The Big Unanswered Questions Of Lost Part One.

1. What was the nature and purpose of the Island?

Although it is never said outright I don't believe the island itself has any purpose, it is simply an Island. When Locke believed that the Island had some purpose for him it was simply the smoke monster manipulating him to kill Jacob. The same can be said of Jack seeing his dead father. The Island is special in that it seems to be the source of "the light" (I'll talk more about that later). The laws of time and space also seem to converge on the Island allowing time travel and alternate universes to exist. The Island though doesn't truly have any will of it's own as we find out that most events were manipulated by Jacob or "The Man In Black". And as we find out in the final episode the way Jacob protected the Island was entirely up to him.

2. What is "the light"?

Jacob's mother describes it as "life, death and rebirth", so we can assume it involves the cycle of life on earth or throughout the universe. I believe this was left very vague because we're getting into philosophical and religious ideas with this one. The writers obviously don't want to tell anyone what to believe in this regard so they left it rather murky. However, with the term "life, death and rebirth" I think they are hinting at the idea that all life is from past life. That all energy is from past energy and cannot be added to or taken away. Again this is just a philosophical idea. The light is somehow keeping this balance from crumbling. As we saw in "The End" when Jack releases the light the Island begins to crumble in on itself. I believe had it disappeared completely then everything would have ceased to exist.

3. What would have happened had "The Man In Black" escaped the Island?

The truth is we really have no idea. According to Jacob this would be the mean the end of everything but "The Man In Black" said he simply wanted to leave to have his old life back. So it depends on who you believe. However, we can assume from his actions on the Island as the smoke monster that he does not have a high regard for humanity.

4. Why did "The Man In Black" transform into the smoke monster?

If the light is a source of good in the universe then why would it turn "The Man In Black" into a monster? Why were other characters not also transformed? I don't really have a good answer on this one so I'll leave it to someone else.