Some of my thoughts and interpretations of what we have seen in Lost...
The Light
Is timeless unchanging pureness. If a person has more hatred/greed/evil (etc.) in him when he enters it he becomes hatred/greed/evil personified. It takes over their entire being. For such a person it creates a kind of "anti-nirvana" or "hell"
If a person lets go of hate etc. and enters the light the person would reach nirvana, becoming free from suffering etc.
According to Jacob's "Mother", all men are corrupt, greedy, selfish etc. she therefore tells Jacob that it must be protected and that should anyone enter the light it would be "worse than death" - meaning the corrupt, greedy selfish nature would be amplified.
The Bomb
They set the bomb off hoping that it would send them back to before the plane crashed (since no island = no button = no plane crash). This isn't exactly what happened however because it couldn't. If the plane had never crashed then they'd have never set the bomb off. In other words it would have created a paradox. Paradoxes cannot exist.
What happened was that it created a new parralel timeline/universe (the "flash sideways"), one in which everything was very similar but had differences (eg. this time Jack and Juliet met, due to them both being doctors, and married because Ben had never brought Juliet to the island) where the island sunk in the 70's and thus the plane, having never crashed, landed in LAX.
The Parallel timeline
Due to Desmond pressing the failsafe key of the Hatch, and being blasted with the light in a small dosage, he gained some of the properties of the light and became somewhat immune from it. He become unhinged from space and time and could therefore predict future events (Charlies death for instance) and travel, via his mind/soul, in space and time.
He traveled in time within his own reality in season 3 to when he was in the army. However now that the Bomb had created a new parallel reality he could now travel to this. Widmore blasted him with the light again and he did just that. This parralel Universe gave the Losties the chance to do what they wanted to when they blew up the bomb. Reunite off the island and move on with their lives together.
Desmond was the key to them remembering their on island lives and eventual deaths (Libby dieing at the hands of Michael, Jack dieing in the Bamboo patch after saving the island, Kate, Sawyer, Lapidus, Miles, Richard etc. dieing sometime afterwards off the island, Hurley and Ben sometime afterwards on the island). Since they had died some of them were ready to "move on" into Nirvana. Others, like Ben had reasons not to move on just yet - like redeeming himself in the eyes of Alex perhaps?.
Jacob
Entrusted with protecting the Light fooks up straight away. In his rage, at seeing his brother murder his "mother", he sends his brother into the light, creating the smoke monster. Jacob himself is flawed but still holds out hope that humans can overcome their basic instincts. He is proven right when, after many many centuries, Jack, Hurley et el step up to the plate.
The Smoke Monster / Jacob's Brother
Was the result of the hatred in Jacob's brother's heart and character at the time of entering the light. The Smoke Monster became known to past civilisations, such as the Egyptians and Greeks, as Apep and Cerberus respectively and a whole host of other names from other mythologies - "Satan" , "Devil" etc.
The writers never game him a name because he has so many different names, in all these belief systems, already. Good choice imo.
I'm still thinking it all throught to be honest. I like that it has ended in a somewhat ambiguous way, leaving it open to interpretation and discussion. Straight after the finale I was disapointed to not find out some things but the more I think about it the more Im beginning to like it.
Lost is, in my mind, the best show ever created. It was one hell of a ride encompassing everything - morality, science, philosophy, religion, redemption, forgiveness, hate, mystery and the unknown... the list goes on and on. It encapsulated the human condition in all its glory and flaws and did so in such an entertaining way. I'm sad that it's gone but I'm so glad that I was able to see it.
