Logical Reasoning · Weaken

PrepTest 113 · Section 3 · Question 16

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 author grants one reason for a ban, knocks down a different reason, and concludes no ban, forgetting the first reason might apply too.

The basic logic

Find the reason the author accepts for banning things. Then find the item the author says should be allowed, and the reason the author defeated. Pop the argument by showing the accepted reason also covers the allowed item.

Tiny words that decide it

“because”
“never”
“however”
“therefore”

Playground logic

Marcus agrees fireworks are banned at the treehouse because they are dangerous. He beats Lulu's messiness argument and declares marbles should be allowed. But if spilled marbles make kids slip and fall, Marcus's own safety rule bans them, and his top bun pops.

Step 2 · The kid story

The Treehouse Marble Debate

Grandpa's treehouse rule was simple: no fireworks, because they are dangerous. Then Lulu proposed a second rule. "No giant buckets of marbles. They are messy." Marcus laughed. "Messy? Everything up here is messy! Paint, mud, cracker crumbs. Nobody bans those for being messy. Besides, we have bigger problems, like the cracked ladder rung. So marbles stay." Frankie and Sharon both nodded, which never happens. But Grandpa scratched his chin. "Marcus, you beat the messy argument. Fair enough. But remember why we banned fireworks? Danger. Last summer Kevin stepped on a spilled marble and nearly slid right off the platform." Marcus went quiet. "So marbles might break the danger rule, not the messy rule." Lulu wrote it down with a big smile.

Step 3 · Try the model question

Fireworks are banned from the treehouse because they are dangerous. Lulu wants buckets of marbles banned for being messy. But nearly everything in the treehouse is messy, and nothing is banned for that. Besides, there are bigger problems, like the cracked ladder rung. So marbles should be allowed in the treehouse.

Which one of the following, if it were true, most seriously undermines Marcus's conclusion?

Step 4 · The courtroom tale

The Case of the Garden Gnomes

The homeowners' board banned electric fences because they can hurt people. A neighbor then asked the board to ban giant stone gnomes for being ugly. Attorney Vance argued, "Ugly? Half the street is ugly! Pink flamingos, plastic wells. None are banned for looks. So the gnomes stay." Mr. Whitfield rose. "Counsel defeated the ugliness argument, I grant. But the board bans things that hurt people. These gnomes weigh two hundred pounds and sit on a crumbling wall over the sidewalk. One already toppled near a stroller." The judge raised her eyebrows. "Then the gnomes fail the very test counsel accepted."

Step 5 · Work the real question

Open PrepTest 113, Section 3, Question 16 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Separate the two reasons in the argument: the one the author accepts as good grounds for a ban and the one the author attacks. Then read the conclusion about what should be allowed. Look for the answer that shows the allowed item actually meets the accepted reason. Ignore answers that only add to the author's attack on the weak reason or that touch side remarks.