Island Hub by Dark Phil

I have been re-watching S5, and I recommend it to everyone. This theory supposes that there are a near infinite number of timelines.

Any place in your life where you make a decision essentially creates a new timeline. The Island is a "hub" where you can connect to any timeline.

Any flashes we have seen (backwards, forwards, sideways, oceanic, etc.) represent a different timeline. When we see the Losties in these flashes we are seeing the Island Lostie, but they are in an alt timeline.

In S5 Ep 2, The Lie, Sayid wakes up from a tranq dart at the hospital and starts choking Jack. He was coming out of a different timeline where he was fighting for his life. Also in this episode, Jack and Ben are at a motel room. Ben packs up to leave and Jack says, "Where are we going?", and Ben tells Jack to go home, get a suitcase, and pack up anything in this life that you love, because we won't be coming back. Ben knows this is an alt timeline, and even if they get off the island, Jack won't be returning to this timeline.
Ben is conning us in S6. I do not believe he is as clueless as he has been playing. He knows how to call Smokey, he knows about the frozen donkey wheel, and I believe the above example proves he knows about the alt timelines. He was also the one making sure John Locke's body returned to the island.

The Oceanic 6 exists in an alt timeline. There is a timeline where the plane crashed and almost everyone died, except for the O6 and the other people they said died after the crash. However, our Island Losties entered the consciousness of the real
O6, and told a lie they didn't need to tell. In the real O6 timeline there was no Island, no smoke monster, no one left behind.

There was a timeline were the plane crashed to the bottom of the ocean and everyone died, unless you believe Widmore about planting the plane. However, he may have said that to cover up the alt timeline. If Ben knows about the alt timelines, then Widmore does too.

When Jacob brings people to the Island to prove they are good, or incorruptible, they are playing the game in their alt timelines. Their past doesn't matter. As in the past of their alts. They are inserted in the alt timeline to make a good, or noble decision. MIB manifests himself in the alt timelines to try and corrupt them, like Locke in the substitute.