The MIB assumes that men are corruptible by their very nature and Jacob wants to prove him wrong. Why?
We know that the next episode is going to give us more details about MIB and Jacob's origin. The promo flashes good vs. evil and dark vs. light. What does that really mean? Through out this season both characters have shown some redeeming qualities and some have shown some not so redeeming qualities. If you follow the Biblical story of Jacob and his brother Easu you will find many parallels. One that I found most interesting is that Jacob spent the later part of his life in Egypt. That could explain all of the Egyptian temple, the statue, and so on. Here are a few hypothesis that I have made.
Fate and Destiny
Jacob went to live in Egypt and became familiar with their belief system. The island is the gate way to Hell. It is not actually Hell. It is sort of like purgatory. It is a place of redemption and a place for eternal judgment. I think that is why some of the ghosts can't leave. (Just speculation but I suspect that there will be a surprising twist at the end)
Theories about the end game
Rose and Bernard are at peace because they are content with one another. I think that will play a pivotal role at the end.
The Dharma initiative Ellie, and Widmore will all come together and explain many of the island's mysteries. One is that the island is some how connected/related to places like the Bermuda triangle. The history of the island is created to the other unsolved mysteries of the world. For example the lost city of Atlantis, vortexes like the one in Oregon, the disappearance of the people on Easter Island, or even Stone Henge. (This is all just speculation, but it is fun to consider)
Good vs. Evil. I think that Jacob and the MIB are both. If the MIB escaped the island would the world come to an apocalyptic end? First of all I have a problem with the biblical story of the apocalypse because historically it has influenced/justified Western dominance and ethnic supremacy. Anyone remember "Manifest Destiny"? Even if our time traveling island dwellers have witnessed their tale/story playing its self out why are they still caught up in their own little battle? Could it be possible that the Christian God/Gods are as flamboyant, self centered, and child like as the Greek Gods were? How ever the story plays out it will make a statement about how we perceive values. It will be a statement I highly doubt that the Judeo-Christian version will be as triumphant as some might think. Values like cats are highly unpredictable and you can't change/train them. But wait! What happens when our values become subject to change. What if our beliefs are all up to chance ! and circumstance. What if we have no control over anything? We might follow the slippery slope for a while, but then we would be forced to come back to reality. This game that we have been playing all along has surrendered to chance. There will not be a triumphant victory, and there will be no check mate. Perhaps the end game will be a tie.
I also think that there will be some type of redeeming ending for the MIB. Sort of like Darth Vader. I think that Jacob and the MIB will make amends in this life or the next. This redemption will not come without a hefty cost.