INTERLOPERS

The cable TV ads have been hyping a new sci-fi series, The Intruders, in which the premise seems to be that undead spirits come back to take over bodies of real people in order to do no good.

Why spirits would need to take over human bodies to do their evil deeds is unknown. The classic ghost story has transparent forms causing havoc in people's minds. It is like when the smoke monster, MIB, took the form of dead John Locke. He really did not have to so it.  At the time, some speculated that it needed to have a dead body in order to reincarnate in its form. However, MIB/Smokey did it without a body with island Christian.

The premise could be an explanation of the two different worlds LOST created in Season 6.

In the sideways world, all the characters were dead. Dead for a long and short time. If this is the true point of beginning, that the characters were dead before the series began and dead before getting on Flight 815, then perspectives change.

If everyone was dead already, and living in a purgatory setting as boring and mundane as their past lives on Earth (which they have repressed including their own fates), how do dead souls dream?

One would expect that being spirits, their dreams may not be confined to a human brain in REM sleep but could be projected without physical limitations because spirits are closer to energy beings than humanoids.

Perhaps this collective spiritual dream state created the island story. (This is the exact opposite position that most viewers perceive the series based on how events unfolded over the years).

The island could be a fantasy island for the dead.  Think about it: the main characters did irrational, stupid, crazy things without thinking about the consequences. It was an adventure vacation for some. It was an intense emotional soul search for others.

Now could the spirits rematerialize as human beings in the real world? Perhaps.
Or would it have been easier to commandeer human beings and steal those bodies for their vacation fun?

The physical imagines of the characters are the same in the sideways and real world, but that is a matter of convenience. Sideways Jack spirit was someone else's ghost who just wound up in real world Jack's body. And the interloper theory helps explain why some characters had dramatic life shifts after boarding Flight 815. This would include the experienced pilots, who lost control of their plane. It also includes Jack, whose human body and mind would not have become the "leader" that spirit Jack wanted to be in the sideways world.

The main characters were kidnapped by sideways world spirits who needed to re-live some part of their lives in order to break the bonds of their purgatory.