That Butler is playing Clio, the ancient Greek Muse of history; that the mortal (Jackson) with whom said Muse falls in love is a 1970s L.A. sidewalk artist who dreams of opening a roller disco; and that the villainesses are two jealous sister Muses who rat on her to Zeusnone of this need worry you, even in its idiocy and incoherence. Posters on theater chat sites may proclaim it as the end of the world and the death of the American musical, but Western culture has always cherished a streak of theatrical inanity like this, running wider or narrower according to the times. We live in lousy times, that's all. The week I saw Xanadu, I'd been reading a collection of late 18th-century afterpieces, the silly diversions theaters put on following Hamlet or The School for Scandal in the pre-television era, when people expected an evening at the playhouse to be a long one. A few of the writers had some wit, but mostly the scripts were far stupider than Xanadu, and not nearly as amusing. Of course, you got Hamlet for your money too, but the evils of capitalist distribution are not a drama critic's concern, though it's worth noting that Marxism, like other movements toward violent revolution, arose just when the theater was at its most trivial, concentrating its efforts almost wholly on diversion. More on this point, and on Robert Wilson's Comédie-Française staging of La Fontaine's Fables, next week.