Quick question regarding Assumptions Forum

[dtubin]

Hi guys,

Quick question and down to the point. I'm having trouble with assumptions and picking out the right answer. I can usually get down to 2-3, but I've been using the LSATblog method of actually seeing the assumption.

Here is the link to the article: http://lsatblog.blogspot.com/2011/03/ar ... tions.html


Now, I'm confused because I'm finding it hard to get answers on certain nec/suf questions while using this method. Is it only to be used in some cases (if so, when?), or could it always be used? It is helpful on some questions, but I guess my process seems a little fucked.

Basically. I can get the core, premise and conclusion. Find the contrapositive...but then I'm stuck looking at the contrapositive? I guess I'm supposed to match the contrapositive to any similar answer choice? However, I'm skeptical of when it can be used...Insight is great. I'm going to ask my LSAT teacher the same question. Thanks guys.

[dtubin]

Ok, so I guess I can use this trick to "maybe" get the right answer "sometimes"?

But I should also use the negation trick with the original statement..

Ugh.

[bp shinners]

Are you using different methods for Sufficient and Necessary questions? It's important to distinguish the two from each other as well as other question types.

[barnum]

One of the problems with the article from the LSAT blog, is that he mischaracterizes the argument in the first place. Thus his idea about the assumptions is also faulty.

He is correct in saying that the answer choice can be stated as the contrapositive of the assumption, but the conditional aspect of the argument he presents is not stated in the argument and is the assumption in the first place.

This is why it is important to separate conclusions and premises. Let's take the argument - Fido is a dog. Therefore, Fido is a mammal.

The assumption would be that Dogs are Mammals and could be diagrammed D --> M. Although this may feel like that is what the argument stated, nowhere is it actually said that dogs are mammals, hence the idea that this is the assumption of the argument (albeit an obvious one). If we can agree that D --> M is the assumption, and we can agree that a contrapositive is a logical synonym for a conditional statement, then we could also say that the argument is assuming that anything that is not a mammal can't be a dog or
~M --> ~D. Although this may feel like an awkward construction, it would nonetheless hold as a viable answer choice.

So now to the arguments referenced on the blog. The first one has a premise that reptiles can't make changes to their behavior (~change). It then concludes they are not capable of complex thought (~capable complex). The argument does not present a connection between these two ideas and is therefore assuming a link exists (just like dog and mammal). So to get the assumption we simply add the arrow ~change --> ~capable complex. Now realizing that an assumption answer choice may be presented in the answer choices as the contrapositve, we are also prepared to look for capable complex --> change.

The second argument he presents is essentially the same.

Now as for being able to do this all the time. No you will not be able to do this for all assumption questions. But when I take a test, I look for these first. If it is among the answer choices, then happy day...I am done, but if not, I realize that arguments can have lots of assumptions and I have to move on to some other technique.