Island never actually existed by Paris77

So it's purgatory- the plane crashed and they all died. There is no actual island. The people that "survived" were people who could not accept their deaths ( from this group Jacob needs to pick a replacement) they needed to accept their death before they could move on- or they needed to complete their lives to be ready to accept their deaths to move on- hence the island didn't actually exist. The "others" were people who had died before and also could not move on. So the island was purgatory.Purgatory is neither good or bad- represented by Jacob and Smokey. Both of them want to move on from purgatory. But they both need to find replacements before they can leave the "island". Hurley and Ben are those replacements. Jack was never meant to replace Jacob- he was the one who had the most difficulty accepting his death-he needed to "fix" the island, be the hero, to finally be able to move on. All that happened on the island, including leaving and coming back, was just a way to have them come to terms with their deaths, and to have the replacements for Jacob and Smokey accept their fate.

There is also something about redemption in purgatory. They can't accept their deaths because their lives are incomplete- the island gives them a chance to play out their lives which in turn lets them accept their deaths. Eg. Juliet had never known love- once she knows Sawyer loves her- she can move on. Eg. Jin and Sun- needed to fall back in love, Jack needed to be a hero, Mr. Echo needed to become a good man, Kate needed to be a mother, Charlie needed to get clean and be a good man, etc, Claire needed to have a real family, etc... Once they do what they need to do and are ready to accept their deaths, they die on "the island" for the sake of those not ready to go. At the end, they all come back to help the final holdouts move on- the biggest hold out being Jack who finally accepts his fate once he "saves" the island.

Now, this would explain the large arc of the Lost six seasons. There are obvious big holes in this purgatory theory, but it would explain a lot of things. It would leave a lot of questions- notably the Dharma Initiave, the time travelling, the big wheel that hides moves the island and transports you to the desert, polar bears, Eloise and Whitmore , Faraday and redhead chick...? The jughead, why people can't deliver babies on the island, why jack needed to operate on Ben, when Ben could have just taken submarine back to the real world, etc...