It's not clear whether Pullman himself actually believes in Dust or if it's just an effective plot device, but there's no doubt that His Dark Materials has the same effect on certain susceptible readers (say, me) as Avatar does on some moviegoers. You finish the Pullman trilogy electrified and desolate, heartbroken that the world can't be as he depicts it. Though Pullman is most often compared to C.S. Lewis and J.R.R. Tolkein, the author he may resemble most is Scientology founder L. Ron Hubbard. This is not a literary comparison—Hubbard was a pulp hack, while Pullman has written the most thrilling and imaginative novels in a generation—but we may wake up one day and find that Pullmanism has become a religion, that Dust has been made flesh.This is extremely bizarre. Now, I am not a fan of Pullman. Indeed, I think that the comparison to L. Ron Hubbard is apt not because Pullman is an evangelist for a new, crackpot theosophy, but because Pullman is a hack. His books are lousy. His prose heavy-handed. His adolescents intolerable. His "world-building" clumsy. I read those Dark Materials books at the urging of a friend. By the time I was at the rollerderby elephants (I am not making that up) on page umpteenhundred, I was ready for a quaaludes and Old Granddad cocktail.
But, I mean, it is clear that Pullman does not, literally, Joe Biden, believe in Dust anymore than C.S. Lewis believes in talking lions, Tolkein believes in orcs, Herbert believes in giant sandworms, or Asimov believes that Robin Williams was the right casting choice for the cinematic adaptation of Bicentennial Man. The fact that Pullman's books are insufferably didactic does not mean that he believes their fantastical elements to be metaphysically true. Pace my midichlorian count, it would be more accurate to say that George Lucas believes in the Force than to say that Pullman believes in Dust.
David Plotz himself wrote a rather insufferable little tome that I had the displeasure to read, The Good Book: The Bizarre, Hilarious, Disturbing, Marvelous, and Inspiring Things I Learned When I Read Every Single Word of the Bible, which is a sort of idiot's guide to the so-called Old Testament, in which our author stumbles googley-moogley-eyed through the savage histories of the ancient Hebrews, exclaiming at every opportunity that he never learned about all-ah-dem rapes-n-murders in Hebrew school, nosiree. Affecting the unsubtle guise of a complete moron and cryptoilliterate in order to éclater la bourgoisie is hardly a dignified position from which to subsequently sneer at atheists for their "emphatic and complicated religious beliefs."