I finished watching the show a little over a month ago, after Lynch's death, since I liked all his movies that I had seen so far. I haven't rewatched it since, only Part 17 and Part 18. I confess that I liked S1, it was good, and I didn't like S2 very much, because that sequence of episodes really tired me out, which I think ended up affecting even my experience with Beyond Life and Death, which is still an incredible episode. On the other hand, I loved FWWM, and The Return is what brought Twin Peaks to such a high level for me that it's now my second favorite TV show, which is why I'd like to share my interpretation here. I didn't understand everything in the episode, like Eat at Judy's and the dead man in Carrie's house, but I think I got the central idea of the season and the ending after watching The Return and reading and listening to some other opinions. 

In Part 8, we see that the birth of evil comes from the atomic bomb, that is, from the works of humanity itself. Along with the birth of evil, good is also born, as the Fireman and Senorita Dido conceive Laura Palmer at the same time as Judy and her subordinates enter the human world. Thus, we can deduce that evil and good in Twin Peaks, having been realized at the same time, are two interdependent forces: one doesn't exist without the other. Proof of this can also be seen in the fact that Laura Palmer is canonized as an almost saintly figure in FWWM and in the OG show at the moment when she prefers to die rather than give herself up completely to Bob. In other words, Laura acts as the good because she was affected by evil and then rejected it, going through redemption, at the end of which she's rewarded with the angels' appearance. This clash between the benign and the evil is at the heart of Twin Peaks and an integral part of the show's identity. 

It's also important to talk a bit about Judy. She's an entity that's apparently absent from the universe, but in fact she's always been there. A very interesting interpretation that I heard in my research and with which I agree is that the phrase “the horse is the white of the eyes and the dark within” means that the horse is a representation of the act of looking away within the series – when the pupil is turned away, the whites of the eyes are highlighted. We can relate this to David Lynch's criticisms to the audience during the second season, when he was forced to reveal Laura Palmer's killer. At the time, Lynch said that people were desperate for answers and cared more about them than about art. These people that Lynch rightly criticized looked away from what mattered most in the series – Laura Palmer – and were much more interested in the killer, not the victim. Also, in the scene where the horse appears to Cooper in Part 2, he's looking away from Laura being pulled out of that place. The horse would be symbolic of these people, so much so that it appears more frequently to the character who was being most influenced – and then even possessed – by Judy: Sarah Palmer, the one who was at the trauma scene, but remained neutral to the situation and Laura's behavior, which was changing around her father. We can infer from this that Judy is the evil that manifests itself silently, in the most powerful way, the evil that distracts people from the good, from what matters. She acts indirectly, unlike Bob, who acts very directly.

In this sense, we can briefly analyze Part 17. This is the episode that promotes the maximum catharsis in the series and where many think The Return should end, but the solution adopted by Cooper wasn't the most appropriate, even though he said a very true phrase that shows the contradiction in illusory hope: “the past dictates the future”. Laura's death, understood by Cooper as evil, was actually the representation of good. It doesn't represent that evil has won, which is proven again by Laura's conclusion in FWWM. Regarding Cooper's phrase, if Laura hadn't died, it would've put an end to the city's anguish and given the conclusion that in the eyes of the majority would have been the ideal ending to the conflict, but these people have surely forgotten that, as the past dictates the future, in a much more distant past than this, the event that happened in Part 8 had already determined that Laura would be the one to fight evil and this defines her identity in the series. 

Now, about Part 18, we see that when Laura Palmer is apparently saved by Dale Cooper, she changes completely to try to suppress the trauma. She completely loses her identity and becomes Carrie Page. Laura Palmer is the girl who, even though she was tempted by evil, redeemed herself and didn't give in to it. Carrie didn't suffer from Bob's temptations; she didn't fight evil, she isn't Laura – yet. Laura has become, almost literally, the dreamer, who dreams of an end to her traumas and lives inside the dream. Along with Laura, the road to Twin Peaks – all the magic that was created in the pilot episode with Cooper entering the town – also completely loses its essence. Twin Peaks also loses all the hallucinatory atmosphere it had, everything becomes lifeless. 

When Cooper saved Laura Palmer, he looked away from her and valued his savior complex over the victim. In the episode in which he would get all his wishes by defeating Judy, he ends up falling for her game by looking away from Laura. He ends up leading Carrie Page to Alice Tremond, who lives in Mrs. Chalfont's house – whom I understood, in FWWM, to be evil entities from the Black Lodge, Judy's pawns, who encouraged the Lodge's influence over Laura. Twin Peaks became a town full of darkness because Laura no longer defeated evil in her death, which caused it to spread throughout the world. Cooper's impulsive attitudes ended up aligning with Judy's modus operandi and led Carrie Page to evil, in a place where they would fight each other, as the events of Part 8 had already predestined. The evil that calls out to Laura at the end of the series isn't Leland – the one who was possessed by Bob and physically abused and killed her –, but Sarah – the one possessed by Judy, who looked away from Bob's actions and allowed them to happen.

Carrie Page turns into Laura Palmer when evil confronts her, thus becoming good. She regains her identity when she's brought back into contact with evil. When Cooper saves Laura, he actually allows evil to win. Many critics of the episode say that his and Laura's trip to Twin Peaks was a waste of time and served no purpose. I think Lynch was counting on this criticism in a way. The magic of the trip and the city were all lost when Cooper saved Laura Palmer. Lynch wanted the viewer to feel what would happen to Twin Peaks if Laura Palmer was saved. The atmosphere of the series they loved so much was killed. 

Part 17 is an episode that shows that good cannot be destroyed, since Sarah couldn't destroy Laura's photo, only the glass and the frame. By contrast, Part 18 doesn't aim to show that Judy won and Laura lost, or vice versa, but rather that, just as good can't be destroyed, neither can evil. Since a very distant past in the atomic bomb, which dictated the future that now is the present, they're two interdependent, antagonistic and essential forces in the universe. When the clash between evil and good is prevented, Twin Peaks loses its identity completely and only "regains" it when the clash happens again. 

This is the reality and the end of the dream. Judy didn't win. Laura didn't win. Nobody won. They'll just be in constant and eternal conflict. That said, in my opinion, as well as that of many, Twin Peaks ends with Laura's message to Cooper, which kills his dream, now saying: “you can't save me”.

I'm sorry for any possible errors of cohesion and organization, but for me it's still confusing to put together the pieces of my thoughts on this episode. Is this interpretation valid?

My interpretation of Part 18