Los Angeles ? “Lost,” the most complicated series in the history of television, will come to its end Sunday and without having seen a second of its 2 1/2-hour conclusion, I prophesy that it will leave many viewers unsatisfied, either because it will say too much or not enough, or because it will be too explicit or too vague, or too prosaic or too mystical, or too final or too inconclusive.

From left, Emilie de Ravin, Jorge Garcia, Evangeline Lilly and Josh Holloway are shown in a scene from the sixth and final season of “Lost.” The series finale airs tonight on ABC.

Endings are always tricky. Television has done without them for most of its life; for years series were canceled and disappeared without ceremony, but nowadays, with a serial strain running through even highly episodic shows, it is more usual to aim for some sort of closure. (Just as it’s become more common, in life, to think we need it.) Nevertheless, there is something in the very structure of American network television that is inimical to finality: New shows are launched hopefully to run forever; they are made for cliffhangers, not conclusions.

When they do come, the conclusions tend to be straightforward: a villain is defeated, a patient cured, a job finished, a romance finally begins. But “Lost” is something else: The mystery at its heart is “What is the nature of this mystery?” and the job of the last couple of seasons has been to explain (some of) what’s come before, even as the show has charged continually ahead into new territory and drawn a curtain over old business — or have you forgotten how your world once turned on knowing the ins and outs of the Dharma Initiative? This is explication not just in the mechanical sense, as when the detective reveals how the man in the locked room was murdered; in some more thoroughgoing way, it is meant to tell just what you have been watching the last six years.

The people behind the series — it was created by J.J. Abrams, Damon Lindelof and Jeffrey Lieber, and managed subsequently by Lindelof and Carlton Cuse — may well have known, if not from Day One, then from Day Two or Three, that their mysterious island would be the staging ground for some ancient tussle between good and evil; reason and faith; light and dark; handsome, young leading man and aging, craggy character actor. (Which is not to say that some other, unexpected twist won’t wrench the whole thing 180 degrees come tonight.)

But the particulars have clearly taken shape over time, in response to the felicities of casting — Michael Emerson coming in for what was originally a three-episode arc as Ben Linus was an admittedly lucky stroke — and feedback from the fans: The life of the show fortuitously coincided with the rise of the blogosphere, professional and amateur; with its puzzles and anagrams, Easter eggs and red herrings, it is made to be picked apart and obsessed over.

If there have been too many characters, too many random images and scattered loose ends, to expect any unified theory of “Lost,” well, I’m not particularly anxious to get one. Answers kill mysteries, and in a mystical mystery like “Lost,” the answers will never be as good as the slippery things you can almost imagine. A polar bear on a tropical isle is a vibrant image, but it becomes immediately less compelling when you learn it was just part of some experiment.

It has been common to describe the series as the story of a man of science versus a man of faith, but, really, it was all about the faith here. (The man of science, Jack, has come around to that opinion and looks to become the island’s new Christ figure — or not — while deceased man of faith Locke is currently inhabited by a quite rational monster made of smoke.)

Science on “Lost” is not real science; it is magic with a button attached, or a lever, or a wheel. The local physics are whatever fits the situation: “If the light goes out here, it goes out everywhere,” guest star Allison Janney said of the island’s glowing “heart” a couple of weeks back, whose light Jack is now slated to protect. (“You know that how?” I wanted to ask.) Write some names on a cave wall, or repeat a series of numbers everywhere you can think to put them (including next to the names), and they glow with meaning. Explain them, and they glow paradoxically dim.

If we are to trust what we have seen recently — and I wouldn’t, not completely, with 2 1/2 hours still to go — we are facing a fairly familiar endgame in which a hero will sacrifice himself to keep a genie bottled up. Local good-god Jacob’s speech last week to the surviving four castaways, telling them why they were there — as “candidates” to replace him, chosen because they were “flawed” and in need of what the island had to give — sounded pretty flat and unconvincing to me.

Somehow I am not worried; the particulars of the story have never been what “Lost” is about for me. There is something always at work beneath the surface in this show, a kind of structural poetry that embodies its themes of coincidence and fate through parallel actions and mirror images, visual and verbal echoes across space and time and, lately, worlds. (I speak of the flash-sideways universe in which even the dead castaways are alive, and thriving, and which may allow the characters to have their happy endings.) These devices are the meter and rhyme of “Lost,” and — with the rhythms of the actors and the colors of the island — they’ve kept the show kind of beautiful, even when it hasn’t made much sense or has wandered into unprofitable cul de sacs.

As to why those people are on that island, I believe I know the real answer: They are there for you.