The author uses the word "immediacy" (line 39) most likely in order to express

on March 25 at 12:31AM

Contrapositive

Dear Mehran: Once we reverse and negate our conditional statement into a contrapositive, how will we know or apply it to the answer choices. A perfect example is when we have an inference or must be true question, after we reverse our conditional statement how do we know which answer chioce is correct?

3 Replies

Shunhe on March 25 at 12:51PM

Hi @emarsal,

Thanks for the question! Generally speaking, when we take the contrapositive of our conditional statements, we are doing so because we see that doing so will help the pieces of the logical chain fit together, and so that’s how we’ll know it applies to the answer choices. For example, take a question that asks for the necessary assumption:

~B
A —> B
Conclusion: C

We see here that if we take the contrapositive of the conditional in the second line, we can get something with a ~B term in it that we can use. So then we’ll have:

~B
~B —> ~A

From which we can conclude

~A

And then if an answer choice tells us that the argument needs to assume ~A —> ~C (or equivalently, C —> A), then we know that that answer choice is correct. All we really have to do here is follow the logical flow.

Hope this helps! Feel free to ask any further questions that you might have. If you have any specific examples in mind, feel free to ask about those as well.

on March 30 at 03:03AM

Yes it does a great deal. I have another question though, how generally do we know which logical reasoning questions that the contrapositive will be the correct answer choice? Is it only the Must be true questions? Lastly, what particular order do you reccomend answering the logical reasoning questions? If we ar using the computer, we wont be able to switch around like paper an pencil.

Shunhe on April 7 at 04:18PM

Hi @emarsal, contrapositive can show up in a number of different question types, so just generally keep an eye out for them in the way I described above. What matters in the end is that the contrapositive fits within the flow of the logic. Generally speaking, I would just recommend working on the logical reasoning questions from beginning to end, unless there was one that was really stumping you for some reason. There's not really any huge benefits to jumping around from my experience.