6. Why Did Regan React To Tap Water? (The Exorcist)
Part of the demons modus operandi in The Exorcist was to engage with Father Merrin (Max Von Sydow). In one of the early exorcism scenes Father Karras (Jason Miller) throws tap water at Regan (Linda Blair) saying it is holy water. The demon reacts in pain then Karras tells it that it was plain tap water implying Regan is not possessed and its a mental health issue. This reaction could be taken two ways. The demon wanted to interact with Father Karras and thought if it reacted to things like Holy Water Karras would be convinced of the possession. Conversely, the demon could have been playing along as its real fight was with Father Merrin. The demon, wishing to get rid of Karras faked the reaction in order to speed up the process of getting Father Merrin involved. Demons, they know what they want as much as women do.