expected sign and use that failure to rule something out.
- D
Here we find the signs and conclude that rodents caused the lost grain. The original fails to find signs and concludes that life never existed. Those moves run in opposite directions. To match, D would need unsuccessful searches for rodent signs followed by the conclusion that rodents weren't responsible.
- ECorrect
Planning an attack corresponds to life having existed. Troop movements or a weapons transfer are the signs that the plan would produce, just as lunar life would leave signs. Intelligence reports show no indication of either, corresponding to the visits that have found no signs of life. The argument concludes there is no attack planned.
The two possible indicators don't spoil the match: the reports have failed to reveal either kind of evidence. The same gap remains. The indicators could exist without appearing in the reports, just as signs of life could exist without the visitors having found them.
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