I think JMS once said that you never heard the word "arc" until he started using it. The concept is really fairly new to television, I think.
If he did say that, he's got a short memory. The Ken Wahl series
Wiseguy popularlized the notion of "arcs" - using that word - beginning in 1987, six years before
The Gathering first aired.
Wiseguy's arcs were the hero's undercover assignments, which ran for different lengths of time, and each of which had a pre-planned beginning, middle and end.
Basically there are three kinds of TV shows:
1) Episodic or "stand alone". However, even these have some degree of continuity from season to season.
Friends is episodic, but events and relationships change over time on the series, and an effort is made to keep things straight. Everyone doesn't forget what happened in each episode by the next week. (Which is typical in "pure" episodic shows.)
M*A*S*H and
Magnum, P.I. are two other shows that used recurring characters and a degee of continuity while primarily being stand-alone shows. The various
Law & Orders are more episodic, but even they contain elements of continuity. Most shows these days do, and the trend started years before
B5.
2) "Continuity" shows. These are shows that carry plotlines and development from episode to episode, but not necessarily according to any kind of master plan.
Hill Street Blues was a continuity show. It ran "arcs" that were preplanned across five or six episodes, but didn't have a beginning, middle and end in mind
for the series. Steven Bocho's other series, including
L.A. Law and
NYPD: Blue take a similar approach. Perhaps the classic "making it up as we go along" non-arc continuity show is
The X-Files, which gradually became choked by its own mythology precisely because creator Chris Carter
didn't have an over-all plan in mind. Again, "continuity" shows are increasingly common on TV. The 60s era stand alone, where nobody seemed to remember this week what had happened last week (
ST: TOS, virtually any sitcom from the period) is largely a thing of the past. Most shows pay at least lip-service to continuity. The model for all such "continuity shows" is the soap opera, which imported its story-telling style from radio. While most soaps have a master plan for each year, few lock themselves in beyond that, and all will improvise to deal with cast problems, incorporate current events into the plotline, etc.
3) Genuine arc shows. These are rare, because one of the thing a real arc requires is a fixed end point. Since TV shows tend to lurch from season to season it is hard to write a well-shaped arc because nobody knows how long it is going to be.
Blake's 7 was going to be a limited series from the beginning (something much easier to do on British than on American Television) so this wasn't a problem. JMS's refusal to do a sixth season and his insistance from the beginning that the show was a five year story was a recognition of this. Of course, some shows have a
premise the looks forward to some definite ending (Richard Kimbal catching the one-armed man in
The Fugitive, getting rescued and returning home again on both
Gilligan's Island and
ST: Voyager .) But the episodes that fall in between the pilot and the finale on these shows rarely make up an arc. True arc shows are indeed few and far between, because they are the hardest of all to do. However, the success of "continuity" shows like
Hill Street in its day, and
L.A. Law or
NYPD: Blue in more recent years suggest that there is an appetite for at least that much of a continuing story, which means both network executives and audiences may be a little smarter than some have suggested in this thread.
Regards,
Joe