P: People who are red/green color-blind cannot distinguish between green and brown.P: Gerald cannot distinguish betwe...
gharibiannickApril 7, 2020
Clarification
So the stimulus says
A>notB
NotB
What is conclusion?
Since we know gerald is not B, and it is the necessary condition, we actually cannot conclude that he is A(red green color blind) because only the sufficient can bring about the necessary and therefore, we have no way to conclude anything
Is this the correct approach ?
Reply
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Your approach looks correct! Let’s take a look at this one for clarification. We start with a conditional premise.
R/G CB —> canNOT distinguish between green and brown CAN distinguish between green and brown —> NOT R/G CB
We are then told that Gerald cannot distinguish between green and brown.
Note that being able to distinguish between green and brown is our necessary condition (right side of the arrow). Because it’s not sufficient, it doesn’t then guarantee a necessary (or a sufficient, because that’s mistaken reversal), like a normal left to right conditional arrow indicates sufficient to necessary.
Because all we know is that Gerald cannot distinguish between green and brown (necessary), there is no relationship we can make deductions from. The arrow only goes left to right, not right to left. We would need the sufficient condition (left side) to be triggered in order to make valid deductions.
Hope this helps! Feel free to follow up if you have anymore questions.
