Logical Reasoning · Flaw

PrepTest 149 · Section 3 · Question 2

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

Something being useful for a job does not show it was made for that job.

The basic logic

The argument shows that an activity needs a certain tool and that some tool fits the need. Then it jumps to: the tool probably came about mainly to serve that activity. Spot the leap from 'it serves a purpose' to 'it was created for that purpose.'

Tiny words that decide it

“therefore”
“likely”
“primarily”

Playground logic

Kevin's patty: pillow forts need teamwork, teamwork needs a shared supply spot, and Grandpa's big closet is a shared supply spot. His top bun: Grandpa built the closet mainly for pillow forts. Fitting a job is not the same as being built for it.

Step 2 · The kid story

Kevin Solves the Closet Mystery

Kevin had a theory, and as usual it started with dinosaurs and ended somewhere else. "Building a pillow fort is a team job," he said. "Team jobs need a place where everyone can grab supplies. Grandpa's giant hall closet is full of blankets and pillows that anybody can grab. So Grandpa probably built that closet mainly for pillow forts." Grandpa looked up from his crossword. "I built that closet in 1985. For winter coats." "But it works great for forts!" "So does the couch," said Grandpa. "I did not buy the couch for forts either." Lulu wrote: Useful for it is not the same as made for it. Kevin nodded slowly, then asked if the couch was made for pineapple pizza.

Step 3 · Try the model question

Kevin: Building a pillow fort is a team job, and team jobs require a shared spot for supplies. Grandpa's big closet is exactly such a shared spot. So Grandpa most likely built the closet mainly to help with pillow forts.

Kevin's reasoning is flawed because it

Step 4 · The courtroom tale

The Case of the Handy Hammock

The prosecutor pointed at the tree house. Your Honor, napping in a tree takes a safe place to lie down. A hammock is such a place. Therefore the defendant clearly hung that hammock mainly so he could nap on duty. Mr. Whitfield tugged his suspenders. My client hung it to store the soccer balls. That it makes a fine bed proves only that it makes a fine bed. A spoon can scratch your back, and nobody thinks spoons were invented for itchy backs. The judge chuckled. The prosecution has shown a use, not a purpose. Case dismissed. Also, I want that hammock.

Step 5 · Work the real question

Open PrepTest 149, Section 3, Question 2 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Locate the conclusion and its key word about origin or purpose (why something came to be). Then check what the premises really show: only that the thing is useful for some job. Name the gap in your own words before reading the choices: useful for does not mean made for. Choose the description of that gap. Cross off descriptions of moves the argument never makes.