PrepTest 107, Section 3, Question 10
The only motives that influence all human actions(16 more words not shown)
The reasoning in the argument(5 more words not shown)
- Adenies that an(22 more words not shown)
- Btakes the occurrence(23 more words not shown)
- Cconcludes that a(23 more words not shown)
- Dconcludes that, because(27 more words not shown)
- Eundermines its own(18 more words not shown)
Reading the argument
Always present doesn't mean most important.
The premise singles out self-interest as the source of motives that influence every human action. It doesn't say that no other motives ever influence us. Other motives could affect some actions without being present in all of them.
Now imagine that self-interest is only a tiny part of each decision—say, 1 percent. In one decision, concern for a friend does most of the work. In another, a sense of duty does. Self-interest could keep appearing without being the strongest influence in either decision. The percentage is just an illustration; the point is that frequency and strength are different things.
Think of oxygen: people keep breathing it, but that doesn't make thinking about oxygen their chief concern throughout the day. Constant presence doesn't settle what matters most to the decisions being made.
What we’re looking for
The author jumps from self-interest's presence across human actions to its being the chief influence on them. For the flaw question, that's what I want to describe: the argument treats an influence's occurrence as proof that it outweighs the other influences.
Working the answers
- A
The author doesn't deny that something common to a pattern can help explain that pattern. The author uses a common influence to reach a claim about its importance. A describes rejecting a possible contribution to an explanation; our author instead gives the stated influence more weight than the premise establishes.
- BCorrect
The argument takes the occurrence of an influence as showing that it outweighs other influences. Self-interest is the influence, human actions are the events, and “chief” makes the claim about comparative importance. The premise doesn't provide that comparison. Self-interest could be a recurring but minor factor.
- C
There is no move from one time period to every time period. The passage doesn't compare past human behavior with present or future behavior. It moves from the reach of an influence across actions to the strength of that influence.
- D
This puts the reasoning in the wrong order. It starts with an influence already being paramount—the most important—and concludes that it is the only influence. Our argument starts with self-interest's recurring presence and tries to establish that it is the chief influence.
D also ends with exclusivity. The actual conclusion doesn't say that no other influence exists. Something can be the chief influence while other influences still contribute.
- E
The conclusion does not contradict the premise. Self-interest could be both present across actions and the chief influence on them. The problem is that the first claim doesn't establish the second. An unsupported conclusion and a contradiction are different mistakes.
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