Fable: "a short tale to teach a moral." In this case we clearly have echoes of Cervantes: a Don Quixote idealist (McPhee) paired with a Sancho Panza realist (Fassbender) in search of Dulcinea (Pistorius), who may not exist -- at least, as they imagine her. Fables don't require complexity of character, and these are pretty much one dimensional.
Two things stood out for me: (1) Fassbender's performance: so at ease, so natural; it made me realize how he's been wasted. We should see him far more often.
And (2) New Zealand added a wonderful, dream-like otherness.
Who is telling this story? The voice-over purports to be the Realist/Fassbender. But the camera, the scenery, and the music express everything from the POV of the idealist/McPhee. What's going on?
I think that Fassbender's character, as he tells the tale, tries to put himself into the character of the kid, and, as realists will do, he exaggerates the kid's simplicity and naivety. Maybe that's why so much of the dialogue comes off as Becketlike hokum.
Unfortunately, the effect is to lose the audience. The young man was played so dumb I lost any sympathy for him. But maybe that was the point. In one scene, he is shaved by Silas (Fassbender). For a few moments he looks like a more mature person. He is about to become a man., But half way through they are interrupted and he doesn't make it. Presumably sentimental innocence can never grow up.
The narrative structure explained some other oddities, particularly in the case of the Girl/Pistorius. In the young man's remembrance she's presented as a romantic idol. But there's a hint of a different reality when she declares to him that he is "like a little brother," On the strength of this questionable sentiment, though, he journeys all the way to the West. But how does the narrator know this? Is he reconstructing from the kid's narrative and from what the girl may have told him later? Incidentally, that's probably why the background story set in Scotland is so sketchy.
When we see her through the Silas' eyes, though, she's the opposite of conventionally "domestic": she can shoot a rifle but she can't figure out how keep butter from melting:.
Is Silas a reliable narrator? I think he really killed the kid, and probably the other suitor as well.
The Moral: the Realist, not the idealist, gets the Girl.