Some things to take note of by Sebastian

Having just watched the finale, I am--for the most part--completely content with how things ended. A few quick things to note:

Yes, it was purgatory the entire time, not simply an "alternate universe." When people die on the island and are unable to move on, they become whispers, explaining why Michael was not with them when they moved on. Christian Shepard said that "now" was all relative, so it isn't that all these characters simply died, but that when they do EVENTUALLY die they all experience a cathartic ending with the people who impacted their lives the most. Jack is dead, so his purgatory comes to fruition, whereas survivors like Sawyer and Kate may live full lives but experience the same outcome when they do eventually die. This is best explained in the way Hurley says to Ben: "You made a great number 2."

Also keep in mind the very first episode of season 6 when Jack calls his mother to ask when his appendix was taken out. That's where "Fake Locke" stabbed him. The occasional blood appearing on Jack's neck is another indication.

Many are confused as to why Desmond and Jack were able to venture into the light without becoming "smoke". Personally, I believe they were able to go into the light because they were chosen to. Desmond had experienced his share of electromagnetism, which I think is simply a "scientific" way of saying that he was used to the light. Jack was able to go in because he was the new "Jacob." I think if anyone, and I mean ANYONE else had gone into that cavern, things would have played out differently. Remember, this is destiny. While free will exists on the island, it's up to the individual person to decide whether or not they want to follow their destiny.

So why did MIB turn into smoke? He wasn't pure of heart, he wasn't "ready," he wasn't meant to go in. Keep in mind that at the end of the day Jacob and MIB are simply human, simply people. They are not Gods, they do not have some ultimate superior knowledge about the way the universe works. They know only that the island needs protecting.

It's important to note, I think, that the island itself is a character. Jacob mentions that he "chose" his candidates because they all had tumultuous lives. While in many respects Jacob intervened in their lives to bring them to the island, it was the island itself which chose the candidates. It's not simply that the island is magical, but that it is a character within itself, understanding that certain people must come to the island to protect it. I don't believe Jacob built that lighthouse, I believe it was there long before him and had already chosen its candidates. Jacob's job was simply to bring them together, whether he thought it was his own choosing or not.

Think about the numbers. While many may argue that they weren't adequately explained, I beg to differ. As we all know, the numbers correspond to potential candidates. The island knew of these candidates long before they ever arrived. In season 1 Hurley meets an individual at a psyche ward who can only repeat the numbers over and over again. When Hurley travels to Australia to speak to someone who had gone to the island, the man explains that he heard the numbers repeating over and over again over a transmission. Any circumstance in which the numbers appeared were simply a way to solidify that these numbers--these specific candidates--were all part of a destiny to lead the individuals to the island.

The island directly influenced everyone on it. Kate seeing the horse that helped her escape was the island's manifestation. Locke seeing Walt right before he was about to kill himself after Ben shoots him in the pit, I believe, is also a manifestation the island created.

This brings me to Christian Shepard.

While MIB declares that he was posing as Jack's father all along, in most cases Christian Shepard was actually himself, a whisper on the island unable to move forward.

When Christian appears to Jack in Season 1 and leads him to the caves, I strongly believe that it was, in fact, NOT MIB. Fake Locke simply told Jack that to gain his trust. He had no reason to lead the island castaways to fresh water if his end-game was to get them all killed. He would have simply let them rot on the beach. I believe in that case it actually was Jack's father brought to "life" by the island.

Remember when Michael attempted to kill himself but it didn't work? That was the island--which IS a character--refusing to let Michael die until he had completed his task, which was to blow up the ship carrying mercenaries, and I believe also an attempt to keep the candidates on the island. When Michael finally completes his duty, Christian Shepard appears and tells him he's done his job. THAT was the real Christian Shepard. After all, MIB would not be able to simply stop Michael from killing himself, and would have zero reason whatsoever to want that ship to blow up, considering he wanted to leave the island. It was Christian's spirit, unable to move on, attempting to guide the candidates to their final destiny.

However, that isn't to say that MIB did not assume the form of Christian at times. Claire's manipulation into becoming a crazed jungle-woman was MIB in Christian's body, just as Yemi confronting Eko was MIB. I believe in some cases MIB did play the role of those who had passed on, but in many cases it was the "restless spirits" of the island attempting to guide our candidates to their ultimate destiny.

So yes, MIB did take the form of Christian, but I think it would be wise not to simply conclude that it was also MIB leading the castaways to water. That actually was Christian, which is why he played such an important role in the finale. He was trying to atone for his past sins, leading Jack to his ultimate destiny.

Another interesting idea, which I'm sure has been discussed before, is the idea that the island itself is a sort of "garden of eden," which explains why when people leave the island they wind up in the middle east, an allusion to where many believe the garden of eden once existed. That isn't to say that Lost is ultimately a "Christian-themed" show. If you pay attention in the finale, you'll see the stained glass windows contain a plethora of religious symbols, not simply a cross.

Yes, there are things that weren't answered. Why was Walt so special? What did the Dharma Initative see in him? Why couldn't Ben and Widmore kill one another (until, of course, they were back on the island)? And, of course, the Hurley Bird.

But whatever. At the end of the day I can look back at Lost and see how truly brilliant it all was, how, for the most part, things came together and fit into place wonderfully. I know these theories are a little convoluted, but hopefully they clear up a few lingering questions.