Logical Reasoning · Flaw

PrepTest 118 · Section 3 · 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

Lots of people believing something is not proof that it is so.

The basic logic

The argument has a strict definition based on facts, but the only evidence is what people think. It jumps from 'most believe X' to 'X is true.' Name that move.

Tiny words that decide it

“in the opinion of”
“by definition”
“so”

Playground logic

Marcus's patty is that most kids think he's already the fastest runner. His definition says 'fastest' means winning more than half the races. His top bun: he is the fastest right now. That's the Everyone Says So flaw: what people believe got treated as the actual race results.

Step 2 · The kid story

Marcus, Fastest by Vote

Marcus started running laps every day after school. "I'm training to be the fastest kid in school." Then Nadia ran a poll. Seventy percent of the kids said Marcus was already the fastest. Marcus stopped mid-lap. "Well, the rule says whoever wins more than half the races is the fastest. So I'm the fastest now. I only have to keep winning like I am." Priya looked up from her juice box. "Marcus, how many races have you actually won?" Marcus paused. "I've... never counted." Lulu flipped her clipboard. "You won two out of nine. The poll only shows what kids believe." Marcus slowly started jogging again. Biscuit, who had won every race he ever entered, trotted past him.

Step 3 · Try the model question

Marcus is training hard to become the fastest runner in school. But in a poll, seventy percent of the kids said he already is the fastest. Since anyone who wins more than half the races is fastest by definition, Marcus is the fastest now and needs only to keep winning as he does.

Marcus's reasoning is open to which criticism?

Step 4 · The courtroom tale

The Case of the Most Popular Pie

At the county fair trial, the bakery claimed the 'Best-Selling Pie' ribbon. Mr. Whitfield read the rule: "Best-selling means more than half of all pies sold." The bakery's lawyer waved a paper. "Eighty percent of fairgoers told us our pie is the best seller!" Mr. Whitfield turned to the judge. "Your Honor, that shows what fairgoers believe. The rule counts pies sold. Where are the sales slips?" The lawyer shuffled. "We didn't keep any." The judge shook her head. "Many people thinking something is true does not make it true. Ribbon denied until someone counts."

Step 5 · Work the real question

Open PrepTest 118, Section 3, Question 13 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

First, notice the defined term and what fact the definition needs. Then check what evidence the argument actually gives. If the evidence is about what people think, say, or believe, while the conclusion is about what is true, you have the Everyone Says So flaw. Find the choice that names belief being taken as truth. Ignore choices describing moves the argument never makes.