To the extent that TV has always been an advertisement for something, it was often an advertisement for the middle class: a job, a family, a home, products to put in it. But early sitcoms engaged with matters of aspiration and failure, and they were tied to work. If employment didn’t define a character from episode to episode, it sustained him (and it was usually a him). Some, like Jackie Gleason’s Brooklyn bus driver, Ralph Kramden, the human caldron of “The Honeymooners” (1955-56), had jobs. Some, like Dick Van Dyke’s Rob Petrie, the klutzy TV writer on “The Dick Van Dyke Show” (1961-66), had careers. Work, or the lack of it, slotted you into a clear socioeconomic class. Kramden’s dissatisfaction — he devoted a lot of time to hatching get-rich-quick schemes — became the tacit sadness of the “The Honeymooners.” It was the first rueful sitcom. Petrie had a suburban-New York living room that Kramden would have killed for.

By the 1960s, prime-time television was barely two decades old, and it was already a little nostalgic and class-neutral, broadcasting shows safely ensconced in either the suburbs or the distant past. But the decade’s relentless turmoil (civil rights, Vietnam, political assassinations, Watergate, feminism) demanded discourse. On TV, that conversation happened in the living rooms of the working class, middle class and working poor, on “All in the Family,” “Maude” and “Good Times,” each a creation of Norman Lear, each a demonstrable emblem of its characters’ social station. Archie Bunker (“All in the Family”) was a white foreman in Queens; Florida Evans (“Good Times”) was a sporadically unemployed black housekeeper in Chicago’s Near North Side projects. Bunker's armchair racism, sexism and all the rest wouldn’t seem to have anything to do with Evans's prideful despair. But the two shows dramatized their opposing dissatisfaction. Class was the perch from which to see who you were and were not, and from which members of the television audience could see who they were, too.

The discontent on those shows ran like a fuse through the 1970s into the late 1980s. The end of the Reagan era and start of the first Bush administration coincided with the arrival of “Married ... with Children” and “Roseanne,” a pair of long-running sitcoms about the white lower-middle class and working poor — the Bundys and Conners, respectively. The first was more bitterly toxic (my mother got a whiff of its vulgarity and forbade it) than the second. But each show descended from Lear’s righteous class consciousness. And each felt like a rebuke of the vertiginous affluence and physical beauty of soaps like “Dallas” and “Dynasty” and a rejoinder to the upper-middle-class comfort of “The Cosby Show.”