LR Problem Set #1, Q: 57

[moshei24]

Hi!

I don't see why the reasoning in this question is flawed. Can you please explain to me why it is? If they didn't come in through ground level or anywhere above, wouldn't they have to have come in below ground level? Or is it flawed because they could've already been in there? Please clarify.

Thank you!

[Joshua Kronick]

I believe the issue is that just because someone claims X or Y didn't happen doesn't prove that Z happened instead. That seems to mirror the stimulus and the correct answer choice. In the stimulus the guard maintains that they didn't enter at or above ground level, so therefore the stimulus concludes they must have entered below. This is the same as B where the competitors claim that the shirts weren't sold at a profit or break even so the lsat concludes it must have been sold at a loss.

[moshei24]

So because the stimulus didn't say that there were only three possibilities, that's the flaw? You can't assume Z unless X, Y, and Z are the only options, which wasn't explicitly stated in the question?

Thanks!

[Joshua Kronick]

I believe the issue is just because someone says X and Y didn't happen doesn't mean Z had to happen. How can we know positively that just because he claims it to be that way, that in fact it is that way? That is what I believe the issue is here. Also note how the correct answer choice mirrors that flaw with the competitors claiming something didn't happen and then a conclusion is made after that Z MUST have happened therefore.

[Adam Tyson]

Actually, the flaw here really has nothing to do with the number of possibilities. Rather, it's about an unwarranted assumption - that the security guard is correct! Just because he SAYS they didn't get in from ground level or above doesn't mean that they didn't. He could be mistaken, or lying, right?

That's why answer B parallels the stimulus - just because the store SAYS they neither made profit nor broke even doesn't mean it's true, since they could be mistaken or lying, so it's wrong to conclude that the third possibility must be true.

Adma M. Tyson
PowerScore LSAT Instructor

[moshei24]

Makes sense.

Thank you!