• Nathan Fox

Sufficient-Necessary Flaw

Test 2 - Section 2 - Question 11

Logical Reasoning Difficulty: 5


If you understand the difference between sufficient and necessary, and you spot the politician's sufficient-necessary flaw, you can make quick work of this question.

We're asked to choose an answer that's consistent with the biologist's statement, but violates the politician's statement. I immediately said "deforestation stops but the koala dies anyway." That turns out to be the correct answer.

This is simply pointing out the politician's sufficient-necessary flaw. The biologist said "hey, deforestation is going to kill the koala for sure." The politician said "oh, so all we need to do is stop deforestation and the koala will live forever!" which is stupid, because there might be a bazillion other ways the koala could die. Climate change, koala hunting, poison in their water—maybe koalas, like pandas, could stop having sex with each other and die off due to lack of procreation. We just don't know. The politician has made the LSAT's most common flaw, which B perfectly describes. And which you might have predicted, if you'd thought for a moment before jumping into the answer choices.

A) This is consistent with both speakers' statements.

B) Yep. This is consistent with the biologist's statement but violates the politician's statement.

C) Reforestation? Neither speaker even mentioned reforestation. So this statement is "consistent with" both speakers' statements.

D) Neither speaker mentioned what would happen if deforestation slowed. 

E) Neither speaker mentioned what would happen if deforestation slowed.

The biologist would probably agree with B—and anyway, it definitely does not violate the biologist's statement. But B definitely violates the politician's misunderstanding. So B is the answer.

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