English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. It only takes a minute to sign up.
Sign up to join this community
The prophesy made by Professor Trelawney about Harry Potter includes the phrase "Either must die at the hand of the other", speaking of Harry and Lord Voldemort.
Does this mean that both Voldemort must be killed by Harry and Harry must be killed by Voldemort?
Or merely that one must be killed by the other?
If the former, then presumably Harry is immortal after Voldemort's death.
As a pronoun, either has a meaning of "one or the other of two people or things" (Lexico). In the sentence, the contrast is between one of them and the other one: one must die at the hand of the other. Logically, this gives two mutually exclusive possibilities:
Once one of these possibilities happens, the prophecy is fulfilled: either has died at the hand of the other.
The alternative interpretation you give that requires both possibilities to be true would require a different initial pronoun, e.g. both:
Or better yet:
In math logic, A OR B statement can True in three cases:
(1) A is True and B is False
(2) B is True and A is False
(3) A and B is True
If “Either” means: one OR the other of two people or things, then "Either must die at the hand of the other" could be true in the case that both will die at the hand of each other. This is similar to the case (3) above. This prophecy admits a few ways of being fulfilled but in the HP series the third option is chosen.
