Unplugged Practice Test: Logical Reasoning Set 2, Question 9 (Flaw)
Taking the test? Finish it first. This page shows the answer.
- Flaw questions ask you to name the reasoning error the argument commits, not to judge whether its conclusion is true.
- Before you read the choices, describe the argument's error in your own words. Most Flaw questions reward 1 of a small set of recurring patterns, so naming the pattern first keeps the trap answers from sounding right.
- Every question on this test is original, written to the same logical skeletons as real questions, and Steve checked every one himself before release.
The question
Advertisement: Thornridge exterior house paint is made with a titanium-based pigment. Coatings chemists agree that titanium-based pigments are among the most durable materials available, far more durable than the pigments used in ordinary house paints. So most houses would hold their color longer if they were painted with Thornridge.
9. The advertisement's argument is most open to criticism on the ground that it
- (A)handles a quality that would be enough to make a paint durable as though no paint could be durable without it
- (B)shifts between two unrelated senses of the term "durable" as the argument proceeds
- (C)supports its conclusion with a premise that could be accepted only by someone who already accepted the conclusion
- (D)assumes that a product as a whole carries a quality on the ground that a single component of the product carries it
- (E)concludes that a product produces a result merely because the product is widely used by those who obtain that result
DWhy (D) is correct
The ad reasons that Thornridge would help most houses hold color longer because it's made with a titanium-based pigment, and coatings chemists rate titanium-based pigments as far more durable than the pigments in ordinary paint. That's a leap from one ingredient being durable to the whole can being durable. It ignores everything else the paint contains, binders, solvents, other pigments, that could affect how long a house holds its color. Whether the finished product performs like its most durable component is exactly what's unestablished, which is (D)'s move.
Why the other answers are wrong
AWhy (A) is wrong
(A) doesn't fit: the ad never treats pigment durability as necessary for a paint to be durable, it only claims one ingredient's durability.
BWhy (B) is wrong
(B) fails because durable carries one meaning throughout the ad.
CWhy (C) is wrong
(C) doesn't fit: the premise concerns titanium pigments, not the paint's overall color-holding, so nothing here presupposes the conclusion.
EWhy (E) is wrong
(E) misses the ad's reasoning, which runs from the pigment's durability, not from usage, and never claims Thornridge is popular among people who kept their color.
Common questions
What type of question is this?
Flaw. Flaw questions ask you to name the reasoning error the argument commits, not to judge whether its conclusion is true.
How do I get better at Flaw questions?
Before you read the choices, describe the argument's error in your own words. Most Flaw questions reward 1 of a small set of recurring patterns, so naming the pattern first keeps the trap answers from sounding right. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
