No, Not Both, No One
Started by
Shirnel
· started 2020-03-04 05:49
· last activity 2020-03-20 15:33
· 5 replies
Can you please clearly explain this to me. I didn't understand this in the learning video and don't understand why Mehran negated the first premise i.e. P==>AB
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SamA
· 2020-03-04 20:47
Hello @Shirnel,
"No one who was promoted during the past year failed to attend the awards banquet."
This statement follows the format: No As are Bs.
When creating a sufficient and necessary diagram, we negate the second term.
If A, then not B.
A - - - - - - - -> not B
Let's apply it to this question.
No promoted person failed to attend.
If a person was promoted, that person did not fail to attend the banquet.
P - - - - - > not FAB
There is a double negative here, which I am guessing is what caused your confusion. Not failing to attend the banquet simply means attended the banquet. This is why we can say:
P - - - - - -> AB
Let's try one more example just to make this clear.
No cats can swim.
If it is a cat, then it cannot swim.
C - - - - -> not S
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Shirnel
· 2020-03-06 00:05
Thanks for this Sam
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Shirnel
· 2020-03-06 00:10
So basically with no, not both, no one and none, the same rule applies. Pick one make a sufficient condition (anyone), negate the other and make the necessary condition. So for the following:
No cats can swim.
This could be:
If it is a cat, then it cannot swim.
C - - - - -> not S
or it could be
If you can swim, then you are not a cat
S-----> not C
I just simply need to pick one, it doesn't matter which one it is?
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Shirnel
· 2020-03-06 00:36
Actually scrap the above, I just realized that the second is the contrapositive.
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BenMingov
· 2020-03-20 15:33
@Shirnel, exactly! Please let us know if you have any other questions.
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