Logical Reasoning · Flaw

PrepTest 101 · Section 2 · Question 1

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

Evidence that clears one part of something cannot, by itself, clear the whole thing.

The basic logic

Put a finger on exactly what the evidence covers. Then put a finger on exactly what the conclusion claims. If the conclusion covers a bigger area than the evidence, the gap is a Scope Shift (one part treated as the whole).

Tiny words that decide it

“so”
“no sign of”
“in every way”

Playground logic

Kevin's teacher checked his book report for spelling and found no mistakes. Marcus jumps from that to 'the report is perfect.' Spelling is one slice of a report, so the evidence is too small for the conclusion: a Scope Shift.

Step 2 · The kid story

The Perfect Book Report

Kevin turned in his book report about a dinosaur who opens a pizza shop. The next day Ms. Rivera handed it back with a sticky note: 'Spelling check: zero mistakes!' Marcus grabbed it and read it out loud like a news anchor. 'Breaking news! Kevin's report is perfect. Give him the gold star right now.' Lulu tapped her clipboard. 'The note only talks about spelling. What about whether he answered the question? What about the ending?' Kevin looked a little nervous. 'The ending is where the T. rex eats the whole shop.' Priya sipped her juice box. 'So the spelling is clean. That's real good news. But perfect means every part, and the note only checked one part.' Marcus slowly lowered the report. 'So it could be perfectly spelled and still have a very strange ending?' 'Very strange,' said Kevin proudly.

Step 3 · Try the model question

Ms. Rivera checked Kevin's book report for spelling and found no errors. Marcus concludes that Kevin's book report is perfect.

Which one of the following identifies a weakness in Marcus's reasoning?

Step 4 · The courtroom tale

The Brakes Were Fine

A buyer sued a used car dealer. The dealer's ad had promised a car 'in flawless condition.' The dealer's lawyer held up a mechanic's report. 'The brakes were tested. No problems found. My client acted honestly.' Mr. Whitfield hooked his thumbs in his suspenders. 'Your Honor, I accept every word of that report. The brakes were fine. But the ad did not say the brakes were flawless. It said the car was. The engine, the gearbox, the roof that leaked on my client's head in the first rainstorm: none of those were checked.' Judge Amari wrote a note. 'So the report is true, but the ad claims more than the report can carry.' 'Exactly, Your Honor. One clean part is not a clean whole.'

Step 5 · Work the real question

Open PrepTest 101, 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 top bun first: it is a broad, all-around claim. Then find the patty and ask what the evidence actually examined. Notice that the evidence looks at only one piece of the bigger thing the conclusion talks about. Pre-phrase the gap in your own words: clearing one part does not clear the whole. Then read the choices and keep the one that names that size jump. Eliminate choices that bring in new outside facts (Strangers) or that complain about a method the argument never relied on (Phantom Pieces).