Logical Reasoning · Necessary Assumption

PrepTest 145 · Section 2 · Question 3

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

If you claim a hidden condition sits under a problem, you must assume that condition actually makes the problem more likely.

The basic logic

The argument points to visible causes, then says a deeper condition is also at work, and its evidence only shows the condition exists. The required link: that condition makes the group more vulnerable to the visible troubles.

Tiny words that decide it

“whichever”
“underlying”
“also”

Playground logic

Kevin blames the team's losing streak on rain, injuries and tough opponents, then says the real hidden problem is that they practice only one play. His patty proves the one-play habit exists, but the secret sauce must be that having only one play makes a team easier to knock down.

Step 2 · The kid story

Kevin's One-Play Problem

Kevin's soccer team, the Pineapple Rexes, has lost six games in a row. The coach blames muddy fields, a sprained ankle, and a really good team from across town. Kevin, mid-dinosaur-fact, interrupted himself. "Sure, whichever one you pick, that's the thing that happened that day. But underneath it all is the real problem. For two years we have practiced only one play: the Big Stomp. Every practice. Only the Big Stomp." Lulu wrote on her clipboard. "Okay, you showed you only know one play. But for that to be the hidden problem, knowing only one play has to make you easier to beat when the mud or injuries or tough teams show up." Kevin blinked. "Right. Like a T. rex with only one move. Every meteor gets you."

Step 3 · Try the model question

Kevin: Our team's losses have been blamed on mud, injuries and strong opponents. Whichever of these caused each loss, there is likely also a deeper problem: for two years we have practiced only one play.

Kevin's argument requires which one of the following assumptions?

Step 4 · The courtroom tale

The Case of the One-Recipe Restaurant

"Your Honor," said the prosecutor, "the diner closed because of a broken oven, a snowstorm, and a new rival across the street." Mr. Whitfield stood. "Any of those may explain a bad week. But beneath them sits a deeper cause: for ten years the owner served exactly one dish." The judge leaned in. "Counselor, you have proven the menu was short. For it to be a cause, you need one more piece." Whitfield nodded. "Yes, Your Honor. A one-dish menu must leave a diner more exposed when ovens break, storms hit, or rivals open." "Then argue that link," said the judge, "because without it your deeper cause is just a fun fact."

Step 5 · Work the real question

Open PrepTest 145, Section 2, Question 3 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Separate the visible causes the argument accepts from the deeper condition it adds. Notice that the evidence only shows the deeper condition exists. Ask what bridge links that condition to the trouble. Use the Pull the Plank test on each answer: negate it and see if the deeper-cause claim collapses. Discard answers that compare to an outside group, predict the future, or deny the visible causes.