I believe that the island is a "touchstone" or portal where parallel worlds can be accessed. The "hostiles" or at least some of them such as Richard and Jacob are native to the island and are not subject to regular time. I think that Jacob is possibly one of these, but was "captured" by Ben and is being held captive in the shack. Perhaps Richard is the "Esau" to Jacob and is trying to take back his birthright, the control of the island. In the biblical story of Jacob, Jacob wrestles with "an angel" who as daylight approaches, begs Jacob to let him go. Jacob agrees, but asks for a blessing, the angel touches him on the hip socket giving him a permanent limp. Jacob also had a dream where he saw beings of light ascending and descending from "heaven". In the shack, Ben doesn't want Locke to bring the flashlight in.

In the scene where Juliette is wanting to leave the island, Ben persuades her to stay, saying that her sister will be cured from cancer if she agrees to stay. He then takes her to a station where she can see her sister and her sister's son playing on a swing set. Ben asks Richard to show the newspaper, which has the current date printed on it. I suggest that her sister from her world, died. Richard traveled to a parallel world where her sister never contacted cancer and filmed her with her child.

I also think this explains why children cannot be both concieved and born on the island. Danielle was pregnant before she arrived, she had Alex. Claire was pregnant before she arrived and could bear her child. Sun has concieved on the island and like the other women who concieved on the island, she won't be able to have a live child. Something to do with the "outsideness" of the portal. The child wouldn't belong to the other parallel worlds, what happens on the island is off the grid.

In the "Forward Flash" from the season finale, It would seem that Jack and at least Kate and some others were "returned" but to what world? In the hospital, Jack says to the doctor, "Go upstairs and see my father, if I'm more drunk than he is you can fire me." In this world his father didn't die in Australia. In this world they could all return, because this was the world where the oceanic flight crashed into the ocean and was found in a trench with all the dead bodies on it. There would be no "doubles". Jack is depressed and unhappy because it isn't the right life. It all feels wrong -- he wants to fly everywhere on the "Gold pass" or whatever it was called, in the hopes that the plane will crash and he can find his way back to his world via the island. He tells Kate that he doesn't care about any of the people on the plane -- he doesn't care because they're from another "world". In his apartment there are maps lying about all over the place. All sorts of minute changes are present in the parallel world. Sort of like the parallel worlds in the Golden Compass series by Phillip Pullman.

This would explain the four toed statue. Evolution made some minute changes in some other parallel world. Perhaps that's why they let Michael and Walt go. Remember the question the Ms. Klugh asks Michael about whether or not Walt was his biological child? She also questioned him on whether or not Walt ever "appeared" somewhere where he wasn't supposed to be. I think that Walt is someone from the survivors world who is evolving into being able to transverse the universes without using the island as a portal. He was just learning and trying it out when he appeared to Shannon, wet and whispering backwards. He got it right last night when he appeared to Locke to prevent him from killing himself.

Just a few thoughts. I have so many, so I'll save some for another time. Let me know what you think!