My Problem with the Ending
Just my thoughts on the film, and particularly the "twist" at the end.
I thought that until the ending, this was an absolutely terrifying, yet very intelligent horror movie. The theme of religious delusion taken to an extreme - and passed on to young children (aka Adam) who can't know any better - is chilling. The fact the Bill Paxton's character thinks he is doing Good, and forces his children to be complicit, while being objectively insane, is what makes this so disturbing.
Now towards the end of the film come two surprises (from my understanding on 1st viewing):
1) the grown brother telling the story is actually Adam, who has continued his father's legacy of killing demons, and is using this as a means to capture the FBI guy, his next victim.
2) And here i where I have a problem - we are SHOWN (for the first time) the vision of the "demon's" evil doings, which are then CONFIRMED by the FBI guy. In other words, we are pretty much being told that the Demons are real, and that father and son are following God's Will.
There is little ambiguity here - we even get flashbacks to the father's "visions" - now apparently only not shown before to preserve the "twist"...
Basically, I found this left turn to be very ineffective in that it goes against the feel of the whole rest of the film. Frailty has been showing us religious fanaticism, and remained grounded in reality - even Paxton's vision of the angel is filmed in a way that strongly suggests it is taking place in his mind. But at the end, the story's narrative swerves into the supernatural, telling us: "TWIST, The Father WAS killing demons all along...". By this logic, not only is this (to an extent) justifying the killings we have witnessed, it is also just a plain ridiculous direction for the film to take: both to me, as a non-believer, from an external perspective, but also by the film's own inner logic, contradicting established tones and themes. In other words, the film shoots itself in the foot a little.
Final thoughts: I'd almost like to think that despite these points at the end, there is still enough ambiguity to think that there was objectively no Hand of God or Demons...however the film just seems to tell us otherwise. Lastly, even with this twist, the ending (Adam just a regular all-American guy just like his dad...) is still disturbing - as if the filmmakers wanted to leave us with the tone they have established for most of the film, if only they hadn't somewhat sabotaged it towards the end...
Thoughts? Please let me know if you think I'm reading something wrong, or disagree, anything! :)