Perhaps Locke is still alive by jiggaman123

While Locke has indeed been murdered, I believe that Locke now co-exists with the smoke monster/MIB. This is evident in many examples:

-In the most recent episode, flashbacks naturally paralleled reality with the respective characters. This included Locke and though he is dead, his flashbacks exhibit a character much like his former self.

-Specifically there was the theme of limitation. Both of these characters suffer similar challenges.

-Also the MIB seems to behave like an improved John Locke, or at least that's what we're shown (fearless, though still purposeful). Obviously, O' Quinn is the same, yet his characters' visibile similarities seem to imply some purpose.

Perhaps these were just demonstrating serendipity, or maybe the writers were hinting at something. I believe the writers were giving us more than ironies. Is it not possible that when the MIB morphs into human figures ('fore Locke, Christian) he imbibes certain attributes of that person?

Also as an aside, I'd like to give a quick theory on Jacob's figure forming. I believe those characters we've been shown that run or maintain safe distance (ex. little Jacob, Ben's Mom), are the result of Jacob's transformations. In the case of Ben's Mom her body was not on the island. Come to think of it, Dave might have been a test for Hurley. This is either the case or the MIB can transform into those off the island. There may be examples I have missed that prove otherwise.

Thanks for reading, first time post, sorry if I've regurgitated anything, but I sometimes feel that this may be excused by the fact that this website is essentially a hivemind. Peace be to the Internet.