You're the one being stupid with your rash generalizations and inability to properly analyze a film.
A supernatural explanation doesn't make the film stupid, and the two answers don't have to be mutually exclusive. Simon can be an entity that possess people through a process similar to one going mentally insane. This raises the film's central question and main point of ambiguity: Is possession real or is it mental illness? The fact that film provides you with this question is proof of it being multi-layered.
In the end, trying to simply figure out which is which for the purpose of tying a neat bow on the narrative just does the movie a disservice and ignores the subtleties of the film. Would you prefer a flat picture, with an explicit answer and nothing to analyze and question, or one that provides a certain level of ambiguity that can be discussed and analyzed via the various layers provided? Because when you say you have a problem with people thinking the other way, then one would think that you would prefer the former.

Mike wasn't an idiot. He was doomed to die also, because of his potential to figure out what's going on. Thus the reason the entity killed him. Plus the Session Tapes were easy to find, so perhaps the entity was playing cat and mouse with Mike until the end.

I think the film is interesting and haunting
because it is ambiguous
. There is many possible readings, including a supernatural element. There are a lot of coincidences that could point that way, like when Gordon hurts himself while the recording is about a knife, or how he uses Mary's room, sits on her tomb when Mike sees the number of her file, etc. I don't think the director wanted it to be clear-cut : supernatural or not, horror or not. Maybe the place isn't haunted, but Gordon is haunted by the place, it triggers something in him, something that was already building maybe, but that expresses itself there.

Mike listening to session 9 was not a threat to Gordon because Mike didn't know his life was in danger and that Gordon had killed Hank or his wife.

Everyone is in a vulnerable position when the generator goes down, and that's the common denominator. Session 9 is never heard because the generator goes down. Two of the men were in tunnels when the generator goes down as well.

No one dies when the generator goes down, Mike goes out and re-fills the generator, the generator comes back on and the kid walks out to the van, I suppose you could argue about when Phil is killed. He kills everyone after the generator is back on but it also happens to be after Phil confronts him about stabbing Hank.

Evasiveness won't help your argument. Everyone dies when the generator goes down. That's a big coincidence.

''
I don't see why people have such a problem with other people believing it was something supernatural like a demon, which is what I believe.
''
Personally, I always have a problem with people being stupid

Haven't watched this movie or been to this board in years, but I knew coming back here tonight I'd still find this argument going on. I don't see why people have such a problem with other people believing it was something supernatural like a demon, which is what I believe.
I just don't get why anyone would try to tell someone else what to think. You think what you want but allow others to do so as well.
If you love someone, set them free. If they come back, nobody else wanted them either.

I think it's interested how angry some people get about a supernatural interpretation. It seems pretty clear that a big part of what makes this film interesting is that the filmmakers deliberately leave room for interpretation. The movie isn't vague or pointlessly ambiguous but it does ask a few key questions of its audience and allows them to answer those questions for themselves.
I personally don't really understand how anyone can think that a little bit of ambiguity wasn't intended by the filmmakers. Especially given interviews in which they state they removed certain elements from the screenplay (like a homeless woman responsible for the creepy sounds), because the movie was more effective when they allowed for more interpretations as to what was really going on.
It's similar to the film Total Recall
SPOILERS!
Obviously that film's ending is meant to be ambiguous, presenting the audience with two possibilities (one being a dream and one being real life), but we're not ever meant to know the truth 100%.

I know this thread is old now, but the sense of realism is what makes this movie so friggin' scary. When I first saw this I was scared out of my mind.
I was actually paranoid that I might start hearing voices because I was going though a particularly tough time and could have been considered "weak" and it scared the bejeezus out of me.

"If Mike had listened to session 9, what would give him the idea that Simon supposedly possessed Gordon? "
Because Mike then would have had a choice as to whether he should leave the building or talk with the other crew members. He was listening to these tapes for a reason. Mike knew strange things were going on, and this would support a specific suspicion that the building is an unhealthy influence.

Am I missing something? If Mike had listened to session 9, what would give him the idea that Simon supposedly possessed Gordon? Mike didn't know he killed his wife. He only knew what Phil told him, the fake memory of Gordon hitting his wife because he was suppressing the memory of what really happened. What would make Mike want to escape after listening to session 9? I must be missing something. He couldn't have just come to the conclusion that Gordon was now possessed. What would give Mike the idea that Simon was an entity anyway? The doctor thought it was an alter made up by her own subconscious. If you are going to say Simon's voice gives it away, well that is not a valid argument because in real life some people with
DID/schoziphrenia can imitate a different voice auite well. They could have just made Simon's voice a real male to add to the spooky effect.
I still don't know how to interp this movie which is why I am reading theories to see which one makes the most sense. Your theory was good but there is no reason why Mike would have escaped after listening to session 9.

"but if you notice NO ONE IS LISTENING to the tapes when Simon starts talking."
This supports the theory that Simon is an entity, since Mike conveniently walks away without listening to Session 9 and then he's murdered. Had he listened to Session 9, he could have gotten out of the building and escaped. Another generator coincidence and supports a paranormal argument.

Not necessarily. I'm an atheist and I can entertain ideas of supernatural nature. It's called suspension of disbelief.

ARE YOU A PARTY ANIMAL?
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He's clearly a religious person and that's why he's drawn towards the "entity/possession" angle and not the psychological one.

I believe this is the point at which we arrive at running in circles. I'll keep saying the tape proves nothing because the player, once set to play, is only at the mercy of the entity called electricity. You will keep insisting that this somehow proves something completely unrelated to whether the player is receiving electrical power or not.
So could people on this board at least agree that viewers were baited by the director to believe that two theories about murder motives could be valid.
I believe I have stated this very thing on more than one occasion; neither premise can be entirely ruled out and, honestly, an argument could be made that both exist simultaneously.

This is just my personal opinion, but I think the point you just made above supports my premise that an entity is at work, or the writer/director wouldn't have included: Start tape.
Power out - Tape off.
Power on - Tape on.
I'm not trying to second guess your views, but filming the final session after the power came on was the chilling event found in most paranormal horror films. I'm not suggesting that there's anything wrong with people believing that this is a simple murder mystery with no evil entity, but so much is included in this film that leaves viewers with the impression that an entity is behind the voice.
So could people on this board at least agree that viewers were baited by the director to believe that two theories about murder motives could be valid.

That means nothing. Maybe the entity didn't care if the recording came on later
You misunderstand me. That no one was there to hear the Session 9 tape is a moot point. It's moot because the power went out when it had been set to play and would have automatically started once the power came on again anyway. that's straight cause/effect.
I'm not sure what you mean about an entity not caring; that's what was going to happen regardless:
Start tape.
Power out - Tape off.
Power on - Tape on.
This would occur no matter who was or wasn't in the room and would even occur with no one in the room so it really can't be used to validate or dispute anything.

Those arguing that no one was there to hear the Session 9 tape are conveniently forgetting that Mike went down there to specifically listen to it, had it set up and starting to play, before the generator issue removed him from the room. Of course the tape would continue playing from that point when the power came back on back on if it's already been set to do so; it isn't going to pause itself waiting for someone to come along and hear it.
That means nothing. Maybe the entity didn't care if the recording came on later, just as long as human ears didn't listen to it. Clearly enough evidence is written into the script for two reasons. Either an entity was the driving force for the murders, or the writer/director wanted the paranormal to be a STRONG possibility for audience theories. For anyone to suggest the paranormal is 'out of the question', is just being dishonest. period.

There is also the matter of Gordon wandering off in a daze and winding up sitting, spaced-out, at the potter's field. Inside, at that exact moment, Mike finds the Mary Hobbs file stamped with "Deceased #444" on the folder. We cut to Gordon talking on the mobile to what is presumably dead air (since it is later revealed what transpired at his home before this point) as the camera pans down and reveals an overturned broken grave marker right where he's sitting. The number on it? (Gasp!) 444.
People can argue dramatic effect all they like, this specific scene is just a little too convenient and too coincidental to imply anything but some sort of meta-connection to the events as they are unfolding in the narrative as opposed to some rather in-your-face symbolism.
In order to maintain the dramatic effect theory, it would have to be a tight knit and coincidental constellation of events placing him at the grave right at the moment Mike finds the file purely for the benefit of the audience. In order to push the theory that that Gordon had access to all the tapes and files and then incorporated them into his psychosis, one would have to ignore that we are shown Mike being the only one to find anything pertaining to Hobbs or insist that Gordon had unfettered access to them off screen (then also ignore that, even during the revelation of unseen events near the end of the film, any such scenes of Gordon having access seem notably absent).
Those arguing that no one was there to hear the Session 9 tape are conveniently forgetting that Mike went down there to specifically listen to it, had it set up and starting to play, before the generator issue removed him from the room. Of course the tape would continue playing from that point when the power came back on back on if it's already been set to do so; it isn't going to pause itself waiting for someone to come along and hear it.
As for the cut homeless woman, it was always intended to be a red-herring but they rightfully cut it because it would have disrupted tension. There is even dialogue by the security guard in the very beginning about how former patients would find their way back there because they had nowhere else to go. The audience was expected to assume events were being caused by a mentally disturbed prodigal patient before the narrative revealed, or at least inferred, otherwise.

THERE ARE NO GHOSTS THAT CUT POWER, just deal with it.
Why would the writers put this scene in a key location of the story line. You make no sense. Not to mention all of the crew members being in vulnerable areas of the building when the power goes off. It's amazing how much of this story line you ignore to support your own views. Still waiting for you to explain how all the coins got into the wall, and who would know this character would just happen to be walking down the hall. More story line you decided to ignore? Writers place this information into stories for a reason.

I avoided the generator thing because it just wasn't a proper argument. It is a dramatic effect, artistic element to bring up the atmosphere, and it eventually did nothingso why would it be important. Did all of them die during the blackout? Do you have any reason to believe the blackout is a work of a ghost?
As I said, power went down in my building just as I was walking down the stairsmore than once. Was ghost trying to kill me, again and again? Am I living in a haunted building?
What other unexplained coincidences?
I, on the other hand, am impressed by your attempt to sound all scientific in explaining to be 101 of brain function while using the ''unless possessed by an entity'' sentenceWOW! ''Entity'' does sound much more serious than ''ghost'' or ''demon''.
THERE ARE NO GHOSTS THAT CUT POWER, just deal with it.

But remember the generator going down right at a point in time when everyone in the building was in a different location and vulnerable. The down generator is also the reason Mike didn't get a chance to listen to Session 9. Way too convenient for the killer. Had to be demonic possession.