"The light" theory by Silfurstar

Please accept that this interpretation/theory of "the light" will be mostly spiritual and symbolic. If you're looking for science, you will not find it here. But I will not push that aside without tackling it, so here's the first part of my interpretation :

1. It can't be scientifically explained for now.

A lot of things in life, until they are fully explained by science, remain quite mysterious and intriguing. Even science says that the explanation only holds until a better one comes up.

How would early humans interpret and consider the sun ?
How would they respond to magnetism ? (which has been tackled on the show in "Across the Sea")
What concrete explanation would they come up with to understand fire ?

Even now, aren't we still debating about the existence and meaning of the "soul" ?
Maybe that will one day be concretely explained by science, for now it isn't.

For me, "the light" is one of those things, so mysterious and hard to comprehend, that science wasn't able to explain it now. The difficulty to access it doesn't help either, no scientific community, except for the Dharma Initiative, got to study it. We saw the problems Dharma had to deal with, just to get to the light (drilling causing deaths, etc.).
It's no wonder that it cannot yet be explained.

So, what do humans do when they don't have an scientific explanation ? Either they ignore it, or they theorize, interpret, maybe give it a spiritual meaning.

The speech Mother gave to Jacob, about "the light" being in everyone of us, representing birth, life, death, rebirth, the whole cycle of life and reincarnation held dear by the show, was an interpretation, a theory.
The most important part is that they believed in it.

Would everything have ended if Jack hadn't put back the cork, life as we know it and all that ? Maybe, maybe not. Maybe they were wrong, and it would only have released such energy that the island would have sunk, or just shook for a little while and that would have been it.
But they believed it would end it all, so they fought for it (or against it, as far as the Man in Black in concerned).

The sounds and visuals attached to "the light", to me, suggest that it is not just a "spiritual" incarnation of something, but that the energy is very real, and probably worth a scientific explanation some day (once science reaches the point where it can explain it). The whole show suggested that, even the sounds the "black smoke" did when it moved around.
For now, it will remain (as some other things in life are) unexplained and mysterious.

2. The spiritual argument.

First, I'd like to clear up the fact that even if my interpretation is very spiritual, metaphysical and probably a little religious, I'm not and I will never suggest that they were dead the entire time of the show, as some other theories suggest.
For me, Island = life / Sideways = death, just so we're clear. I will suggest, though, that life is just another part of existence, as is death, etc. and that they all flow one into the other.

So, with that in mind, what does "the light" represent, and how do I interpret Mother's word to Jacob, in light (uh-uh) of what we have seen throughout the show, and last night's Finale.

All this time, Lost was about the bond that these character created and shared. Their lives before the crash were intertwined by coincidence or fate, and they all ended up on that plane, by Jacob's doing. On the island, the "most important" time of their lives, they all took on a journey to find a meaning to their existence, forgiveness for their past actions, a miracle that would cure them, or even love. Together, even when they were fighting against one another, they linked themselves to one another, a bond they would keep on sharing even after death.
"The light", which exists in everyone of them, represented that bond. From birth, to life, through death to the afterlife (or rebirth), they were meant to be together and take on this journey as a group, trying their best to do even better each step of the way.
The symbolism of magnetism here is strong. A force that attracts them all.

But another symbol that was quickly dismissed during the last season but which stuck with me for some reason, was the "lighthouse". To me, "the light" also works as a lighthouse, to be sure everyone finds their way back to were they are supposed to be, with the ones they are supposed to be with.
Even the "lamp post", the station that allowed them to find the island, has a "light" symbolic to it.

I could go further and remember the effect of "the light" on Desmond during season 2-3, or on everyone in season 5. May it be in space or time, "the light" always brought them where they were supposed to be, so that in the end, they would be in the right place. Desmond saw his life "flash before his eyes", and thus was set in the motion that would bring Penny and himself together again. Sawyer found love with Juliet, and so on...

If "the light" goes out, everyone is "lost". It would be impossible to find your way, nothing would bind you with your "soulmates" (not necessarely in the romantic sense of the word) anymore. That's what made it so important.
Without this light, it would not have been possible for them to meet in the afterlife, and they wouldn't have been able to "leave".
Maybe there really is a light at the end of a tunnel, once you die. At it will bring you to the one you love, the people you are linked with, that are waiting for you. And once you're all together, you can remember, let go, and move on.

There you go. It might not be a very concrete theory, there's probably some holes and it might not explain everything we've heard or seen about this mysterious "light", but somehow I find some peace by believing in this interpretation and my own vision of the show.
Turns out Charlotte was right, this place was death. But it was also birth, life, and rebirth. Death was only an inevitable outcome (sometime or another), and it was just another part of the journey they all shared.

Tell me what you think and don't hesitate to discuss it !
Thank you for reading (and sorry for my english, as it is not my first language).