Logical Reasoning · Necessary Assumption

PrepTest 116 · Section 3 · 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

Necessary Assumption

The one idea it tests

An old reason for a rule is gone, so the arguer says to drop the rule. That only works if dropping it actually helps the new goal.

The basic logic

Find the top bun (get rid of the thing). Find the patty (the old reason is gone, now we can pick what is best for a new group). The gap: nobody showed the change is better for that group. Pull the Plank on each choice.

Tiny words that decide it

“so”
“therefore”
“should”
“because”

Playground logic

Tommy's patty says the rest stops on Biscuit's walks were made for Grandpa's old dog, and that dog is gone, so now the walks can suit Biscuit. His top bun says to cut the rest stops. The secret sauce: walks with no rest stops really are better for Biscuit.

Step 2 · The kid story

Biscuit and the Bench Stops

Every walk with Biscuit has three long bench stops. Tommy asked why. Grandpa explained: years ago his old dog, Pepper, had stiff knees and needed to sit down a lot. So the family always stopped at every bench. "But Pepper isn't here anymore," Tommy said. "Now we can plan walks that are good for Biscuit. So, no more bench stops!" Lulu tapped her clipboard. "Wait. You only told me why the stops started. You never told me Biscuit is better off without them." Biscuit, meanwhile, was flopped on the grass, panting. Priya sipped her juice box. "Pull the plank, Tommy. If walks without stops are NOT better for Biscuit, your whole plan falls into the creek." Tommy looked at the panting dog. "Okay. Maybe I need to check that part."

Step 3 · Try the model question

Tommy: Our dog walks include long bench stops only because Grandpa's old dog needed rest. That dog is gone, so we can now plan walks that are good for Biscuit. Therefore, we should drop the bench stops.

Tommy's reasoning requires which one of the following assumptions?

Step 4 · The courtroom tale

The Case of the Midday Bell

In a small town, a factory bell rang at noon so workers would know to eat. The factory closed long ago. Mr. Whitfield, thumbs in his suspenders, argued: "The reason for the bell is gone. Now we can do what suits today's neighbors. So, Your Honor, silence the bell." Judge Okafor raised an eyebrow. "Counselor, you told me why the bell began. Where is your proof that the neighbors are better off without it? If some of them love that noon chime, your argument has a hole." Mr. Whitfield coughed. "I shall bring a survey, Your Honor." The lesson: an outdated reason opens the door to change. It does not prove the change is an improvement.

Step 5 · Work the real question

Open PrepTest 116, Section 3, Question 1 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Mark the conclusion: a recommendation to remove something. Mark the support: the original reason no longer applies, and the arguer says we can now aim at a new group's benefit. Ask what must be true for removal to serve that group. Predict: the version without the thing is better for that group. Pull the plank on each choice; the right one, negated, wrecks the argument. Skip choices that bring in new effects or talk about the old reason's group.