Interesting theory that i just read, and one that i can't seem to fault:
Three Black Swans...
In the Key to the Whole Game, I suggested that the Island is a place where the laws of quantum mechanics apply at a macroscopic scale. Like Doc Jensen at EW.com, I believe this makes the Island a source of miraculous Black Swan events that change what's "supposed" to happen against all odds. So far, we've witnessed two such miracles, and I'm guessing we'll see a third before the show is done. These three Black Swans are integral to Jacob's plan to save us all.
The Valenzetti Equation. Before going further, let me clarify one important piece of mythology you may not have picked up from the show -- the Valenzetti Equation. Here's all you need to know courtesy of Team Darlton themselves from a 2009 interview with E-Online:
The Hanso Foundation that started the Dharma Initiative hired this guy Valenzetti to basically work on this equation to determine what was the probability of the world ending in the wake of the Cuban Missile Crisis. Valenzetti basically deduced that it was 100 percent within the next 27 years, so the Hanso Foundation started the Dharma Initiative in an effort to try to change the variables in the equation so that mankind wouldn't wipe it itself out.
The Valenzetti is a mathematical expression of our destiny as a species. When someone saves the world on Lost, they do so against the dictates of fate. The universe then course corrects, resetting the doomsday clock. That's what the Man in Black and Jacob debate with the Black Rock off in the distance. Since ancient times, Jacob has brought people to the Island to create Black Swan events that postpone our extinction -- an exercise the Man in Black finds futile. None of what we've seen was supposed to happen, but all of it must or "God help us all."
Black Swan 1: The Incident. The first miracle is the one just depicted in the Season 5 finale. DHARMA was supposed to cause an extinction-level event by drilling at the Swan site, but our Losties changed that by causing the Incident instead. Daniel was right that Ms. Hawking lied about this being their destiny. They're "variables" precisely because the Incident wasn't supposed to happen, so "whatever happened, happened" doesn't apply. Eloise's lie was a noble one meant to preserve the fragile time loop in which our Losties save the world.
That's also why Jacob touches several key players in the Incident at pivotal moments in their lives. Because this isn't their destiny, he can't simply depend on course correction to get them where they need to be. Maybe the best example is when Jacob gives the pen to little James. If the latter doesn't finish that letter, chase the real Sawyer to Australia, crash on the Island, travel back in time, and pull a Han Solo, the assault by Jack and Co. on the Swan site most likely fails. The world ends right there in 1977.
Black Swan 2: The Fail-Safe. The second event is also one we've already seen. The Incident merely reset the countdown to catastrophe. The Swan button protocol was supposed to finish the job, but Desmond saved the world in defiance of the Valenzetti by activating the Fail-Safe. The catch is that, like the Incident, none of this was supposed to happen. When Desmond traveled back in time, he too was a variable who could have changed things despite the rule of "whatever happened, happened." Don't you dare rewrite history, Desmond!
That's why Ms. Hawking intervenes to prevent Desmond from proposing to Penny. As with our Losties, Eloise lies when she implies it's his destiny to go to the Island. Here again, however, her lie is a noble one meant to preserve the miraculous timeline in which the world is saved. If Des doesn't choose to go to the Island, press the button, and turn the key, then as Ms. Hawking says, every single one of us is dead. The Swan implosion sucks up everything on Earth, ending the world in 2004. As Jon G notes, that's exactly 27 years after the Incident.
Here's the really hellish part. Ms. Hawking realizes that Black Swans 1 and 2 are inextricably linked by the time loop we've witnessed -- it's all one big predestination paradox. Our Losties can't cause the Incident in 1977 unless Desmond turns the key in 2004, and vice versa. Eloise, moreover, only knows about these events because of Daniel's notebook. That's why she sends Daniel to the Island despite knowing he will die at her own hands. Ms. Hawking sacrifices her only son to complete the causal loop that saves the world.
The Man in Black's Loophole. The Man in Black knows this loop is necessary and cynically exploits it to his advantage. He uses the Smoke Monster to make a copy of Christian's body, then tricks Claire into helping him enter the Cabin. This allows the Man in Black to claim to speak for Jacob when Locke arrives looking for help. The Man in Black instructs Locke to move the Island, but omits crucial information on how to do so. When Ben turns the Wheel off its axis, the Man in Black uses the resulting time skips to get Locke off the Island and plant the notion that he must die.
All of this is the Man in Black's plan to to create the Loophole that enables him to kill Jacob. I think the rules of their game are simple. Neither player can kill the other -- the Man in Black must persuade someone else to do the deed. Jacob's death, moreover, must take place inside the Foot, where only his Chosen Ones can enter -- notice how even Richard stops at the door. That's why the Man in Black goes to such elaborate lengths to obtain Locke's corpse. The Man in Black needs to copy the body so he can enter Foot as Locke and incite Ben to murder.
It's so diabolical when you think about it. The Man in Black knows that, even if Jacob and Eloise discover his plot, they can't stop him for fear of disrupting the delicate chain of events leading to the Incident and Fail-Safe. So confident is the Man in Black that, as Zombie Christian, he actually directs Locke to find Eloise knowing she has to send Locke's body back to the Island with the Oceanic 6 to ensure they end up in the past. What the Man in Black fails to realize is that Jacob has been running his own long con to create Black Swan number three.
Black Swan 3: The Omega Point. The third miracle is one we're about to see. If I'm right about the Valenzetti, the Fail-Safe simply delayed our extinction until no later than 2031. Jacob hopes to end this vicious cycle for good by creating the Omega Point. The term was coined by Pierre Teilhard de Chardin to describe a global collective consciousness that he believed we're evolving towards as a species. The concept is quite simiar to the new-age Gnostic notion of the Supermind that I described in 108: Restoring the Lost Sun.
The clue to Jacob's objective is the book he reads while Locke falls in the background. Everything That Rises Must Converge is a collection of short stories by Flannery O'Connor, who took the title from Teilhard's description of the Omega Point. Ironically, O'Connor's stories feature characters who exhibit the sort of bias and prejudice that the Omega Point aspires to overcome. The book works well as a metaphor for Jacob's plan to permanently cure what the Man in Black described as humanity's tendancy to fight, destroy, and corrupt.
Before that can happen, however, both Jacob and the Man in Black must die. The Island is a Vast Active Living Intelligence System that regulates our biosphere -- basically, the brain of the world. Like the human brain, it has right and left sides that should work together as a unified whole. Unfortunately, some ancient trauma gave the Island what amounts to Dissociative Identity Disorder, creating two opposing personalities, light and dark. Jacob and the Man in Black aren't supposed to be perpetual adversaries. Their division prevents our evolution as a species.
The only solution is to wipe the planetary brain clean and start from tabula rasa. The Man in Black believes the murderous Loophole is all his idea. But Jacob sees it coming a mile away and uses the Loophole to make both of their deaths a fait accompli. He manipulates the Man in Black into assuming Locke's physical form, which leaves the latter vulnerable to being killed. As Locke, moreover, the Man in Black has publicly declared his desire to kill the Others' beloved leader. No wonder he doesn't seem particularly triumphant upon kicking Jacob's body into the fire.
When Jacob and the Man in Black are dead, two new avatars must take their place. To heal the Island's division, however, they must transcend the opposition of light and dark. For this reason, I believe Jacob and the Man in Black's replacements will be a man and woman in love. My inspiration here is Aristophanes's account of love in Plato's Symposium. Once, according to Aristophanes, human beings were round creatures with two heads. Fearing our strength, the gods split human bodies in two. Love is the desire to make yourself whole again by finding your other half. Kind of like the Yin-Yang.
I'm guessing, moreover, that the happy couple will be two children of the Island we've already met. One half is Aaron, who was conceived off the Island but born on it. The other is Ji-Yeon, who was conceived on the Island but born off it. Remember what Sun tells little Ji-Yeon on the phone? "I met a new friend for you in America. His name is Aaron." I believe that East will eventually meet West and fall in love. Everything that rises must converge on a Lost wedding between Aaron and Ji-Yeon before 2031. Our survival as a species depends on it...