Just a thought…
Lost has always been a show that has centred on conflict from two opposing sides. The early reference to backgamon showing how 2 opponents operate when in battle. Its happened throughout the shows history. The survivors vs. The Others. Jack as a man of science vs. Locke as a man of faith. Ben vs. Widmore. and it would appear to be rooted in the oldest of conflicts, Jacob vs his unnamed rival.
Now all we the viewer know about their conflict comes from the opening of The Incident. Jacob appears to ‘bring’ people, human beings, to the island, an action which angers his rival. His rival seems to have a great deal of cynicism about outsiders. They come they fight they corrupt. Jacob intends to prove him wrong. He obviously must see the good in mankind.
what is most intersting is when Jacob says ‘it ends only once, everything else is just progress’. To this his rival turns hostile. what ends only once? I personally think its the cycle, a cycle that will eventually result in one of their deaths. one triumphing over the other.
I think these 2 individuals are dependent on one another. whatever happens in the loop therefore breaks this dependency and one is able to kill the other.
I personally am trying to formulate a theory that both these men are in fact the same person, just of different age and somehow caught in the same period of time. Further to this, i believe they could both be Aaron, one a version of him raised by Claire, the other a version raised by someone else. Two conflicting versions of oneself.
Obviously i have no evidence of this! but i will keep digging and formulating.