Due to the amorphous nature of Dear Esther, there are a number of theories available about the true plot of the game. Because the game gives players one of numerous combinations of dialogue, many open to interpretation, and some of which are believed to be outright hallucination caused by syphilis and/or blood loss, the player is invited to create a personal tale unlike those experienced by others. And even at points where the dialogue cannot diverge, interpretation will vary, possibly greatly.
The following are a few of the ideas and mysterious questions I've encountered in my short time researching Dear Esther. Some are countered by existing evidence in the dialogues, which I may not have seen yet. Others are baseless conjecture in forums. Many might be impossible to prove or disprove.
Possible Theories Edit
Is there proof that the Narrator and the player are the same person? What if they weren't? Is it possible the player is Esther, following her dead lover's footsteps as she reads his letters, watching with her own eyes as his guilty conscience drives her to suicide?
Given that we know much of the dialogue is given incorrectly by the Narrator and that he knows much is given incorrectly to him, is there a chance the island is not even real at all? Could the events of Dear Esther be the delusion of a near-death experience? A drug addled haze of half-remembered traumatic events in short term memory combined with a massive dose of morphine? A solitary limbo, a purgatory of one, in which a guilty party is doomed to repeat these events, and "come back," infinitely? This certainly would coincide with the end of the game.
If the island and events really are taking place as we see them, how much should be taken literally? The trail of visual evidence includes photos, ghosts, painted diagrams, wreckage, and much more. Can any of it be taken at face value? Who painted the words and diagrams throughout the island, especially in the most inaccessible locations? If there are only five identifiable people mentioned, why are there more than five ghosts? If the island has been all but abandoned, even by shepherds, since 1700, who erected the aerial? Paul has been mentioned being charged with maintaining the aerial, or was it the narrator?
The narrator is clearly experiencing heavy dissasociation nontheless, which is indicated when he at some point mentions how Paul climbed up the aerial, but didn't know how to climb; resulting in a broken leg. Later on, he explains how he (the narrator) broke his leg on the way up. It is possible the delusions he suffers is caused by heavy use of painkillers due to severe pain in regards to blood loss and fractures.
The narrator may also very well be alive, including Esther. If you attempt to swim or otherwise stray too far from your intended path, the screen will fade to black, your heartbeat will increase and you will hear "come back..". Not only that, but you will see faint visions of the submerged highway and Esther. The increased heartbeat may be as a result of brain activity in a coma, almost fading away. The voice you're hearing could very well be Paul or her husband. We have both seen it in movies, people talking to people in a coma about everyday things. This may be explained by the narrator saying 'he met Paul yesterday' early in the game.
So it is very possible that Esther is alive, but struggling for her survival. The letters can be explained by some past events if they ever dissolved their marriage or went through a long-distance relationship at one point. It could be that Esther in her coma, is thinking herself that she is completely dead, or even that her husband is. That may be the reason why the player loses control and jumps from the aerial and turns into a Seagul, symbolizing that she indeed died, but that she/the narrator has a relief from the constant guilt and mental torment; feeling free.
The ghosts are possibly mental reflections of sorrow or loss. This theory is contributed by the fact that if you noclip to the ghosts, you will see either a decomposed body, or a hooded, faceless figure. Or even Esther. They maybe ghosts of the islands past the hooded figure could possibly be The Hermit and other figures could be Donnelly and Jakobson. They might also be projections of heavy morphine doses, fear and delusions.
The ending can be interpreted in several ways, working off the basis that the protagonist is in a coma, their suicide at the end of the game could be the moment of flat line. The protagonist could have given up after losing (or believing that he has lost) Esther and lost his will to live, this is hinted several times, namely when the Narrator states that his infection is "more than the flesh."
The protagonist could also be waking from their coma and after they throw themselves off the aerial, wake up in their hospital bed starting a new life. The protagonist morphing into a bird could represent some form of reincarnation allowing the protagonist to begin again. If the protagonist is Esther/Narrator and the other person has died then turning into a bird could possibly be the representation of them beginning a new life.
The bird itself could be a representation of the protagonist shedding their troubles and being granted freedom like a bird has the freedom to fly wherever they choose. From a spiritual perspective it could also be a transformation into a form of celestial being equivalent to an angel, them leaving the island moving on to a life after death. This could possibly imply that the island is a form of purgatory, perhaps a personal purgatory for the Narrator or Esther and the protagonist has to overcome their troubles and grief of their loss.