Logical Reasoning · Weaken

PrepTest 143 · Section 3 · Question 13

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type

Weaken

The one idea it tests

An argument that rests on 'the sole purpose of this arrangement is X' is popped by showing another purpose.

The basic logic

Find the claim that a role exists only to benefit the person filling it. Then look for a fact showing the role also serves the other side's own interests. That breaks 'sole purpose' and pops the conclusion.

Tiny words that decide it

“sole”
“only”
“if not”
“thus”

Playground logic

Grandpa's top bun: Tommy's dog walking is not a real chore. His patty: the only purpose is to let Tommy earn money for a bike. Pop it by showing Grandpa is replacing the paid dog walker with Tommy to save cash, so the job serves Grandpa too.

Step 2 · The kid story

Is Walking Biscuit a Real Chore?

Tommy walks Biscuit every afternoon and gets a dollar each time. He wants a gold star on the family chore chart too. Grandpa shook his head. "That's not a real chore, kiddo. The only reason you walk Biscuit is to earn money for that bike. If you didn't want the bike, you wouldn't be walking him at all." Tommy looked at Lulu. Lulu looked at her clipboard. "Grandpa, last week you canceled Bark Buddies, the walking service. You said paying them cost too much and Tommy was cheaper." Grandpa coughed. "Well, I..." Biscuit sat down firmly, as if voting for the gold star. Priya whispered, "If Grandpa needs the walking done to save money, it is not only about Tommy's bike."

Step 3 · Try the model question

Grandpa: Tommy's dog walking should not count as a real chore. Yes, he walks Biscuit and gets paid. But the only purpose is to help him save for a bike. If he did not want the bike, he would not walk Biscuit at all.

Which fact, if true, most undermines Grandpa's argument?

Step 4 · The courtroom tale

The Volunteer Lifeguard

In a fictional town, a teen asked to be listed on the beach staff roster. The park director's lawyer argued, "Her post exists only so she can earn badge hours for her scout award. Without the award, she would not be there." Mr. Whitfield rose, holding a memo. "Your Honor, this is the park's own budget plan. It proposes cutting two paid lifeguards and filling their chairs with badge-hour teens to save money." He let it sit. "If the park is using her to save money, her post is not only for her benefit." The judge looked at the memo, then at the director. "That argument just sprang a leak."

Step 5 · Work the real question

Open PrepTest 143, Section 3, Question 13 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Locate the conclusion and the key premise that a role exists for one purpose only. Ask: what fact would show that the arrangement also serves the institution itself? Predict something like 'the other side relies on these people to save money or fill a need.' Then scan for the choice that gives the institution its own reason for the arrangement. Ignore choices about motives, effort or comparisons that leave the 'sole purpose' claim untouched.