Sufficient & Necessary Questions - - Question 19

Only an expert in some branch of psychology could understand why Patrick is behaving irrationally. But no expert is c...

Awolxo July 10, 2013

This question

Why did you take the contrapositive of the second premise and begin with that to make the transitive property?

Replies
Create a free account to read and take part in forum discussions.

Already have an account? log in

Naz July 11, 2013

So the principle in answer choice (E) is "If Charles is certain of being able to solve Patrick's behavioral problem, then Charles does no understand why Patrick is behaving in this way." We would diagram it: CSP - > not UP. To see if that principle can be validly drawn from the passage we must look at our own diagrams of the passage and see if we can connect "being certain of solving someone else's problem" to not understanding why Patrick behaves in the way he does.

The variable "CSP" is the sufficient condition in the contrapositive of the second principle rule. Therefore, we start there so we can connect "CSP" to "not UP." We see that the contrapositive is CSP - > not E. We can connect that to the contrapositive of the first principle rule through the transitive property to be: CSP - > not E - > not UP. Meaning: CSP - > not UP. Therefore, we can validly conclude the principle in answer choice (E) from the passage.

I hope that helps! Let me know if you have any more questions!

Advaith November 13, 2015

Thanks Naz