I [i]knew[/i] those things were demonic! [b]The Following[/b] proves it.
That Easter egg of the Volatile rally behind the door on one of the last missions (of the original game), shows that they have some sort of consciousness.
The little cave below the mountain shack where you have to find some herbs (The Following), that thing was a glimpse of hell, and the volatiles were part of it. The screaming and demonic whispers too.
Then the ending of the [b]The Following[/b]...hooo boy... that sealed the deal right there. Volatiles are reincarnated demons
-
[spoiler]what about crane and the mother, they aren't demons just got the body of a volatile [/spoiler]