Logical Reasoning · Flaw

PrepTest 136 · Section 2 · Question 11

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

The argument treats a change in what we know about something as if it were a change in the thing itself.

The basic logic

Evidence: we recently learned there are more of something than we thought. Conclusion: so a claim that the real number is going down must be wrong. But discovering what already exists says nothing about whether the actual amount is shrinking. Learning and losing can both happen.

Tiny words that decide it

“we know”
“it is”
“so”

Playground logic

Marcus learns there are more crayons in the art closet than anyone knew, and declares that Sharon's 'crayons are disappearing' claim is busted. The patty is about our count; the top bun is about the real crayons. That's a Scope Shift from knowing to being.

Step 2 · The kid story

The Great Crayon Count

Sharon told the class, "Crayons are getting snapped and lost every single week!" Marcus didn't buy it. On Monday, Ms. Rivera found a dusty box of crayons behind the paint jars. Nobody knew it was there. Marcus climbed onto a chair. "Aha! There are way more crayons than we thought! So Sharon is definitely wrong. Crayons aren't disappearing!" Lulu tapped her clipboard. "Marcus, the box was always there. We just didn't know about it. Finding it changes our count, not the crayons." Frankie, for once, agreed with Sharon. "Crayons could still be snapping every week. We'd just be losing them from a bigger pile than we realized." Priya nodded. "Learning something new about the pile isn't the same as the pile changing." Marcus slowly climbed down from the chair.

Step 3 · Try the model question

Ms. Rivera recently found a hidden box, so there are more crayons in the room than anyone knew. This definitely disproves Sharon's claim that crayons are being lost each week.

What is the main mistake in Marcus's reasoning?

Step 4 · The courtroom tale

The Case of the Missing Marbles

The Marble Club accused the toy shop of losing marbles from its display jar every month. Shop lawyer Dexter Pine stood up grinning. "Your Honor, last week we found a second jar of marbles in the back room. We had no idea! We have far more marbles than anyone knew. So clearly no marbles are being lost." Mr. Whitfield tugged his suspenders. "Your Honor, that second jar didn't appear by magic. It was always there. Mr. Pine has changed what he knows, not what he has. Marbles can still roll out the door each month." Judge Lin nodded. "Discovering a pile isn't the same as the pile growing. Objection noted, Mr. Pine."

Step 5 · Work the real question

Open PrepTest 136, Section 2, Question 11 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Separate the evidence from the conclusion and ask what each is really about. Is the evidence about what people have found out, while the conclusion is about what is actually happening in the world? If so, the argument slides from knowledge to reality. Describe that slide in your own words, then look for the choice that names a confusion between those two things. Skip choices naming classic flaws that the argument doesn't actually commit.