Logical Reasoning · Flaw

PrepTest 155 · Section 2 · 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

Flaw

The one idea it tests

Who gained from an event is treated as proof of who caused it.

The basic logic

The argument says a group benefited after something happened, so the group made it happen. But you can profit from rain without making clouds. Benefit is not cause; this is a cousin of the Rooster.

Tiny words that decide it

“shown by”
“after”
“result of”

Playground logic

When the school ran out of pencils, Tommy's eraser-and-pencil stand earned a fortune, so Marcus claims Tommy hid the pencils. Tommy's profits are the patty, 'Tommy caused the shortage' is the top bun, and the secret sauce is that whoever benefits must be the cause.

Step 2 · The kid story

The Great Pencil Shortage

One Monday every pencil cup in school was empty. Kids panicked. By Friday, Tommy's little desk stand had sold forty pencils and his pockets jingled. Marcus slammed his notebook shut. "Case closed! Tommy made the shortage happen. Look how much money he made after it started!" Tommy squeaked, "I just had a box from Grandpa!" Lulu tapped her clipboard. "Marcus, the delivery truck got stuck in snow. Ms. Rivera said so." Marcus waved her off. "Then why is Tommy rich?" Priya sipped her juice box. "Because when something runs short, whoever still has some does well. Getting lucky after an event is not the same as causing it. The umbrella seller did not make it rain."

Step 3 · Try the model question

Marcus: The pencil shortage at school was not caused by a late delivery. Tommy planned it so he could sell pencils at his desk stand. We know this because, after the shortage began, Tommy earned much more money than before.

Which one of the following points out a flaw in Marcus's reasoning?

Step 4 · The courtroom tale

The Snowplow Conspiracy

A town council accused a snowplow company of causing a blizzard. "Your Honor," said the council's lawyer, "after the storm, this company's earnings tripled. Who else would want a blizzard?" Mr. Whitfield hooked his thumbs in his suspenders. "Your Honor, the hot cocoa stand also had its best week ever. Shall we arrest the cocoa?" Laughter. "My clients earned money because it snowed. That does not mean it snowed because of my clients. Earning from an event and making the event are two different things." The judge sighed. "Unless the plow company owns a weather machine, this case is dismissed."

Step 5 · Work the real question

Open PrepTest 155, Section 2, Question 13 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion: some party deliberately brought an event about. Find the evidence: that party did well after the event. Ask: could they have done well without causing it? If yes, that is the hole. Choose the answer that says the argument ignores that benefiting from an event is different from bringing it about. Test each other answer: does the argument really make that move? If not, cross it out.