Scientology is really no goofier in its belief system than are any of the world’s major religions, with their virgin births and reincarnations and, yes, talking donkeys, but it seems predatory toward its adherents in a way scary cults are. Will it ever grow past that? As Alex Gibney’s broadside on the church of Hubbard and Travolta and Cruise prepares to air on HBO, the great Tom Carson writes of the anti-auditing doc at Grantland. An excerpt:

The church’s own claims of around million members aren’t what you’d call reliable, and that’s still a drop in the bucket to Vatican City and Mecca. But ex-insiders estimate the actual figure is a paltry 30,000 adherents worldwide. If so, Scientology’s prominence as an alternative faith and/or perceived public menace is some kind of tribute to Hubbard’s Warhol-anticipating perception that celebrity is currency; according to the same sources, one out of six of those 30,000 live in Los Angeles.

Another measure is staying power, which in this case is still TBD. It’s been only 60 years since founder L. Ron Hubbard ginned up a mental-health program into a mighty — let’s be polite — idiosyncratic theology. Remember, though, that a new creed’s apparent preposterousness is no guarantee of failure. In the first century A.D., Christianity’s tenets probably sounded fairly goofy up against the more plausible stuff about Jupiter, Minerva, & Co. that the civilized world swore by. At least in theory, it’s totally possible that sociable chat about thetans and Suppressive Persons — the jargon Hubbard bequeathed us — won’t be any more outlandish a few hundred years from now than being down with transubstantiation or the virgin birth.

Porky Pig turning drone may seem more likely, but whatever you think of the prospect, the day is brought no closer — and that’s putting it kindly — by Gibney’s harsh and sometimes blatantly alarmist doc. Its full title is Going Clear: Scientology and the Prison of Belief. Gibney’s take derives considerable authority from being based on prizewinning New Yorker writer Lawrence Wright’s scrupulously reported book of approximately the same name. (Wright’s subtitle had “Hollywood” in there, too, and it would be interesting to know what prompted the elision: The doc certainly features enough of John Travolta and Tom Cruise.) But so long as we’re talking the difference between religions and cults, try to imagine HBO running a comparable documentary about, say, Mormonism — in more ways than one, as Wright’s book details, Scientology’s 19th-century equivalent, at least in the popular suspicions (and derision) it aroused when it was founded.•