Logical Reasoning · Principle (Justify)

PrepTest 151 · Section 3 · Question 10

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

Step 1 · Pre-Question Guidance · read this first

Question type

Principle (Justify)

The one idea it tests

A principle that justifies an argument is a general rule that, once accepted, makes the conclusion follow from the evidence.

The basic logic

Find the conclusion (one group should not be allowed to do something) and the evidence (that group lacks a certain amount of training, while another group has much more). The winning rule connects lacking that training to not being allowed. Look for a rule whose 'if' part matches the evidence and whose 'then' part matches the conclusion.

Tiny words that decide it

“should not”
“no one without”
“only if”

Playground logic

Ms. Rivera says Owen should not use the big hot glue gun. The patty: Owen had one short safety lesson, while her helpers trained for weeks. The secret sauce, as a rule: nobody without weeks of training gets the big glue gun. Snap that rule in and the top bun clicks shut.

Step 2 · The kid story

The Big Glue Gun

Craft day! Owen raced to the supply table and reached for the big hot glue gun, the one that drips like lava. "Not so fast," said Ms. Rivera. "You can't use that one." "But I took the safety lesson!" said Owen. "It was ten whole minutes!" Ms. Rivera smiled. "My craft helpers, Nadia and Priya, practiced with me for three weeks before they touched it. Ten minutes is not three weeks." Owen groaned and picked up the glue stick. Lulu wrote on her clipboard: 'Rule we need: no one uses the big glue gun without weeks of practice.' Priya peeked at it. "That's exactly the rule that makes Ms. Rivera's decision fair. Without it, she's just comparing minutes and weeks."

Step 3 · Try the model question

Ms. Rivera: Owen should not be allowed to use the big hot glue gun. His safety lesson lasted only ten minutes. My craft helpers, by contrast, practiced with it for three weeks before using it.

Which general rule, if accepted, best supports Ms. Rivera's conclusion?

Step 4 · The courtroom tale

The Zamboni Hearing

Judge Okafor tapped her gavel. "The rink manager says the new teenage employee may not drive the ice machine. Why?" Mr. Whitfield rose, suspenders gleaming. "Your Honor, the teen watched a one-hour video. The rink's senior drivers each spent two full seasons riding along before they ever took the wheel." Opposing counsel shrugged. "So? Lots of people learn fast." Mr. Whitfield nodded. "Fair. So here is the rule the rink posted on its wall: nobody drives the machine without at least two seasons of ride-along training. Once we accept that rule, the facts settle it. The teen lacks the training, so the teen may not drive." The judge read the posted rule. "Ruling for the rink."

Step 5 · Work the real question

Open PrepTest 151, Section 3, Question 10 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Name the conclusion, then list what the evidence says one group lacks compared with another. Predict a rule shaped like 'anyone who lacks this may not do that.' Check each choice: does its trigger match the evidence about the group, and does its result match the conclusion? Watch for rules that only say who may do something (wrong direction), rules about a different group, or rules that recommend more training instead of deciding permission.