What Happens When a Character Dies by Scott Gingold

This is a rather simple theory aimed at ironing out all the different ways in which we've seen the afterlife on Lost. I tried to give an order to the stages of death using evidence shown on the show.

Remember, that since time is relative (and since Christian said that time doesn't exist in the Sideways universe) all of this stuff can still happen in order, but in the blink of an eye (literally).

1) The character dies in real life.

2) The character's last thoughts can be heard by Miles or the Man in Black if a body/ashes are present.

3) The character's ghost can speak to Hurley or any other living person it chooses to speak to. They also whisper. These ghosts are those who have not yet moved onto the Sideways Universe. They are not necessarily trapped on the island, since we've seen other ghosts and whisperers who have appeared off the island: Libby in Michael's hospital room, Libby on the freighter, Ana Lucia as a cop in LA, Eko & Charlie at Santa Rosa, etc. This ghosts have the ability to help the living. These ghosts have full recollection of their past life and they know they are dead.

4) Once the ghosts help who they have to help, or make peace with who they have to make peace with, they can proceed to the Sideways Universe. In "The New Man in Charge", we're led to believe that if Walt returns to the island to make peace with the ghost of Michael, Michael will be able to move on.

5) After that happens, the character will then wake up in the Sideways Universe with no memory of their past life. They use the time in the Sideways Universe to remember their life and to let go of their bad feelings about themselves. Some of the characters in the Sideways Universe (Ben, Eloise) choose to stay there so they can continue to work out their issues and help others. Some of the characters die in the Sideways Universe (Mikhail, Keamy) which I took to meant they return to Earth as a ghost until they make peace with or help the living again and then are given a second chance at the Sideways Universe. The Sideways is like a cleansing process to prepare the souls to move onto the next step. Once they've remembered and are ready to move on, they step through the church (or another portal that is significant to them) into the bright white light.

6) I believe that once they step into the light, they become absorbed into the source that exists in the center of the island and in the heart of each individual on Earth. The light is every person, but it's also inside the island and in specific pockets throughout the world. It's able to heal the sick and bend time and essentially think for itself because it's comprised of all the souls who have moved on. This is why the lighthouse was able to show Jacob where Jack used to live. Because it was controlled by the light of the island which in it had the soul of Christian Shepherd. This can be said of every character on the show who had some connection to someone who had died whose souls are now entwined with the island, allowing the island to pull them there. The island is a living breathing entity because it's composed of all the souls of the dead.