Some planning committee members—those representing the construction industry—have significant financial interests in ...
HeloPilotSeptember 28, 2019
Option A double negatives
Option A reads: No persons with significant financial interests in the planning committee's decisions are not in the construction industry.
Since it is a "no" statement, I would usually diagram this by negating the necessary side of the statement, hence:
P-->not CI with contrapositive CI-->not P
However, the construction industry is already negated in the sentence before being diagrammed. So would it be appropriate to diagram this as
P-->CI with contrapositive notCI-->notP in order to follow the rule of negating the necessary side? I always find these challenging when both sides of the sentence are negatives. Thanks
Replies
Create a free account to read and
take part in forum discussions.
The first sentence can be diagrammed as: PCM - some - FI. We know that some statements are reversible, so we can also say: FI - some - PCM.
The second sentence is trickier. I know that "No one who is on the planning committee lives in the suburbs" has the same meaning as "If you are on the planning committee, then you don't live in the suburbs," so it helps me to think of this latter sentence when I set up my diagram. It follows that the diagram is: PCM -> not S. The contrapositive of this is: S -> not PCM.
We have: FI - some - PCM PCM -> not S
Since we have an S->N statement and the Sufficient condition is shared, we can go ahead and make a deduction. This gives us:
FI - some - not S.
This is the diagram for answer choice (E), which reads "Some persons with significant financial interests in the planning committee's decisions do not live in the suburbs." So, (E) is the correct answer.
Answer (A) reads "No persons with significant financial interests in the planning committee's decisions are not in the construction industry." You're right- the double negatives here are meant to be tricky. However, we can reframe this using logic. We know that the double negatives cancel each other out and that the original sentence has the same meaning as the sentence "all persons with significant financial interests in the planning committee's decisions are in the construction industry." This is diagrammed as: FI -> CI. The contrapositive of this is: not CI -> not FI. Therefore, your second diagram is correct. Good work!
Does this make sense? Please reach out with any additional questions!
