The two basic forces or movements in Lost are Freedom vs. Entrapment. These two could also be expressed as Free Will vs. Determinism (Fate,Destiny) , Faith vs. Science, Light vs Dark, God vs. The Devil etc.
The Island is a site within the world where deterministic order starts to break up into realms of greater and greater freedom. ("A place where miracles happen"). A person enters those realms by surrendering their wish to control things (to fix things), surrendering their attachments/fears. As one surrenders to the island they are able to channel "magical" powers. There is a hierachy on the island of those who have penetrated into the mystery. However, one person may have surrended so far, gained powers and then held onto those powers to control and obstruct those coming behind them on the island.
The best image to encapsulate the basic battle is the scene at the end of Return of the Jedi when Luke throws down his lightsabre and refuses to fight (surrendering to the force, not just channeling it). As it turns out Vader is then moved to help. (Like Ben Kenobi's surrender, the end is becoming one with the force).
I'm guessing that the climax of Lost will have a similar great leap of faith by Jack against an impossible foe or situation. At this stage it seems to me like the M.I.B. wants to get off the island to enslave the world and is the biggest personification of the entraping force. Although it could be any character or thing that has the same effect (Widmore, Eloise Hawking, The 'Cursed' Numbers, A Bad Father etc.)
Comments welcomed