December 2004 LSAT Section 2 Question 20

Although the geological record contains some hints of major meteor impacts preceding mass extinctions, there were man...

SorooshKosha on December 29, 2019

Difference Between A and B

Hello, I was able to narrow down the answer choices to A and B, and did select the correct answer. Although I do understand why choice A is correct, I still cannot completely grasp why B is incorrect. I have read over Naz's explanation (it was great), but I would truly appreciate a breakdown of B and how it cannot be the answer. Thank you in advance!

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SamA on January 8, 2020

Hello @SorooshKosha,

Good question! This is a strengthen w/ sufficient premise question, which means we need to guarantee that the conclusion is correct. In other words, we need an assumption that, if true, shows that there cannot be a consistent causal link.

From the stimulus, we know that there are "some hints of major meteor impacts preceding mass extinctions."

B gives us the following sufficient/necessary statement.
If there is a consistent causal link (CCL), then many mass extinctions have followed major meteor impacts (MME).

CCL - - - - - - - - > MME
not MME - - - - - - -> not CCL

If we knew that there were not many mass extinctions following major impacts, then the conclusion would be properly drawn! Here is the problem. They want us to think that "some hints" means that there weren't "many" mass extinctions. However, these terms are not mutually exclusive. "Many" is a very subjective word, and in the LSAT world, we have to treat it the same as "some."

The first sentence of the stimulus absolutely allows for the possibility that there were many mass extinctions. Which means, we cannot use the (not MME - - - -> not CCL) logic of answer choice B to guarantee the conclusion. B leaves room for the possibility that there is a consistent causal link. On a strengthen w/ sufficient question, we have to eliminate every doubt that the conclusion is correct.

SorooshKosha on January 10, 2020

Thanks!

Anthony-Resendes on September 15, 2020

So for all sufficient and necessary condition type questions would you suggest diagramming all of them?