“Neither can live while the other survives”— does it make logical sense?

Question

At the end of the fifth book of Harry Potter, "The Order of Phoenix", there is a prophecy concerning Harry Potter and Lord Voldemort:

The one with the power to vanquish the Dark Lord ( Lord Voldemort) approaches ... born to those who have thrice defied him ( that's Harry Potter), born as the seventh month dies ... and the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not ... and either must die at the hand of the other for neither can live while the other survives ... the one with the power to vanquish the Dark Lord will be born as the seventh month dies ...

I am confused over the phrase

neither can live while the other survives

What does it mean? Does it mean anything? On the surface it seems it does. But upon further thinking this phrase is self-contradictory. If neither Potter nor Voldemort lives, then by logical deduction, the second phrase "while the other survives" is certainly false. Similarly, if either Harry Potter or Lord Voldemort survives, than it follows that the first phrase "neither can live" is logically false.

Juxtaposing two contradictory statements together in a single phrase makes the phrase completely meaningless. It's like saying "I am A, but I am not A"-- is this phrase true or false, or neither true nor false? Similarly, "neither can live while the other survives" can this phrase be true, or false, or can neither be true nor false?

Do I miss anything? Harry Potter's author JK Rowling's English is subtle indeed!

Answer 1

You're correct, it is indeed contradictory. Taken purely logically, then if neither can live while the other survives, then if Harry is alive Voldemort must be dead and if Voldemort is alive Harry must be dead. Since we know both Harry and Voldemort are alive, the statement is clearly false. Since the statement is part of a piece that refers to them as alive, and one killing the other, then the passage as a whole is clearly illogical.

However, there are a few sensible ways to read it.

One is to suggest that their life under this doom (in both the common sense, and the original sense of being fated to something) is incomplete. Neither truly live until after it comes to pass.

The other, is that as a prophesy it is speaking about the future, so even though the present tense is used, it should be thought about in terms of the future. This is an unusual use of tenses for most cases, but reasonable if we consider that we're talking about a magical trance that leads people to speak dialogue in a completely different register and rhythm than that the author normally uses! And this also makes it make perfect sense; some point in the future will come, in which one of them must be dead in order for the other one to survive.

Spoiler: Hover over the text to read it if you have read the end of the last book, or don't care about the plot being given away:

It also has a different interpretation, that becomes clear later. Voldemort is in a state that is neither life nor death, and for that reason cannot be killed. This state can only be ended when certain objects are destroyed, and Harry is one of those objects. This means that while Harry survives, Voldemort cannot truly live, and cannot truly die. Harry dies, and comes back to life. Harry's death is the destruction of the last object that keeps Voldemort in his non-life/non-death state, so Voldemort truly lives when Harry stops surviving. Then they can kill him.

The strangeness is justified as fitting with the general strangeness and cryptic opacity of the prophesy as a whole (again, especially in taking how it doesn't fit with the normal style of the books). It's justified further in light of the plot twist above.

It's also deliberately strange in its phrasing, because you're meant to be wondering about it until you've read on through the series.