Presupposes that which is to be proved

[willyhud]

I'm having trouble ruling out this answer choice and its many variants, such as:

-presupposes what it sets out to demonstrate
-assumes what it sets out to conclude

I believe the PS LR Bible mentions that this is often a wrong choice, which is helpful, but when I attack problems with this answer choice, I invariably find myself not ruling it out and instead just seeing if there's a better contender. I'd like to get to the point where I can see it and eliminate it on sight when it's wrong.

I think part of the problem is that it seems like a very broad, catch-all flaw in reasoning. If you're not reasoning properly, then you're assuming what you set out to conclude.

I know the test makers must mean something much more specific with this option...?

[Jon Denning]

Hey Willy - thanks for the question (it's a good one!). The answer choices you've given, and thus the flaw you're describing, is one called circular reasoning, and it's undoubtedly one of the trickiest ideas to come up in argumentation on this test. The good news is that when it happens it's usually pretty easy to spot (even if the underlying problem with it isn't apparent). Basically what happens is that in stating a conclusion, the author uses as support for that conclusion the exact same idea. In other words, it's just a restatement. So pretend I say something like "I believe that chocolate cake is the best kind of cake." And someone says "Why?" And the answer I give is "Well because it's better than the other kinds." I haven't given any reason to agree with my belief; I've only said what it is that I believe a second time. That's circularity.

To spot it just watch for a conclusion that has the exact same idea given as its premise. If you don't see that happen, then it's a different type of flaw, and the answer choices below are merely traps (and they're common traps, because, as you point out, they seem broad enough to possibly work). Circular reasoning sounds broad, but it is VERY specific and with some continued practice you'll get very good at spotting it.

Jon