Before you can say, ''Three cheers for upward mobility,'' somebody new seems to be explaining how the class system works in America. Ever since Thorstein Veblen wrote ''The Theory of the Leisure Class'' in 1899, sociologists have made a pretty fair upper-upper-middle-class living out of shuffling those hyphens while describing the status panic of Americans fumbling for the next treacherous rung on the rubber ladder of social preference.
And where would the American novel be without a full portrait gallery of nouveaux riches and lots of plots about young women from old families threatening to marry ''beneath them''?
Yet it's curious - every time the theme of class comes up, the latest author somehow assumes that he or she is a pioneer, exploring virgin territory. ''The subject has remained murky,'' Paul Fussell writes in his recent book ''Class,'' accepting one definition of class as ''America's forbidden thought.'' In an article on class in the latest issue of Success Magazine, Michael Korda argues, ''Nobody even agrees it exists,'' insisting that the whole tiptoe operation has always been ''conducted in shame-faced secrecy.''
Tell it to Jay Gatsby. Tell it to Henry James.
The fact is, if snobbery is the emotion proving the existence of class, Americans may well be the most class-conscious people of all time. Because nothing is ordained, we worry obsessively about what's ''in'' and what's ''out.'' In a search for The Authority that is never quite there - democracy be hanged! - we subscribe to publications like The New Yorker that are prestigious in order to discover from their ads, their articles, and even their short stories what else we may reliably take to be prestigious.
Which designer labels should one sport on one's clothes? What car ought one to drive to send up the correct signal? Where should one's children go to college? What is the ''must'' novel to read, the ''must'' film to see this season?
The very credit cards with which we pay for our status goods become status symbols, declaring exclusivity by their gold or platinum colors.
Even the games we play are assigned their hierarchy - tennis supposedly is more upper than golf, while squash is more upper-upper than both.
All these details make easy and obvious satire for both sociologists and novelists, leading to the easy and obvious conclusion, as Mr. Korda is only the latest to state: ''Old or new, money is what matters most.''
And so, when we're not pretending we're a classless society, we're inclined to turn discussion of class into a flippant, glittery parlor game about what's ''classy'' and what's not.
The history of class in America is a more serious subject than the usual jaunty approach suggests. For instance, the role of racism in determining class demands more scrutiny. Think of the far-reaching connotations of loaded labels like WASP, Boston Irish, or New York Jew.
We are still just beginning to realize how much of a class war Vietnam was, in terms of the Americans who fought it.
And how often do we remember that it was the ultimate in class distinction - slave and free - that led to the Civil War?
In this sense, the topic of class is still virgin territory, and those perennial pioneers announcing its discovery may be right. We need to think a good deal more about it - or a good deal less. In any case, the time has passed for trendy lists devoted to deciding whether it makes a chap seem more elite to own an Oriental rug or a Donegal tweed jacket.
A really classy person wouldn't care.