With time, the initial shock and horror of The Exorcist’s images has subsided for me and I appreciate the real underlying story.
This film is about faith. Do you have the inner faith within yourself to overcome evil and live in the light and good? Or, do you struggle with faith and open yourself up to evil?
Religion is not necessary. An understanding of good and evil will suffice along with the inner strength you need to embrace and accept faith that will be your salvation. The main character here is Father Karras. His struggle is all of our struggles. You want him to believe and to find the strength. He is human. He is flawed. He doubts. But, he sacrifices for the fight of good vs. evil.
That is the take away from this film to last a lifetime.