Logical Reasoning · Necessary Assumption

PrepTest 152 · Section 4 · 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

Necessary Assumption

The one idea it tests

If your own premise says people will do anything for a big edge, your fix must assume the forbidden extra does not give a big edge.

The basic logic

The argument says a ban won't work because people chase big advantages, then proposes a limited allowance that removes the danger. But by its own logic, people would break the limit if going over gave a big advantage. So it must assume going over the limit does not give a big edge.

Tiny words that decide it

“will not”
“only if”
“anything”

Playground logic

Frankie's patty: kids will will do anything for big fun, so banning the tall slide fails. Top bun: allow it, but only feet-first with a grown-up watching, and the bumps vanish. Secret sauce: head-first isn't a lot more fun than feet-first.

Step 2 · The kid story

The Tall Slide Rule

The playground's tall slide has been banned. Nobody listens. Frankie has a plan for the principal. "A ban on the slide won't stop anyone. It's too fun, and kids will do anything for big fun. So let us use it, but only feet-first, with a grown-up watching. Then nobody bonks their head." Sharon crosses her arms. "Hold on. You just said kids will do anything for big fun. What if head-first is way more fun than feet-first?" Frankie freezes. "Then they'd sneak head-first slides when the grown-up looks away." "Exactly," says Sharon. Priya sips her juice box. "Your plan needs head-first to not be a lot more fun. Pull that plank and your own rule gets broken by your own reason."

Step 3 · Try the model question

Frankie: A ban on the tall slide will not stop kids from using it, since it is great fun and kids will do anything for great fun. So the slide should be allowed, but only feet-first while a grown-up watches. Done that way, the bumps disappear.

Frankie's argument relies on which one of these?

Step 4 · The courtroom tale

The Midnight Snack Treaty

Judge Ferris read the proposal aloud. "The defendant, a teenager named Dex, argues that banning late snacks will fail because teenagers will do anything for a truly great snack. So snacks should be allowed, but only fruit, with a parent present. Then the crumbs on the couch disappear." Mr. Whitfield raised a hand. "Your Honor, by Dex's own rule, if a cookie were a truly greater snack than fruit, Dex would sneak cookies when the parent left." The judge nodded. "So this treaty only works if cookies are not much better than fruit." Dex looked at the cookie jar. The cookie jar looked back. "I may need to revise," said Dex.

Step 5 · Work the real question

Open PrepTest 152, Section 4, Question 13 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Note the premise about people doing anything for a big advantage. Then note the limited allowance the argument proposes. Ask: does the argument's own premise threaten its fix? Look for the choice that says going past the limit does not give a big advantage over staying within it. Negate it: if crossing the limit gave a big edge, the fix would fail. Skip choices about fairness or outside opinions.