Preptest 23, Sec. 3, 18 Forum

[gbpackerbacker]

It is a parallel. It just seemed really difficult. Could somebody explain the differenc between answer C (the correct answer) and say, answer E? I kind of feel that I am understanding it, but still have doubts. Thanks.

[matt@atlaslsat]

The short answer is simple but to see the logic behind is more complicated. The short answer is that the stimulus is a valid argument, so when we parallel it, we want the correct answer to be a valid argument (not just look similar). Answer choice (C) is a valid argument, while answer choice (E) is an invalid argument.

Let's take a look. The stimulus has an underlying argument core that looks like this

If Louie Armstrong + from 1989, then something impossible would happen. Since the impossible doesn't happen and the recording is definitely Louie Armstrong, the recording must not be from 1989.

IN ABSTRACTION

A + B --> something impossible

A is true, so B cannot be true.

(A) isn't employing the use of conditional logic and is therefore incorrect. Where's the "if...then..?"
(B) is is not a valid argument. It logic looks like the following

Properly Titled + from Berthe Morisot --> something impossible

Thus, is not Properly Titled.

The problem with this argument is that it could be properly titled but not be a painting from Berthe Morisot.

(C) is the correct answer. In logical form

17th Century + by Frida Kahlo --> something impossible

It is from the 17th Century, so it must not be by Frida Kahlo

(D) is an invalid argument, besides the fact that it's logical form is also different. Just because Käthe Kollwitz was known for prints does not mean that she was not both a painter and a sculptor.

(E) is also an invalid argument. This argument fails to establish that the portrait was not done by by Elisabeth Vigée-Lebrun. In more formal notation

Portrait + Acrylic --> not by Elisabeth Vigée-Lebrun

It is a Portrait, so it cannot be Acrylic

[gbpackerbacker]

Lots of help, Thanks!