I though this was a decent theory,
"1. The show is about the characters but the MYTHOLOGY OF LOST is about good vs. evil and the clues have been there since day one people. The clue in the Pilot (1.02) is Locke explaining Backgammon to Walt. He says "one side light, one side dark" and says the "game" is 5,000 years old. In House of the Rising Sun (1.06) they find a bag with one WHITE and one BLACK stone in the cave with Adam & Eve. In Raised By Another (1.10) Claire has a nightmare where Locke has one WHITE eye and one BLACK eye. In The Incident (5.16/5.17) Jacob wears white (good) and The Man In Black wears dark clothes (evil). He wears black both when he speaks to Jacob in the beginning of the finale and when he appears as Fake Locke at the end when Ben stabs Jacob.
2. The Man in Black (Shout out to The Dark Tower) appears as many forms of evil throughout the series of Lost. He appears as Smokey and many DEAD characters on the island such as Christian, Yemi, Horace, Alex and finally Fake Locke.
3. The Man in Black pulls The Long Con on everyone with his loophole, which I will do my best to explain. The fued between Linus and Widmore is important and The Man In Black has been influencing events forever... but the CRITICAL part of his plan starts with Locke. Somehow Jacob TRAPPED The Man In Black in the cabin. He somehow escaped. As explained in The Incident - Bram points out the ash circle has been broken. Ilana says, "he (Jacob) hasn't been here for a long time. Someone else (Man In Black) has been using it. Burn it." In Man Behind The Curtain (3.20) it was The Man In Black that said "help me" to Locke, NOT Jacob. In Cabin Fever (4.11) The Man In Black appeared as Christian and LIED to Locke, saying he could speak on behalf of Jacob. He starts the most important part of his plan to kill Jacob when, as Christian, he tells Locke to move the island... so that Locke will leave the island and can be killed. But Locke, being the gullable idiot he is, allows Ben to turn the wheel. So The Man In Black needs to fix this mistake. He appears as Christian again in the bottom of the well and tells Locke, "I said YOU have to move the island John." This time Locke does and leaves the island where he is killed. When Ajira 316 returns, Locke is NEVER reincarnated. Dead is Dead. The Man In Black now appears as Locke and manipulates Alpert and Ben masterfully all the way to the scene where Ben makes a selfish choice and stabs Jacob.
4. Jacob visiting the Losties. He "touches" ALL those who he visits. Literally touches them and in some way marks them to be someday DRAWN to the island. The only person who did NOT have Jacob in their flashback in the finale? Juliet. Because Jacob never BROUGHT Juliet to the island. Linus did. And Juliet just died. Coincidence? I think not.
5. A Candidate. This is just a theory but when Bram mentions that Lapidus could be a "candidate" to Ilana... I believe this is the "proof" Jacob needs to "win" the game and PROVE The Man In Black wrong. The Man in Black said to Jacob "You still trying to prove me wrong? Jacob replied: "You ARE Wrong." This is the HEART of the fundamental debate between Jacob and The Man in Black. "They come, they fight, they destroy, they corrupt. It always ends the same" says The Man in Black. "It only ends once" says Jacob. "Anything that happens before that... is just progress." Jacob needs a pure soul to prove The Man In Black wrong. A candidate who is morally pure and unselfish to do the right thing. A person to prove humanity is capable of good and not just fighting, destruction and corruption. This, I believe, is what Jacob NEEDS to win and why he has been summoning people to the island for ages. From the Black Rock to Oceanic 815 to Ajira 316 and everyone in between. To find that ONE soul to prove to The Man In Black that he is wrong. Bram is wrong though... it's not Lapidus... it's Hurley.
6. Whatever happened, happened ("WHH"). I've argued this one enough. Bottom line is, NOTHING CHANGED bt the Losties being in 1977 Dharmaville because they were ALWAYS there. Time is linear, but Lost is shown through the perspective of the chatacters. Despite showing season 5 through the vehicle of time travel and Darlton confusing everyone, The Losties ALWAYS were in 1977 and it only happened once. The Incident was always caused by nuke as Miles said. Chang still lost his arm, Radzinsky still lived through it and will eventually shoot himself in The Swan, Faraday still told Charlotte to leave and never come back, Charlotte still said "I'm not allowed to have chocolate before dinner" and she still left on the sub as did baby Miles and Lara Chang. Linus still lost his innocence and became an Other. The Losties will NOT land at LAX in season 6. They will NOT wake up on 9.22.04 with new memories and start again. Season 5 was their present. The last thing Jacob said before the Man In Black kicked him into the fire was "they're coming" and The Man In Black looked terrified. The Losties are coming. Season 6 will start with their arrival in the present time where Alpert, Sun, Ilana, Bram and everyone else is outside the statue."