PT19.S2.Q20 - anyone who insists that music videos are an art form

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http://7sage.com/lsat_explanations/lsat-19-section-2-question-20/
Can someone break this down? I thought B was the least attractive answer, and it turned out to be correct. I am completely clueless on this one; I can't even make heads or tails of the argument. Is it saying that since TV caused music videos to exist, then those that think music videos are art should also think TV gave rise to a type of art? But how is B anything like this? There is no causal indicators in B and there is no comparison in the original passage (like there is in .

c.janson35

This is a tricky question!

The argument is committing a very rare flaw and it is in presuming that someone knows something that is true, and can logically conclude something based on that statement. Let me give you an example because to hard to describe:

Billy thinks agrees that apples are fruits, so he should also be of the opinion that apples are sweet, since all fruits are sweet.

This looks like it is reasonable, right? But we are assuming that Billy is aware of the fact that all fruits are sweet in drawing our conclusion. What if Billy believes that all fruits are tart? Then he would be of the opinion that apples are tart. So, just because some sort of relationship exists doesn't mean that it is automatically and logically played out in a person's beliefs. We can't assume that they know of the relationship! And we similarly can't conclude that they are savvy enough to infer something from that relationship.

Now, back to the question...

What evidence do we have that everyone knows that television gave rise to music videos? We don't! Therefore we can't conclude that someone who thinks "MV--->AF" also believes that "T--->RAF" based on the fact that "T-->RMV".

This is best paralleled in choice B, and it makes even clearer this flaw. Anyone who thinks avocados are a fruit should also hold that pound cake is lower in fat than some fruit?? Whoa! That came out of no-where! Why did they say this thing about pound cake? "Since pound cake is lower in fat than avocados". Umm, I didn't know that? And I think avocados are a fruit! So how could I possibly hold the opinion that pound cake is lower in fat than some fruit? I couldn't. And that's the flaw.

Hope this helps! Let me know if you need me to break down the incorrect choices too!