THE LOCKE NESS MONSTER

You are what you are.

And . . . you can't tell me what to do!

The lasting frontal lobe demons that lurked inside the skull of John Locke.

Of all the passengers on Flight 815, Locke was the most angry and bitter. His final dream, an outback adventure, was ruined by his paralysis. He knew then he would be nothing but a cripple. He felt helpless, alone and betrayed by his father, his mother and the world.

In the after math of the plane crash, we first see Locke on his back, struggling to get up. There is a weird expression on his face (and a new non-bleeding scar on his face) as he begins to move his legs.
For no apparent medical reason, the plane crash "caused" or "healed" Locke's permanent paralysis.

Which leads to two plot points of polar opposite conclusions.

First, if Locke was "alive" and survived the plane crash, the miracle had to be chalked up to a) the island's alleged healing properties or b) magic.

Second, if Locke did not survive the crash, his body may have been "taken over" by a smoke monster (which we saw later on in the series by MIB).

The evidence gets option one is compelling since a) pregnant women died on the island; b) people died of gunshot wounds (lesser trauma) than the plane crash; and c) Locke was shot by Ben in purge pit and should have died there.

If Locke's character was a smoke monster from the very beginning of the show, it would cast the series in a different light. Locke's theme was a man of faith. He was reckless, not very smart, impulsive and emotional. The exact opposite traits of Jack who was cool, collected, smart, with medical skills and detached emotions.

Like Locke, Jack's was found after the crash lying on his back. He was shocked or surprised that he had survived. So, like Locke, there are two ways to interpret Jack's awareness of the island: as a plane crash survivor or as another smoke monster.  The latter would balance out the black and white; faith verus science themes of the show.

And like a childhood game of make believe, if two island smoke monsters inhabit the bodies of two dead humans (and use their memories and skills to play a clever game of island senet), then LOST becomes a very complex and deep science fiction epic.