We are the Wine by Gwmort

I watched the scene with Jacob and Richard on the beach talking about the cork concept. We are led to believe the island is a barrier between hell and earth, but that is never said. All that Jacob said is the island keeps the evil from spreading. He never says "into the world" or something similar.

We know that there already is evil, sin and death in our world. I believe the island is keeping us and our evil from spreading into a perfect world with no evil or sin; paradise.

My theory is that the island is a barrier not between hell and earth, but between earth and heaven. In this model MiB is a guardian of the gates of paradise (perhaps the angel of death) tasked with keeping the evil out. Jacob is trying to convince him that we are good enough now to be let in, but MiB is not buying it. MiB just wants to go back to paradise, but he can't while the island is in danger from Jacob and the evil men he keeps bringing there.

That is why I think MiB isn't killing people who are willing to leave the island voluntarily. He doesn't care how he depopulates the island, just so long as he gets all the people off, and its why he can't leave while Jacob is still around because he would just bring more people. MiB can't go back to heaven until the island population = zero.

I also note that with this theory the island becomes a tangible link between heaven and earth, or in biblical terms "Jacob's ladder".