What they died for by Aaron from Madison WI

I have not fully "fact" checked this theory, but it seems to be working for me right now. I realize alot of this is obvious or posted already in other theories. But this is more for my own clarity, and to hear you all everybody's comments, thanks.

How bout this, lets work backwards (or forwards ;) )
The most important thing in the universe was that the light source never left the island, if it did, the world would basically cease to exist. Mother and mother-before-her kept this secret safe for eternity until Jacob and MIB were brought to the island. When the smoke monster was created, part of the light sources' energy was transferred to smokey, therefore if smokey left the island, the light sources' energy would get free and the world would end.

Jacob's job now became more difficult: not only would he need to protect the source, but he would have to keep smokey from ever leaving the island. He took steps by hiring Richard to help him bring people to the island and protect the source/stop smokey. Knowing that his brother was hunting for access points to the light source, Jacob and co. built a temple surrounding one of the access points (the pool where Dogen and Sayid died). Jacob protected this temple from smokey. People who were on board with Jacob were brought to the temple as a refuge from smokey, knowing they would be safe under Jacob's protection. As long as their leader was alive.

Over time Jacob realized that he could not do this forever and much like his mother he decided to search for a replacement for himself. He created the mirror system which would monitor specific people who fit to his model of a replacement for himself, and he numbered them. The MIB secretly knew of this list and copied it onto the walls of the cave he lived in. Jacob called these people his candidates, and gave them his protection from the MIB. However, MIB discovered that although he couldnt kill them directly, he could trick them into killing each other.

In addition, Jacob left the island and appeared to many candidates over the years, or he would send Richard (or perhaps Eloise or Whidmore/Abaddon or possibily Dharma/Hanso members) to do it for him. He would gently push these people to the island increasing his chances of finding the right person. Hundreds of years passed, with Jacob bringing people to the island, some of which lived at the temple, some tricked by smokey into killing each other, but none of them were Jacob's true replacement. Because now Jacob couldnt just appoint a replacement to guard the light, he had to find the one who could destroy the MIB (because Jacob was not allowed to hurt his own brother). He doesnt have this oppurtunity until Whidmore/ Eloise/Farraday discover Desmond's specialness.

That is until this final group of survivors from flight 815 crashed. Jacob realized that amongst this group was the true candidate, the one who could not only replace him but defeat smokey. But Smokey knew this too. However neither knew which one it was, although the list was getting shorter and shorter.

Everything we saw from Seasons 1-5 were essential to the story in the sense that they led to the realization of Jack as the True Candidate (the True Candidate being the only one who could replace Jacob AND kill smokey). However Jack could not do this alone, Jacob knew that he needed Desmond to undo the mistake Jacob made when he created the smoke monster in the first place, and immortilized his own brother.

Therefore Everything that Happened in those seasons Happened. And the entire story was the most important events that had ever happened, or ever would happen to any of these characters in their lives. Because Every event led to these things:

1) The remaining candidates coming to the island
2) Desmond pushing the button and realizing his specialness
3) Jacob appointing Jack as his replacement
3) Jack ultimately killing the MIB/smokey
4) Jack appointing Hurley as his sucsessor
5) Hurley protecting the now intact light source

And that is why we see all of them together in this afterlife, they were all essential to the worlds' survival. This is "what they died for" and so they were all given a chance to collectively create a temporary world where they could grasp redemption of their own lives and/or a second chance at love before moving on to death.

Thanks, cant wait to hear your comments everybody! Namaste