PrepTest 129 · Section 2 · Question 1 (Principle)

Step 1 · Pre-Question Guidance · read this first

Question type

Principle

The one idea it tests

Find the rule that, if you held it, would hand you this exact conclusion.

The basic logic

Collect every reason the arguer leans on (here there are two) and look for a principle that uses all of them to land on the same kind of 'should' conclusion. A rule that needs only one of the reasons, or that goes broader or narrower than the conclusion, does not fit.

Tiny words that decide it

“should”
“never”
“and”
“cannot”

Playground logic

Grandpa's patty has two pieces: glitter can't make Tommy's volcano erupt any higher, and glitter makes a giant mess. His top bun is a 'never.' The matching principle has to use BOTH patty pieces: if a thing can't fix the problem and it also brings a downside, don't use it.

Step 2 · The kid story

The Glitter Volcano

Tommy wanted his science fair volcano to blast higher than anyone's. His plan: pour a whole jar of glitter into the crater. Grandpa looked over his newspaper. "Tommy, the blast comes from the fizzing stuff inside, the baking soda and the vinegar. Glitter doesn't fizz. It just rides along." Tommy frowned. "So it won't help?" "Not one inch," said Grandpa. "And there's more. Glitter sticks to the cat, the carpet, and your eyebrows for a month. Mr. Whiskers still sparkles from your birthday." Mr. Whiskers sneezed a tiny sparkle. "So," Grandpa finished, "you should never use glitter to make a volcano blast higher." Lulu wrote on her clipboard: Can't help + makes trouble = don't do it.

Step 3 · Try the model question

Grandpa: The height of a volcano blast comes from the fizzing reaction, and glitter does not fizz, so glitter cannot make the blast higher. Glitter also makes a mess that lasts for weeks. So you should never use glitter to make a volcano blast higher.

Grandpa's reasoning fits best with which one of these rules?

Step 4 · The courtroom tale

The Case of the Squeaky Hinge

Mr. Whitfield snapped his suspenders. "Your Honor, the landlord painted over the squeaky door hinge. But the squeak comes from rusty metal rubbing metal. Paint does not stop rubbing, so paint cannot stop the squeak. Worse, the paint glued the door half shut, and my client climbed out a window for a week." The judge peered over her glasses. "Your point?" "A landlord should never paint a hinge to cure a squeak." The judge nodded. "So your rule is: do not use a fix that cannot solve the problem when it also creates a new one." "Exactly, Your Honor. Two reasons, one rule."

Step 5 · Work the real question

Open PrepTest 129, Section 2, Question 1 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion and notice whether it says 'should' or 'never.' List every reason given; count them. Then test each choice: does it use all of the reasons, and does applying it produce exactly that conclusion? Cross off rules that rely on only one reason, that would require more than the argument says, or that point the other way. The winner fits the argument like a glove, not a mitten.