Logical Reasoning · Necessary Assumption

PrepTest 116 · Section 2 · Question 18

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

To prove a feature was not part of something from the start, you need at least one early version that lacked the feature.

The basic logic

The argument says a popular belief about what a thing always had is false, because the thing existed before the source that made the feature famous. Existing earlier is not enough. Find the plank that says at least one earlier version really did go without the feature.

Tiny words that decide it

“essential”
“long before”
“at least one”

Playground logic

Marcus says freeze tag's freeze rule was never a must-have, because kids played tag long before Owen's cousin's video made freezing famous. The patty is 'tag is older than the video.' The secret sauce: at least one of those older tag games had no freeze rule, or the old age proves nothing.

Step 2 · The kid story

The Freeze Rule Mystery

At recess, half the fourth grade believed tag had always come with a freeze rule. Why? Owen's cousin posted a hugely popular video of freeze tag, and now nobody could picture tag without freezing. Marcus put on his detective face. "Wrong!" he said. "Freezing is not a must-have part of tag. Kids were playing tag way before that video existed." Priya sipped her juice box. "Okay, but what if every one of those older tag games also had freezing? Then being older proves nothing." Marcus blinked. "Hmm. So I need at least one old tag game where nobody froze." Lulu wrote on her clipboard: older is not enough. One freeze-free game from before the video is the plank holding up your whole case. Pull it out, and Marcus falls in the puddle.

Step 3 · Try the model question

Many students think freezing is a must-have piece of tag, because a popular video made freeze tag famous. But this belief is mistaken: tag was played on playgrounds long before the video was posted.

The argument requires which assumption?

Step 4 · The courtroom tale

The Case of the Kite Tail

Mr. Whitfield snapped his suspenders. "Your Honor, the plaintiff claims every kite in this town must have a tail, because the famous kite festival poster shows tails. But kites flew here long before that poster." Judge Ambrose leaned forward. "Counselor, what if every one of those older kites had a tail too?" Mr. Whitfield paused. "Then my point about age means nothing. Fine. My case quietly depends on this: at least one kite before the poster flew without a tail." He called Grandpa, who swore he flew a tailless kite in his youth. The judge nodded. "Now your plank holds weight."

Step 5 · Work the real question

Open PrepTest 116, Section 2, Question 18 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion: a common belief about what a thing always included is false. Find the evidence: the thing existed before the source that popularized the feature. Ask what gap sits between 'older' and 'the feature was not essential.' Predict: at least one earlier version lacked the feature. Negate each choice and keep the one whose denial sinks the argument. Skip choices about other places or other features.