Logical Reasoning · Flaw

PrepTest 129 · Section 3 · Question 8

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

Step 1 · Pre-Question Guidance · read this first

Question type

Flaw

The one idea it tests

A slippery slope: assuming one small step must trigger a long chain of worse and worse steps.

The basic logic

Spot a 'if we do this once, then next, then next, then disaster' chain with no evidence for each link. The flaw is presuming the chain will happen just because the first step happens.

Tiny words that decide it

“if”
“then”
“soon”

Playground logic

Grandpa's top bun: no extra bedtime minutes for Tommy, even though tonight's reason is good. The patty is a slide: one late night leads to many, then to no bedtimes at all. Each step down the slide is just assumed, never shown.

Step 2 · The kid story

Grandpa and the Slippery Bedtime

Tommy wanted to stay up fifteen extra minutes to watch the moon eclipse. Even Grandpa admitted it was a good reason. But then Grandpa shook his head. "If I let you stay up tonight, soon you'll want extra minutes every night. Some of those reasons won't be any good. Before long, Lulu will want a later bedtime too, and then nobody in this house will have a bedtime at all! To keep order, the answer is no." Tommy looked at Lulu. Lulu looked at her clipboard. "Grandpa," she said, "you skipped a lot of steps. Why would one eclipse lead to no bedtimes ever?" Grandpa opened his mouth, then closed it. Biscuit barked in agreement.

Step 3 · Try the model question

Grandpa: Tommy has a good reason to stay up late tonight. But if I allow it, he will ask for extra time every night, then his sister will too, and soon the house will have no bedtimes at all. So I must say no.

Grandpa's reasoning is most open to which one of the following criticisms?

Step 4 · The courtroom tale

The Case of the One Free Sample

A grocery manager testified about why he fired a clerk. "She gave one customer a free grape to taste. If we allow one grape, soon customers will want free apples, then free bread, then they'll stop paying for anything, and the store will close!" Mr. Whitfield tugged his suspenders. "Your Honor, the witness has built a staircase with no proof that anyone will climb even the second step. Has any customer ever asked for free bread after a grape?" The manager coughed. "Not yet." "No further questions."

Step 5 · Work the real question

Open PrepTest 129, Section 3, Question 8 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion, then trace the chain of predicted consequences. Ask whether each link is supported or simply assumed. If the argument jumps from one small action to a big outcome through unsupported steps, that is the slippery slope. Choose the answer that names this abstractly, and reject answers naming flaws you cannot point to in the argument.