The simplest lessons are often the best, and one of the simplest lessons I've ever received is this: Film is an audio-visual medium. It seems so obvious that it shouldn't even be worth mentioning, but it bears repeating because it's important to remember that what you see and what you hear are important in film. The trick of narrative film is to make all the amalgamated elements of filmmaking--the photography, the sound recording, the editing, the acting--disappear into a story. The bigger trick of narrative film is to use those elements to tell the story for you, and that is something at which the creators of Lost were adept.
Audio-visually, the clues were there all along that this season was markedly different from the previous seasons, and it all began with the negative image of the Lost bumper at the close of last season after Juliette exploded the bomb. When we returned for this season, we had a new storyline, something that appeared to be a divergent continuum, and the first time we experienced what appeared to be an alternate reality, we were transitioned between the alternate reality and the regular Lost reality without the audio cue that we'd come to expect from flashes back and flashes forward. I remind you of these things to help you understand that our storytellers understand how to use the medium to give added depth to their narrative.
I believe Lost had two endings. One ending wraps up the narrative of the survivors' struggle for existence on the island, and the other ending is the ending to Lost, the series. For six seasons, we've watched as the survivors of Oceanic 815 struggled to build a community with each other in order to survive the horrors of the island as they battled polar bears, smoke monsters, Others, and even each other. The end of that story is that ultimately they did find that community and were able to enjoy it in death. The other ending is the actual conclusion to Lost. If you'll bear with me, I'd like to flash us forward to the closing moments of the show and a sequence of very important images.
In these six images we see Jack crumbled on the Earth, bleeding to death, joined by Walt's dog. From there we cut to the purgatory Church where all the survivors have reunited with their loves lost and friends found, where Jack and Kate finally get to be together. We cut back to the corporeal Jack, bleeding to death, happy as he sees Kate, Sawyer, and company fly away from the island. We return to the church, again, this time bringing closure to the Lost survivors' narrative. We now can be sure that the church is their heaven and that Kate, Sawyer, Lapidus, and Miles survived the island and made it back to the real world. From here we get a transition that we have not gotten before, and that is a fade to white and a fade back to Jack. This time, however, the shot has changed. We are not looking at Jack's body or head-- instead we get his eye. This is a callback to the pilot, where we saw Jack's eye open, which launched us into this grand adventure. Jack's eye closes. As I mentioned, the transition that precedes this shot is significant because the previous transitions have all been cuts, which is how the show's creators move us back and forth between the island and the alternate/purgatory stories. As we move to the eye, then, we are not returning to Jack's body on the island. Instead we are returning to Jack's real body on the island, the body that has survived for probably just moments, the wreckage of Oceanic 815. That eye that opened is now closing, and Jack, like everyone else, is dead. We go to the Lost bumper, and then an image of the flight's wreckage over the show's closing credits, which serves to underscore that everyone who crashed on that plane is dead.
Narratively, the show's creators have had their cake and eaten it, too. Yes, while everyone on the island is dead, none of them were dead in the story we were given. Yes, the island's survivors did end up in purgatory, but the purgatory wasn't the island, it was one of our characters' own making (which is fodder for an entirely separate post regarding the amalgam of religious ideas in Lost). For the purposes of our story, all of this did happen, and all of it was important, even if none of it actually happened and existed only in the desperate fantasy of a man about to die. This isn't "it was all a dream." It is "it was all a desperate delusion," and it doesn't matter that it was because we were given a meaty story with adequate closure and a fitting conclusion: Smoke monsters and Jacob don't exist, but our struggles, before we die, to ascertain the nature of this world, why evil exists, and why we haven't been better people do exist.
Edit 4/25 10:43 pm-- In the comments and on Twitter people have pointed out that the last image of the wreckage was added by the network. I would argue that it's the use of a a different transition to take us to Jack's closing eye that is meaningful. Take away that last shot, and you still have the show's creators taking us back to Jack's eye closing after the crash.