Either Mary or Alice will not come

[joham]

1) Either Mary or Alice will not come.
Is this sentence correct? What does it equal? Does it equal:

2) Neither Mary nor Alice will come. or
3) One of them, either Mary or Alice, will not come, but I don't know which. (Is there a simple way to express this idea?)

Many thanks.

 

[emsr2d2]

1) Either Mary or Alice will not come.
Is this sentence correct? What does it equal? Does it equal:

2) Neither Mary nor Alice will come. or
3) One of them, either Mary or Alice, will not come, but I don't know which. (Is there a simple way to express this idea?)

Many thanks.

It only means 3 to me. It's not the easiest idea to express! "Either Mary or Alice won't come" is the best way I can think of.

 

[5jj]

1) Either Mary or Alice will not come.
Is this sentence correct? What does it equal?

That's the sort of question that delights logicians, but, in practice, nobody would say those words except, possibly, in contexts where the meaning was very clear.

 

[joham]

Many thanks to emsr and 5jj. These are precious answers which I couldn't have got from any books.


Could you tell me how should we, if in practice nobody would say those words, express this complicated idea of 'One of them, either Mary or Alice, will not come and I don't know which'?

 

[5jj]

Could you tell me how should we, if in practice nobody would say those words, express this complicated idea of 'One of them, either Mary or Alice, will not come and I don't know which'?

As you have just done - I've coloured it red.

 

[SoothingDave]

"Either Mary or Alice will come, but not both."

It is strange to say who will not come when it is simpler and less confusing to say who will come.

 

[emsr2d2]

Interesting. I actually would use the original construction. If I have a friend who regularly fails to turn up to events then I would say "Alice [probably] won't come" if I invited her to a party. If I have 2 friends who regularly fail to turn up to events, but for some reason I think that on this occasion one of them will come but the other one won't, I would say "Either Mary or Alice won't come". It's true that it's probably not a very commonly needed construction but I don't see anything wrong with it. To my mind, it stresses their non-attendance rather than the attendance suggested in "Either Mary or Alice will come".