LSAT 154 | Section 1 | Logical Reasoning: Q9

QUESTION TEXT: Gecko lizards are found in any environment where there…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: The climate here isn’t wet.

REASONING:

gnats ➞ wet AND geckos
There are no geckos here.

ANALYSIS: This argument correctly concludes there are no gnats. This can be done with the contrapositive of the statement above:

geckos OR wet ➞ gnats

It’s an “or” statement. So having either sufficient condition means the necessary condition is also true. There is, however, no linkage between the two conditions in an “or” statement!

Like, suppose I say “If you are an LSAT student or a criminal, you are breathing”. And then I say you’re an LSAT student. That doesn’t…..make you a criminal! But, that’s what this argument is doing by combining the two conditions in the “or” statement.

I normally say there’s no need to draw flaw questions, but I think it’s worth drawing this one. You have to figure out what the author is assuming. We know they correctly say: “geckos ➞ gnats” and they conclude “wet“. So this is a bit like a sufficient assumption question: put the premise and conclusion together and spot the gap:

geckos ➞ gnats wet

So the author is assuming “gnats ➞ wet“, with the contrapositive “wet ➞ gnats”. This very last one is the correct answer. Phew, that’s a lot of diagramming. This is a novel approach for a flaw question, it really is more like a sufficient assumption question in structure.

___________

1. The author correctly understood the relationship between geckos and gnats. They said no geckos ➞ no gnats. This is 100% correct and not a flaw.This answer has it backwards and says no gnats ➞ no geckos. This is not what the author did: their sub conclusion that there are no gnats is correct.
2. CORRECT. See the analysis above. The author got the relationship between gnats and wetness backwards.
3. The author did consider this: they said it’s wrong. The author said gnats can only survive with geckos.
4. The author never actually even said if geckos eat gnats. It just said they exist in the same environment. This answer is way off base.
5. The author was clear that gnats cannot survive if they aren’t in a wet climate. So they more or less did establish this: their conditional statement contradicts this answer. (We have to generally assume authors’ conditional statements are true).

Recap: The question begins with “Gecko lizards are found in any environment where there”. It is a Flawed Reasoning question. Learn how to master LSAT Flaw questions on the LSAT Logical Reasoning question types page.

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