One afternoon in theology class, his professor riffed about a case of demonic possession that had recently occurred in the Washington area. Something about it struck a nerve.

“I remember thinking, ‘Boy, if somebody would dig into this and authenticate it and show that it’s the real thing, what a gift to the faith,’ ” Blatty says. “It stayed in my mind, and I thought maybe someday I’d try to write a nonfiction account.” – from an interview in The Washingtonian

There is probably no book from the mid-twentieth century heyday of Catholic literature that is more widely misunderstood than The Exorcist. At first blush, it’s easy to see why Catholics would want to shy away from a story that includes a scene of a young girl being forced by a demon to masturbate with a crucifix. The film adaptation was so nauseating that theaters began handing out barf bags with ticket purchases. It’s not the sort of first impression that screams, “True, beautiful, and good.” But from the moment it was published in 1971, The Exorcist was hailed as an instant classic in company with the works of Mary Shelley and Edgar Allen Poe. The book has sold over thirteen million copies and, adjusted for inflation, the 1973 film adaptation remains the highest-grossing horror movie of all time.

William Peter Blatty was clearly onto something. But was it shock and shlock, or something deeper?

The critics of the 1970s were not equipped to accept the story at face value. Here they were confronted by a book-turned-movie that explicitly probed the nature of good and evil, the relationship of science and spirituality, the war between God and the Devil—and it was written by a man whose previous success had been as a Hollywood comic who wrote punchy one-liners. Critics who took its religious elements seriously decried them with jaded cynicism. “[I]t treats diabolism with the kind of dumb piety movie makers once lavished on the stories of saints,” said Vincent Canby of the film version in The New York Times. Pauline Kael of The New Yorker called it, “the biggest recruiting poster the Catholic Church has had since the sunnier days of Going My Way and The Bells of St. Mary’s.”

At least Kael understood it. Other critics quickly coopted the power of the narrative to suit their own political agendas. “I’ve read some of the most ridiculous theories, even by critics that I respect, about how the novel symbolizes teenage rebellion and all sorts of sociological nonsense,” Blatty says. “There’s no hidden message. The book is the book, and it says what I wanted it to say.”

What did he want it to say?

“It’s an argument for God. I intended it to be an apostolic work, to help people in their faith. Because I thoroughly believed in the authenticity and validity of that particular event.”

The Exorcist is a book based on truth—a real case of demonic possession that took place in 1949—that seeks also to explore the deeper Truth of our human need for God. If you are willing to steel your mind and stomach against its grotesque portrayals of genuine evil, what you can find in The Exorcist is a book full of surprisingly rich prose built on a sound foundation of Catholic theology.

And yet from this – from evil – will come good…. Perhaps evil is the crucible of goodness. And perhaps even Satan – Satan, in spite of himself – somehow serves to work out the will of God.

The Exorcist gives us one of the great dramatic portrayals of felix culpa, the idea of the Fortunate Fall. As St. Augustine expressed it, “God judged it better to bring good out of evil than not to permit any evil to exist.”

I think the demon’s target is not the possessed; it is us . . . the observers . . . every person in this house. And I think—I think the point is to make us despair; to reject our own humanity, Damien: to see ourselves as ultimately bestial; as ultimately vile and putrescent; without dignity; ugly; unworthy.

The demonic presence attacks the essence of human dignity in order to drag people into despair. And its evil can only be fought with despair’s opposite: Hope in the saving grace of God.

We mourn the blossoms of May because they are to whither; but we know that May is one day to have its revenge upon November, by the revolution of that solemn circle which never stops—which teaches us in our height of hope, ever to be sober, and in our depth of desolation, never to despair.

Ray Bradbury said, “[The Exorcist] is a great love story. I wish I had written it.”

For my part, I am merely glad to have read it.

Karen Ullo is the author of two novels, Jennifer the Damned and Cinder Allia. She is also the managing editor of Dappled Things literary journal and a regular Meatless Friday chef for CatholicMom.com. She lives in Baton Rouge, LA with her husband and two young sons. Find out more at www.karenullo.com.