WARNING: spoilers below
As a whole, things are as they seem. Because of the jet engine from another timeline/universe crashing through (the original cause is never explained) their universe is going to collapse. I believe this is because there is no appropriate 'cause' to lead up to this effect.
Before I get started, let me say that the director's cut is also clear that the people he affected most during the 'collapsing time period' will remember some things that happened. That's why they wake up after he dies.
There appears to be a higher power that's trying to prevent the universe from collapsing. Donnie has the correct sort of mind to not only see the divine messenger (the rabbit), but is also willing to act on those messages.
What the universe needs is for Donnie to use his mental powers, that develop through the movie (allowing him to see potential paths through time) to move himself and the jet engine backwards through time. Unfortunately, this will kill him. The higher power needs to convince Donnie to do it anyway. He does, erasing everything that happened, BUT brought the universe the needed 'cause' in order to prevent reality from collapsing. This is hinted at through the old woman waiting for the letter. Donnie needs to be the one to send the letter, just as he needs to send the jet engine.
Now, what the director's cut shows is a lot of this is explained in the book he reads, the philosophy of time travel. It reveals that this sequence of events has happened several times before, and always ends with a person somehow causing their own deaths. One example is a man who makes an arrow, and is shot by the same arrow, but there's no shooter. He was the shooter, in the other timeline.
What's just a important is Donnie knows this. Donnie knows that in order to end this, he has to die. One of the reasons he laughs at the end is because he realized the higher power, sending him messages to follow, was setting him up. Not only do his actions lead to multiple people dying, they also show him that the world is genuinely better off without him. Everyone is happier.
His sister and mom won't be in the plane that explodes because they'll be grieving for him, and his sister won't be able to compete. Since his sister won't compete, the Asian girl will win the talent contest. The flood and arson won't happen, so the teacher won't lose her job. The self help guru will understand how wrong and terrible his addiction is, and hopefully get help and change. The psychiatrist will realize that not all people who have visions are crazy. Two innocent people will live.
And that's it, really. The higher power...well... they made him do it.
As a whole, things are as they seem. Because of the jet engine from another timeline/universe crashing through (the original cause is never explained) their universe is going to collapse. I believe this is because there is no appropriate 'cause' to lead up to this effect.
Before I get started, let me say that the director's cut is also clear that the people he affected most during the 'collapsing time period' will remember some things that happened. That's why they wake up after he dies.
There appears to be a higher power that's trying to prevent the universe from collapsing. Donnie has the correct sort of mind to not only see the divine messenger (the rabbit), but is also willing to act on those messages.
What the universe needs is for Donnie to use his mental powers, that develop through the movie (allowing him to see potential paths through time) to move himself and the jet engine backwards through time. Unfortunately, this will kill him. The higher power needs to convince Donnie to do it anyway. He does, erasing everything that happened, BUT brought the universe the needed 'cause' in order to prevent reality from collapsing. This is hinted at through the old woman waiting for the letter. Donnie needs to be the one to send the letter, just as he needs to send the jet engine.
Now, what the director's cut shows is a lot of this is explained in the book he reads, the philosophy of time travel. It reveals that this sequence of events has happened several times before, and always ends with a person somehow causing their own deaths. One example is a man who makes an arrow, and is shot by the same arrow, but there's no shooter. He was the shooter, in the other timeline.
What's just a important is Donnie knows this. Donnie knows that in order to end this, he has to die. One of the reasons he laughs at the end is because he realized the higher power, sending him messages to follow, was setting him up. Not only do his actions lead to multiple people dying, they also show him that the world is genuinely better off without him. Everyone is happier.
His sister and mom won't be in the plane that explodes because they'll be grieving for him, and his sister won't be able to compete. Since his sister won't compete, the Asian girl will win the talent contest. The flood and arson won't happen, so the teacher won't lose her job. The self help guru will understand how wrong and terrible his addiction is, and hopefully get help and change. The psychiatrist will realize that not all people who have visions are crazy. Two innocent people will live.
And that's it, really. The higher power...well... they made him do it.