I am glad this thread exists. It give me a chance to chime in with my theories here. I feel it appropriate for myself to write this, because I believe I have written other threads that will be taken as myself being an Alan Wake hater. Well, it had been critical to some degree, more of the hyping being done than anything else. Anyhow, this being said, I need to add here that I don't have the game, nor did I play it, BUT I will say this semi-confusing statement that if the game and world is as I think it is, it is EXCELLENT writing that makes the game a psychological thriller and one I will need to get sometime and own and play through. My story with the game starts last night where I stumble across the product placement and then wanted to learn more about the context there, which then led me to the ending... which I watch on YouTube. I then read all the theories, and ended up developing my own. So, here is my take on this:
For me, the key to understanding all this is the line "but an ocean". This is in reference to the lake, and was written by Alan Wake. So, as I see it, Alan Wake has just turned the lake into an ocean by writing it. He let the Dark Presense have its way. One has to wonder why one tries to contain the darkness. But, what came out from it was that he needs to take the journey into darkness, so that the darkness grows, and he has to then battle it with light, so that good comes about. He writes that he knows the equation must be balanced, which meant that there are sacrifices involved. This is said of maybe evil making a bargain, but then he realizes the inverse. By letting the darkness grown, the battle gets waged, and you shine a light on it, and good comes about.
The lake is supposed to be a source of great magic, and make what the artist creates reality. This art of creation can be used for good or evil. What I see the evil presense is, is that part of man which is the darkness. It is the evil parts that drive men to do bad things, and it is also the unknown and disasters that men thing on. It is actually what exists in the unknown. Alan narrates how there is an equation and a price that must be balanced, like it is a law. When he realizes this, the way he is able to see the ending that happens in Bright Falls is to give himself over to the darkness, and then allow the light to shine. Don't fear the process of being a creator, but battle the darkness, for that is what all great stories do have. You go deeper into the darkness and shine a light on it. You don't attempt to bury it, but let it run its course.
And all this, to me, is excellent, and lends to why I need to get this game. This IS a psychological thriller, and not just some horror movie. It is about the mind and nature of man, and that explaination really hints at great storytelling. Anyhow, maybe I am off, but that seems to make a lot of sense to me. Please feel free to correct anything I say, as I have not played the game yet, but did read up on the plot of the game, and the characters, and the explainations and I did see the game.