I’m taking a class this semester called Philosophy through Film, and one of the assignments is to write a journal entry for each movie we watch. My previous entries are on Being John Malkovich, Eternal Sunshine of the Spotless Mind, Memento, Pulp Fiction, One Flew Over the Cuckoo’s Nest, Groundhog Day, Crimes and Misdemeanors, and the Matrix. I've also written an extracurricular post on The Hunger Games. We watched the Director's Cut edition of Donnie Darko in class, so I will be discussing the content in that cut. If you've only seen the theatrical release cut, I may be talking about stuff that makes even less sense than the movie did.
Purpose in Donnie Darko
I'll start by offering my usual dismissal of metaphysical claims in Donnie Darko: all films have the same metaphysics, everything in the universe is governed by the will of the cast and crew. But apart from that, the film does have interesting things to say about humans' relationship to metaphysics.
Donnie is a teenager, tormented either by a huge burden placed on him by a quirk of spacetime, or by his own psychological problems. He's faced with deep angst in his pursuit of a grounding principle -- some basic truth on which he can build his decisionmaking.
While pursuing this basic truth, he generally puts off decisionmaking until he's nudged towards an immediate course of action by the forces around him. His indecision leaves him easily manipulated by Frank, who offers him a few ideas on how to behave, and by the visible manifestations of fate that suggest paths for him when the plot has no other reason to get him where it needs him. (I think this is justified, if he is actually living in a bubble universe that's trying to reconcile itself to the continuity of reality, so I'm not criticizing the plot when I point out that the fate-paths bring him places he has no other reason to go.)
Ultimately he finds his purpose, his grounding principle, in Gretchen -- his desire to give her a life, in exchange for his own. In this sense, I think the film hits the nail on the head -- searching abstracts about free will and determinism, looking for God or comfort in the face of death, seem like promising paths, but just become more discouraging the deeper you look. For a solid first principle, relationships with other people work much better.