Even dressed all in black, Hermann Nitsch looks remarkably like the Santa Claus of childhood imagination. Short and stocky with thinning white hair, full beard, and mustache, he needs only the fur-trimmed red suit to complete the perfect impersonation.

However, appearances couldn't be more deceiving. The 66-year-old Austrian artist, subject of a condensed retrospective exhibition at the Slought Foundation, would make even a mythical Santa shiver in his shiny black boots.

Nitsch (pronounced "Neetsh") is renowned as the impresario of simulated pain and death, the creator of elaborate orgiastic rituals based on mock crucifixions that involve the pouring and drinking of gallons of blood, the disembowelment of animals, and the frenzied fondling of their entrails.

Yes, the show sounds depraved, but don't reject Nitsch's art out of hand or judge it harshly until you've seen it. And you should see it; after all, Mel Gibson's film The Passion of the Christ was almost as bloody and far more violent.

One of the founders of the performance movement known as the Viennese Actionists, Nitsch has been jailed three times in his native country for pornography and blasphemy.

After you see the videos at the Slought Foundation that cover 40 years of his performances, you should understand why the Austrian police arrested him. (You can't look in the front window, though, because the gallery has installed a curtain to block the view.)

Devout Christians should be shocked and possibly disgusted by Nitsch's blood-soaked crucifixion reenactments, particularly by the way he links sexuality and suffering and his use of animal carcasses as Christ figures.

Sensitive souls might be put off by the killing of lambs, pigs and steers and their subsequent disembowelment in the service of Nitsch's carefully choreographed rituals. And then there's the smearing, pouring and drinking of blood - all from animals, but definitely not for the squeamish.

Nitsch has staged variations of his "black mass" more than 100 times since the early 1960s, most recently at his baroque castle at Prinzendorf, north of Vienna. There, his "actions" are staged in a spacious outdoor theater, seen in some of the videos.

The exhibition, organized by Slought's senior curator, Osvaldo Romberg, consists of a half-dozen video programs, two of them large-screen projections. Several programs are compilations that sample performances from all phases of Nitsch's career, while the others record specific events, particularly a six-day affair at Prinzenburg in August 1998.

Romberg believes it's important for Americans to become familiar with a strain of European art that, like Nitsch's work, is grounded in philosophy, anthropology, sociology and mysticism.

The so-called Happenings staged by American artists during the late 1950s and '60s (the term was coined by artist Allan Kaprow) resemble the Viennese "actions" only superficially.

Kaprow and his contemporaries were influenced by dada and surrealism. Their events were often lighthearted and whimsical. By contrast, Nitsch and contemporaries such as Rudolf Schwartzkogler, Otto Mühl and Gunther Brus were not only more ontological but often macabre.

Nitsch, who came to Philadelphia for the opening of his exhibition, explained in an interview that his art "has a lot to do with finding a new religious feeling. I believe in the whole creation, in our great nature and being."

The core of his art, he said, is intensity. "It's very important. Most people don't live intensely, they're more concerned with fashion," Nitsch said.

"I have a vision of pain in Christianity, there's a deep aesthetic for pain here. This kind of aesthetic I like, because it brings me very deep into the mysteriousness of being, of life and death."

Nitsch observed that Kaprow once described him as "the Grünewald of Happenings," a reference to the German Renaissance painter Mathis (or Matthias) Grünewald. His Isenheim Altarpiece, whose central panel depicts a Gibsonesque crucifixion, is one of the most stirring and famous works in European art.

"I grew up in the Christian tradition, and from this I go back to the root of all religions," Nitsch continued. "I'm doing religious archaeology," he added, citing Carl Jung's theory of the collective unconscious as an important stimulus.

Nitsch said he admired the intensity of Greek tragedy, "but I want only the intensity of it."

Regardless of what else you might think of it, his art is certainly intense, even when experienced secondhand through video recordings. Especially on the larger screens, the pageantry and ritual of what Nitsch calls his "Theater of Orgies and Mysteries" is captivating, at least initially.

Besides recruiting the dozens of performers that appear in these events, Nitsch also composes music that's played by a small band while the various blood rituals are carried out.

The young performers - one might characterize them as acolytes - are dressed all in white. Why? "Because the blood shows up better," Nitsch quipped.

The earliest videos, in black-and-white, seem more frenzied and orgiastic than the more recent ones, which by comparison are stately and ceremonial. Yet, over time, Nitsch's inversion of traditional religious ritual is a constant, along with a subliminal eroticism. Sex organs receive a lot of attention, including dousing with blood.

The crucifixion of Jesus is a central motif, with nude young men and, in one case, a woman, standing in for the Christian savior. Nitsch doesn't program (or at least doesn't photograph) overt brutality or cruelty; most of the actions are symbolic.

Some of these, such as pouring blood into the mouths of the Jesus surrogates or grappling bundles of slippery intestines, will certainly strike many as disgusting or perverse, like a few seconds of ritualized sexual intercourse in an early video.

However, the intensity of these actions, which one presumes the participants must experience to some degree, stops at the audience interface - that is, at the screen. Watching these recordings is primarily voyeuristic, because the viewer's experience is denatured.

It's nothing like participating in a religious service of any kind; the intensity comes across as an intellectual conceit more than as the desired emotional catharsis. Ironically, the only authentic emotion one may experience in these circumstances is revulsion.

One admires Nitsch's dedication to restoring primal emotion and authentic experience to modern life. For the most part, citizens of industrialized societies do live on the surface, finding relief from the anxiety and pressure of salaried drudgery with banal entertainments.

Perhaps that's why fundamentalist religions of all genres have attracted so many adherents in recent years.

Nitsch has at least described the problem of anomie in gruesomely graphic terms. However, his solution doesn't satisfy because, unlike true religions, his "actions" lack deep, authentic psychological roots and fail to satisfy emotional needs. While Nitsch is trying to revive prehistorical atavism, viewers of this retrospective are more likely to consider his blood-soaked "actions" bizarre, blasphemous and exhibitionist.

And in a final irony, there's so much real violence, suffering and depravity in the world these days that Nitsch's attempts to shock people into connecting with primal Jungian feelings seem almost quaint, rather than merely confrontational or outrageous.

Art | Old Blood and Guts

"Hermann Nitsch: Actions, 1962-2003" continues at the Slought Foundation, 4017 Walnut St., through May 19. The gallery is open from 1 to 6 p.m. Wednesdays through Saturdays. Information: 215-222-9050 or http://www.slought.org/.