Porn rakes in billions of dollars a year without anyone ever admitting to watching it. In “Don Jon,” his debut film as a writer and director, Joseph Gordon-Levitt plays a sexually voracious guy who very well could be propping up the entire porn world himself.

Gordon-Levitt stars as Jon, the kind of guy who would fit right into MTV’s “Jersey Shore”: a hunky, swaggering, not-too-bright fellow who each night brings home a different girl from the dance clubs he frequents. The problem is Jon loves watching porn even more than he enjoys hooking up, rolling right out of bed after his sexual bouts with strangers to surf the Web for ever weirder ways to get off.

This might sound like a creepy and gross subject for a film, but don’t worry. Gordon-Levitt has built a thriving career by taking chances with top-flight directors in such intelligent films as “Inception,” “Looper” and “Brick.”

In his clever and surprisingly touching vision, Jon isn’t just a hopeless pervert akin to the character Michael Fassbender played to great critical acclaim in 2012’s “Shame.” Rather, he’s a humorously conflicted but devout Catholic who prays while working out and frustrates his parish priests with his weekly confessions.

Jon treats confession as a carwash for his soul, racing to church every Saturday afternoon to cleanse his spirit in time for Sunday Mass, yet inevitably lapsing back into a staggering number of sexual sins throughout the next week. But when he meets a stunning woman named Barbara, played to sensual and comic perfection by Scarlett Johansson, he finds himself forced to change because she finds porn disgusting and makes him swear he won’t ever watch it again.

As Jon matures into monogamy and wins his battle with porn addiction, the impact ripples out across his confused friends and bemused family. He also finds himself taking a night class in college for the first time at Barbara’s behest, and there he meets a sad, middle-aged woman named Esther (Julianne Moore), who keeps trying to be his friend even as he pushes her away, thinking that the only woman he’ll ever need is Barbara. And of course, there’s Jon’s hilarious quest to receive a lesser penance of prayers in confession each week as he improves his behavior.

From that crossroads of growth in Jon’s relationships, Gordon-Levitt weaves a sweet, funny and emotionally stirring tale of a simple guy trying to make sense of a life he realizes is stuck in shallowness.

“Don Jon” impressively walks several tightropes. The movie must show the allure of porn for Jon and the millions of other men just like him — a sexual experience that seems hotter and better than anything a real woman could ever give them – while also conveying its real message: that pornography not only degrades women, but also the men who watch it.

In pursuing that point, Gordon-Levitt and ace editor Lauren Zuckerman rev up some torrid montages of naked women performing acrobatic sexual feats while still making the images empty and ultimately sad. On the other hand, once the movie settles into its real story of the conflict between shallow sex and impassioned true love, Gordon-Levitt and his lively costars (including a terrific Tony Danza as his profane lecher of a father), the story becomes a wise and romantic tale that women will also love.
With those conflicting elements woven perfectly in sync, “Don Jon” recalls the 2005 hit “The 40 Year Old Virgin” as a film that appears to be a raunchy romp on the surface yet calls for greater decency in our debauched times. That’s a message that’s welcome from anyone in media, and here’s hoping that Gordon-Levitt keeps finding valuable things to say while entertaining audiences in future projects.