No small countries and no countries in the southern hemisphere have permanent seats on the United Nations Security Co...

shamadi August 11, 2020

In verse of first sentence

Hello, Why is it that the first sentence has to be reversed as in why cant we say /SC----> Have permanent seats? why do we say SC----> /have permanent seats? /SH-----> have permanent seats ?

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shunhe August 11, 2020

Hi @shamadi,

Thanks for the question! So if I understand your question correctly, it’s why we diagram that sentence as

Small country v Country in southern hemisphere —> ~Permanent seats on the UNSC

as opposed to

~Small country & ~ Country in southern hemisphere —> Permanent seats on the UNSC

So to start of, those are both mistaken negations of each other, so they can’t both mean the sentence. Remember, X —> Y and ~X —> ~Y don’t mean the same thing. For example, saying that if it’s dinner time, I’ll eat some food doesn’t mean that if it’s not dinner time, I won’t eat food.

So now we reach the question of how to diagram “No X are Y” statements. And the answer, as you now know, is X -> ~Y. And this actually matches our intuitions about how we use these statements in the real world. Let’s take the following statement:

No turtles are mammals.

What’s this mean? It means that if something’s a turtle, it’s not a mammal. And that’s just

Turtle —> ~Mammal

Contrast that with

~Turtle —> Mammal

Which means that if something’s not a turtle, it’s a mammal. Is that what “no turtles are mammals” means? No. And that’s why we diagram this statement, which is a “no X are Y” statement, the way we did.

Hope this helps! Feel free to ask any other questions that you might have.