Exercise 2.5 - Answers


(i) Yes. (Of course it cannot be true that he both will and won't. But that does not mean that the first sentence means that it isn't true that he both will and won't.)

No. The first sentence will be false, but the second true, if he comes both days. (Does this mean that the "or" is exclusive here? No! The presence of "but not both" is enough to make the sentence as a whole exclusive. But the "or" could perfectly well be inclusive. So one could translate the whole as "[[John will come today John will come tomorrow] [John will come today John will come tomorrow]]".

Yes. It is correct to treat this as equivalent to an inclusive "or". To treat it as exclusive would be to take it as meaning the same as "You won't win unless you try, in which case you will win." Though perhaps in some cases it may be implied that, if you try, you will win, even in those case this will surely be a matter of implicature, rather than of logical implication.

It depends. If the first sentence means the same as "He is president of the United States; that is, the most powerful man in the world." the translation will not do. For then, if he were the most powerful man in the world, but not president of the United States, the second sentence would be true, but the first false.

No (probably). If you may have soup but not fish, the first sentence (as most commonly used) will be false but the second true.



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