It is perhaps not fair to review "Nymphomaniac: Vol. 1" separately from "Vol. 2," which hit video on demand Thursday and opens in theaters April 4. This really is half of Lars von Trier's opus about a sex addict.

But this four-hour movie is being presented to audiences in two-hour halves. So with the serious caveat that "Vol. 2," which I haven't yet seen, could change things, honesty compels me to acknowledge that "Vol. 1" is a fascinating but meandering mess.

This first part is a bold and earnest effort with fearless performances that never objectifies its protagonist.

It's also a jumbled concoction of grandiose philosophical ideas, connoting sex addiction with the art of fishing, Fibonacci numbers, tritones and other theoretical conceits, set to a theme by Rammstein. Like so much of von Trier's divisive oeuvre, it believes so wholeheartedly in its own profundity that the enterprise comes crashing down.

The film has gotten a lot of attention because of its unsimulated sex scenes, which are in fact digital mash-ups of the onscreen actors and porn actors' privates.

"Vol. 1" couldn't be less erotic, though. It is, instead, a joyless deconstruction of female sex addiction written and directed by a man who clearly knows nothing about women. How else to explain a scene in which our young protagonist, named Joe (Stacy Martin), and a friend stage an impromptu competition to see who can have sex with more men on a train, with a bag of chocolates as an award?

The movie is narrated by Charlotte Gainsbourg, playing an older version of Joe who has been mysteriously beaten and left in an alley near Stellan Skarsgård's building. Rescued by Skarsgård's Seligman, she dissects the first stage of her long trudge through nymphomania, which includes loveless sex with dozens of men and an enduring affinity for the enigmatic Jerome (Shia LaBeouf).

Seligman pops in with the aforementioned analogies, helpfully illustrated with giant numbers flashing onscreen as Joe loses her virginity and cutaways to fishing lines being cast to sea and the performance of a symphony.

In other words, his character functions to pad out von Trier's thin, arid conceit, giving it the veneer of intellectualism. Unfortunately, in a fashion that reflects "Vol. 1" as a whole, he's got nothing of particular interest to say.

Nymphomaniac: Vol. 1
Directed by Lars von Trier
Starring Charlotte Gainsbourg, Stacy Martin, Stellan Skarsgård, Shia LaBeouf
Rated NR
Playing at Landmark Sunshine and City Cinemas 1, 2 & 3 and on VOD