I discussed this a bit in comments elsewhere, and I just wanted to continue thinking about it out loud (so to speak). There are two ways to look at a television series. One is as a long, continuous story about a family, or a workplace, or some other setting. In this view, a television series with continuing characters is analogous to the 19th-century novels that were published in serialized form. As with those novels, sometimes the different parts can have tight continuity and tell a coherent story that develops from beginning to end (like the late novels of Dickens), and sometimes the structure can be episodic, with the different parts not always having a whole lot to do with one another (like Dickens’ first novel, The Pickwick Papers), but the operative point is that it’s all one story that keeps moving forward.
The other view is that a television series is a series of little movies that use the same characters as vehicles for different situations, problems or issues. Looked at in this way, a television series is not like a single novel, but more like a whole bunch of individual novels or stories. The origin of television, from this point of view, is the “series” of individual B-westerns or mystery novels or magazine stories, which might bring back the same character under the same name, but where it was understood that the character would always be the same when each new story began. Sherlock Holmes, Jeeves, Roy Rogers: these characters cannot grow, change, or learn from their experiences — at least not from adventure to adventure. (Characters in these kinds of stories might learn something within an adventure, but they will un-learn it by the next adventure.) Continuity may exist, but only in the sense that they remember things that have happened in previous adventures, not in the sense that their adventures have any kind of forward motion. There is no forward motion, because each instalment brings us back where we were before.
The odd thing about series television is that its format has parallels with both “highbrow” and “lowbrow” forms, with the “high” form of the major novel and the “low” form of popular series fiction. Every maker of an ambitious TV series will point out, correctly, that TV is to our era what the novel was to Dickens’. But it’s also true that filmed TV grew out of the B-movie; when TV killed off the market for 70-minute programmers, the same people went into television and made the same exact kinds of productions, except now they were 50 minutes long instead of 70.
Every mass medium has its high and low aspects, of course. What’s a little different about TV, and what can make it hard to evaluate, is that the form can actually defeat some of the assumptions about what makes good storytelling. In a feature film or a novel, whether it’s ambitious or trashy, there is always an assumption that your lead character should learn something or prove something or somehow be in a different place at the end of the movie. Even if it’s just John McClane reconciling with his wife. And if the characters are “flat” characters who can’t change, then at least something can change around them: they’ll win a major victory or lose a truly devastating loss. But in much of television, there is no time to get your character to a different place, and no point to it; he’ll be in the same place next week, and the audience wants assurance that he’ll be in that place next week. (This can even be true in serialized, “novelistic” television, because the form of an individual TV episode is so heavily influenced by television’s origin in the B-movie series. Characters may wind up in a different place on such shows, but it’s a big surprising moment when they do. It’s not to be taken lightly.) Characters can never really change, but they also can’t really win, or improve their lives, or overcome obstacles, or anything else that makes for a satisfying climax to a story. Some shows, like Seinfeld, even make a big existential joke out of the fact that the characters are doomed, by TV convention, to never win, never move on, and never improve.
With TV, then, particularly non-serialized TV, a lot of the usual ways of judging a work of art don’t completely apply. We cannot judge a TV episode by whether the character is in a different place or learned something (part of the reason “lessons” on TV are often so fake is that we know they’re meaningless; if the characters really learned anything, half the story ideas would be gone). The only obstacles the protagonist can overcome are external ones, like catching the murderer. And though TV can and should aspire to the status of a great novel, the way TV shows are made — episode by episode, season by season — makes them inherently incoherent; the best of them are incoherent in a lovable way, like The Pickwick Papers. Television is a medium that can theoretically develop characters at great length and with great complexity, but practically finds itself rooted in forms and styles where characters cannot really be developed at all. A great television series figures out how to do the impossible, which is to create a sense of an unfolding world while dealing with the need to keep that world essentially static.