MiB's identity, the loophole, the sickness. by cheeto999

So I think we had some major hints during "Across the sea" as to who the identity of the man in black is, not only during this episode but the whole season.

He's someone we already know. Someone whom he has taken the form of. I think he's always been John Locke, not that he has taken his form, but rather than looking at Jacob and MiB as two sides, light and dark, we must look at the individual. This duality exists within every person. I believe Dogen said as much earlier this season. What if the log ride to the cave separated MiB from himself. His dark side (not in the star wars sense but rather the side that is absent of light) escapes in the form of the black smoke and he goes around the island extinguishing any light he finds because he cannot feel it within himself. He resents it even, as in Eko "doing what he had to do to survive" = tree smack.

However, his light side has endured. It is "reborn" in the form of John Locke, (possible immaculate conception that his mother referred to - although I never liked that line). He knows so much about the island, because he spent another life there, and because a part of him still endures. He is in tune because part of him is the protector of the island.

Evidence: When Richard visited Locke in season 4 he had those objects he had him choose from. He picked the KNIFE not the compass. Not the same knife he used, but a knife nonetheless. Something both MiB and Locke would use as a weapon of choice, (Also note the Smokey picture he drew as a kid).

Desmond: He can see the matrix right now. He looks at John Locke and says, "your John Locke".

Boar hunting. MiB is great at catching and eating Boars, so is John.

Both survived hatch implosions: did anyone not think it was strange how both MiB and John woke up outside of a collapsed man-made station to study electromagnetism. Maybe someone got them both out, but regardless it was still oddly familiar.

John speaks of sacrifices that the island demands. Is this because he was one such sacrifice? Twice even.

Loophole: I believe this is why John is the loophole for the MiB. He has reclaimed his other half. Now that he is complete again he is free to carry out his designs (he was only ever able to materialize fully for an extended period of time once John was dead - or appear on the Beach, we never saw smokey outside of the Jungle until he got John, now he island hops). The problem is that by accessing John's form and his memories, he has not only reclaimed his light side, but his light has reclaimed him. This is why we see traces of John in him, this was part of who he always was. If he and John were always the same person, then once they are combined he would have assumed his whole form, which is why he can't appear as other people anymore.
Evidence: Again that scene in season 4. He is playing backgammon, and Richard remarks that he seems like he knows "the rules"

Sickness: The sickness is simply the light in you being put out. It can be reignited through other people. But once the "darkness" takes you like it did Said, you become like the MiB *was* before he took John.

I believe this theory works because it seems like the strangely/frustratingly obvious thing the writers would do. Because then you go back and watch the entire show differently. As to how this would relate to the alternate timeline, perhaps the bleed-through effect from light John to Dark John would cause the light side to take a more active role in the Dark John form, and vice versa. The latter would be extremely interesting to see.