Coming into the sixth and final season, "Lost" was always going to be up against the high expectations of both its most devoted fans and its most fervent critics. For the fans, this was the culmination of six seasons worth of character and plot building, and the payoff that was promised when Damon Lindelof and Cartlon Cuse famously negotiated a firm end date for the series. For the critics, it was the opportunity to point out all the things that had been left dangling over the years, especially once all was said and done.
Much has been made of the notion that the entire series was "planned out" from the beginning. Fans and critics alike tend to overstate what this means. Even the most detailed plan for a television series rarely survives the pilot stage. Examples like "Babylon 5" are rare, and that level of consistency to original outline was due to one person's dedication to story (the creator/writer wrote nearly every episode for the final three seasons). Even so, several changes were required due to casting and budgetary constraints.
"Lost" was no different, and given the scope, there had to be a lot of leeway. I firmly believe that Lindelof and Cuse had a basic outline and plan for the scope and direction of the series, and that it was tightened up dramatically once the deal was made to set an end date. It's also clear to me that they would take that basic roadmap and adjust it for each new season, to fit the demands of the narrative, the available cast (especially guest stars), and the budget considerations. And finally, the episodes themselves had to be written with maximum flexibility in mind.
This may sound like a fan making excuses, but let's face it: this is not a case of two co-writers putting out a series of six novels, where they can control every aspect of the story and ensure that all the pieces fit together perfectly. This is a television series in which the integrity of the story as a whole, over the course of six seasons, is dependent on dozens of moving parts. As with the aforementioned "Babylon 5", if even 80% of the plot and character elements pay off reasonably well, then it's a massive victory for something of this scope and vision.
To their credit, the producers did try to shape expectations by reminding the audience that the show began as a character-centric tale. The first season was almost entirely devoted to character. The plot and mythology elements, while definitely a major part of the show's DNA, were almost always tied to some facet of a character and their personal journey towards (or away) from redemption. After all, nearly every episode had a character flashback, flash-forward, or flash-sideways that illuminated the psychology of the character at the center of an episode.
As often as my reviews, commentary, and speculation focused on elements of the mythology over the course of the series, the big questions were always the motivations of the characters. The mysteries of the island were only important insofar as they might factor into those motivations. The worst episodes were the ones that failed to sell a character's choices. After all, what makes the mythological aspects of the show work are the universal themes of choice, consequence, and redemption.
So going into the final season, I was more than willing to accept that some of the mysteries were going to remain untouched. It had long since been established that the story was being told from the point of view of certain characters, and they had a galling tendency to only ask questions that were pertinent to their limited perspective. In other words, the characters themselves didn't have a lot of the information necessary to ask the bigger questions. And unlike the audience, those characters weren't exactly in a low-stress situation with plenty of time to puzzle over the nature of the island and its history.
Enjoyment of the sixth season seems to have been based upon reaction to two things: the flash-sideways narrative device, and the shift towards the mystical.
A lot of fans seemed to hate the flash-sideways segments, but I enjoyed them, even when I was on the "alternate timeline" bandwagon and furiously trying to reconcile the growing list of inconsistencies. In retrospect, the "alternate timeline" explanation simply wouldn't have worked to explain what was presented, so the metaphysical "purgatory" explanation actually makes the best fit.
That said, it was a stunning revelation, and I can see how some fans would be taken aback by it. Yet the very nature of Jacob and his unnamed brother were rooted in the mystical, especially once the blatantly mythological tale of "Across the Sea" explained their origins. "Ab Aeterno" introduced the idea that the island was a metaphorical cork in the gateway to Hell. The entire season was laced with metaphysical concepts and metaphors, so the "purgatory" reveal was stunning yet perfectly in keeping with that theme.
As already stated, in retrospect, the flash-sideways ("Lost X") material now makes a lot more sense as something of an epilogue to the main story on the island. In fact, if one only watches the "Lost X" material on its own, it makes contextual sense with how it was explained. Several points along the course of the season point to the "purgatory" explanation, including the very first moments in "LA X". While some still speculate that the writers developed the "purgatory" plot twist very late, due to sloppy continuity mistakes earlier in the season, the evidence is to the contrary. If anything, the "Lost X" material works better and better on repeated viewings.
While much of the discussion has been devoted to "Lost X", the main storyline ("Lost Prime") was coming to a rousing conclusion. Ironically, if there was one weak aspect to this season, it was not the flash-sideways; it was how the writers tried to wrap up certain elements of the mythology in ways that just didn't seem to work. In some cases, it made an otherwise strong episode decidedly more average.
Lindelof and Cuse often spoke out against the notion of giving too detailed an explanation for the mysteries of the island. After all, in typical JJ Abrams form, it was more the idea of the mysteries and what they represented that meant more to the story. If one looks at nearly every genre offering that Abrams and his production/writing cadre has released, there is a central McGuffin.
On "Alias", it was the Rambaldi artifacts and prophecies. On "Fringe", it is the Pattern. In "Star Trek", it was Red Matter. In "Cloverfield", it was the monster. The list goes on and on, but the concept is the same. Abrams' success is taking a general sci-fi or fantasy concept and building a character-driven story around it. In many respects, this is very similar to what Joss Whedon does. (In fact, there are many who point out just how fast and loose the mythology elements tend to be on Whedon-driven series as well.)
In the case of "Lost", it was the island. The island was never meant to be explained in absolute terms. Instead, it was meant to represent the threatening unknown. It was a metaphor and catalyst all in one: a sort of Shangri-La where these lost souls could find themselves (or die trying). The problem with explaining the metaphor is that it stops being a metaphor. It suddenly needs to have an origin and a purpose.
When the writers did try to pay off long-standing mysteries with detail, it often didn't work as well. For example, the explanation for the "whispers" was altogether too pat and didn't fit within the context of how the "whispers" had been portrayed. The explanation for the nature of the electromagnetic/temporal anomaly at the heart of the island was about as close to cheesy as the series ever came. The explanation for the "frozen donkey wheel", while thematically meaningful, never quite rang true.
That said, the island was always portrayed as a character in and of itself, and metaphorically, that worked tremendously well in this season. Some might quibble over the vague explanations involving the Source and water, but it was a clear analogy to a human being's heart and circulatory system. The Source was the heart of the island, and the water flowed through it like the lifeblood through our veins. (Which almost demands that one go back and look at the role of water over the course of the series.)
Does it matter that the series finale never explained how this metaphysical Source was controlled or regulated by some ancient device, if it was tied to the life-force of every living thing on Earth? Not really. It's enough to know that people have always tried to possess its power, and that someone harnessed it in a way that made it all too easy to extinguish. "Across the Sea" made this conceptually clear by establishing that Jacob was simply the latest in a long line of Keepers of the Source.
To take this to another level, what this season revealed about the island is that it was something of a spiritual metaphor, even beyond its supposed nature as the "cork in the gateway to Hell". Granting that within the context of "Lost", there is a much higher power, which created the Source (and therefore the various states of being that play into "Lost X" and the series finale), it is so far beyond the full understanding of the characters and "normal" human experience that it is ultimately only evidence in its effects.
Similarly, we knew the universe exists. If we extend the spiritual metaphor in strictly non-denominational terms, "God" could be defined as the conscious totality of the universe. And while we, as human beings, attempt to understand the workings of the universe rationally through the application of science, there are simply many aspects that are still elusive. Quantum theory is supported by many experiments and practical applications, for instance, but it is still mostly understood in terms of its effects.
Looking back on the series as a whole, there are examples of humanity attempting to understand the mystery of the island. The Dharma Initiative brought the best and brightest to the island (by their own measure, at any rate), and they only scratched the surface. Daniel Faraday delved even further into the mysteries, and ultimately came to the wrong conclusions based on his limited understanding. Beyond science, there were the pseudo-religious interpretations of Richard, Locke, and the Others.
The message, it seems, is that the struggles of the characters on the island, seemingly alive in its own way and beyond definitive understanding, are a reflection of humanity's struggles in the real world. Which, of course, is the essential theme of the series as a whole. The struggles of the survivors of Oceanic 815 were our own struggles, and science and faith were insufficient to capture the meaning of it all.
It was the sixth and final season of "Lost" that brought the entire story full circle and opened the door to this level of conceptual understanding. Needless to say, there are many fans and even more critics who found that set of "answers" to be unfulfilling and perhaps even intellectually bankrupt. Yet these are massive philosophical questions at the heart of human experience.
It is a false assumption to say that a show with science fiction and fantasy elements cannot ultimately rest on those philosophical underpinnings. As always, I must point to "Babylon 5". While it's possible to view the series as strictly science fiction in origin, the series finale ("Sleeping in Light") reinforced that it was a story about overarching questions about ourselves and our place in the world: who we are, what we want, why we are here, and where we are going. All questions that were at the philosophical center of "Lost" as well.
The sixth season of "Lost" earned a Critical Myth rating of 8.7. This is easily the highest rating achieved by any season of a series I've reviewed, and a dramatic step above the already excellent fifth season (8.3). As a whole, "Lost" earned a Critical Myth series average of 8.0, which itself is the highest overall rating for any series that lasted more than a single season. ("Firefly" earned a series rating of 8.5, but as it only ran a total of 14 episodes, this is an unfair comparison.) This is an achievement that has been, in my opinion, capably earned.