The deceptively simple story, first realized by William Peter Blatty’s 1971 bestselling novel and later in his faithfully adapted screenplay, is almost a straight line of brutal narrative efficiency. A sweet, innocent little girl named Regan (Linda Blair) is the child of a messy secular marriage when she begins behaving strangely, and then demonically. The doctors say she has a brain lesion, but that seems like the wrong diagnosis when she can speak in reverse and move her bed and furniture off the ground. Her desperate mother (Ellen Burstyn) seeks the help of the Catholic Church, and eventually a young and an old priest appear, willing to give their lives to free Regan from an evil spirit proclaiming itself to be the Devil. The directness of The Exorcist is why it has been copied, mimicked, and built upon a thousand times over the years. It’s also the reason that in just as many decades, none captured the public consciousness in the way that this film did. Opening on Dec. 26, 1973, just one day after Christmas, The Exorcist became a cultural phenomenon. Earning more than an ungodly $200 million in the U.S. during the winter and early spring of 1974, the movie grossed over $950 million when adjusted for inflation (meaning that it sold more tickets than Star Wars: The Force Awakens). It’s an entertainment so grotesque that it still crosses the line of decency four decades later, and yet it tapped into a pop culture zeitgeist that’s almost unheard of by modern audiences. Blatty, a product of Catholic upbringing and a Jesuit education, crafted a story meant to diagnose evil in quantifiable terms for an increasingly apathetic society. Or, in other words, he sought to bring secular readers closer to God by literally scaring the hell out of them. Conversely, William Friedkin, the director of The Exorcist, is a self-professed agnostic of Jewish background and a through-and-through cynic. Thus when landing the chance to adapt a bestseller that studio heads viewed along the lines of a Universal monster mash, the eternal provocateur decided to push the material to the point where even he could understand the desire to seek spiritual aide from the Catholic Church. As a result, this offspring of a believer and a skeptic became a master class in rationalizing turning to God when faced with the visage of genuine evil. More than horror, The Exorcist is a forbidden journey into the many variations of human despair, enveloping the viewer with a melancholy so indescribably merciless that it pervades almost every frame, even the ones without demons subliminally inserted in the corners. Instead of aiming to charge audiences with the methodically patented “scare” or false jump at each 10-minute mark, The Exorcist lingers on mankind’s depravity, and in its many forms, for over an hour. Just as Friedkin used the ravages of an impoverished New York City to inform his seedy 1971 criminal masterpiece The French Connection, he returns to the (then) slums of Lower Manhattan as one of his many devices for world-building. With the patience of a period piece storyteller, Friedkin wants to stare into the abyss of the human condition long before he has the Devil glaring back. read more: The Best Modern Horror Movies While the film’s other lead character, Burstyn’s Chris MacNeil, comes from the more gilded confines of wealth and success as a Hollywood movie star—because it’s not a 1970s American film without some kind of navel-gazing—her initial comfort means little when her 12 year old daughter begins demonstrating signs of schizophrenia or a myriad of personality disorders. Friedkin chronicles the soul-crushing misery of one failed medical test after another. The modern tradition of horror films is to place its heroes and heroines in a middle class existence for maximum relatability, but the direness of Chris and young Regan’s situation is only compounded when even the best doctors money can buy can’t find a solution. Indeed, the gloomiest image of the whole movie arguably could be a doe-eyed 12-year-old trapped under a seeming half-ton of medical equipment with no hope of salvation in sight. Rather than ratcheting up the scares, The Exorcist piles on the hopelessness of existence by documenting with a procedural’s exactness the ugliness of life. Only then, once we see our own sorrows in Chris’ plight, or Father Karras’ crisis of faith, does The Exorcist choose to truly enter the supernatural and crawl under your skin, wearing it and your anxieties like a cheap suit days after exiting the theater. With every set-piece calibrated to demoralize the viewer, the mood is far more debilitating than the oft-used ominous and crashing musical tones of other religious horrors. The result is an audience as hollowed out as Chris when the Devil’s presence in Regan becomes undeniable. Despite the demon’s pervasive powers in Blatty’s novel, one needs only to look at Roger Ebert’s 1973 review to see contemporary readings wanted to consider The Exorcist novel as an ambiguous tale about possible mental illness. Friedkin robs skeptics of that security blanket in the film. Using every filmmaking tool in his arsenal, including coarse language coming out of a child’s mouth, repugnant make-up that still churn stomachs, and shock “scares” as abrasively over-the-top as spinning heads and green vomit, there is no room for intellectual doubt during the cinema’s most visceral and most savage bombardment, nestled uncomfortably in a young girl’s bedroom. read more: The Best Horror Movies to Stream The solitary difference between the grossness of The Exorcist and modern splatter fest tactics, such as the torture porn fad of the previous decade, is that The Exorcist wants to make a point that is meant to refute casual indifference. The most repellent scene in film history may very well be when Blair’s 12-year-old victim is depicted as taking a crucifix and repeatedly stabbing it into her vagina to the point of bleeding, screaming “fuck me” while she does it. The juxtaposition of a young girl’s womb being mutilated by the symbol of Christianity is the literal and intentional visualization of blasphemy made flesh—two things meant to represent the utmost purity being irrevocably desecrated upon their meeting. At that point, there is no turning back for Chris or the audience: her daughter is the Devil, and Chris must find God. When the audience clings to Max von Sydow’s kindly Father Merrin, entering the picture during the third act as the film’s first moment of optimism, it has already achieved its goal. The actual downbeat ending that comes later just reconfirms to Chris, Regan, and the audience that what went on in that bedroom was reality, and its abiding terror is likewise all too real. read more: Best Horror Movies on Netflix A horror movie taking on such an omnipresent life after its opening seems alien in the age of frontloaded weekend turnovers where the horror genre is the stuff of “micro-budgeted” in-and-out fast food affairs. The Exorcist instead haunted moviegoers for months (or their whole lives). It went on to win Blatty an Oscar for his screenplay and earned nominations for Best Picture, Best Director, and a slew of nods for cast members Burstyn, Miller, and Blair. The levels of depravity aspired to both onscreen and off during the making of the film are also legendary, with the many stories of Friedkin firing a gun in Miller’s ear to obtain the right look of fear, slapping real-life priest Rev. William O’Malley in the face during filming, and permanently (and cruelly) injuring Burstyn’s back on-set by dangerously abusing a harness pulley. However, the reason the movie is truly scary is that it was all done in the name of a sensation other than fleeting horror. Watching The Exorcist still conjures up the feeling of looking into shadows that should remain unseen. It longed to instill hope for something better in this life, even if by literal gunpoint in the case of Jason Miller. That it miraculously accomplishes this while staring into that blackness, and finding what stares back, is why The Exorcist still scares today. David Crow is the Film Section Editor at Den of Geek. He’s also a member of the Online Film Critics Society. Read more of his work here. You can follow him on Twitter @DCrowsNest.