This title is no Quantum of Solace or Far From The Madding Crowd. You don't have to crack open a dictionary or thesaurus to get to the root of this one. The movie's called Back to the Future because Marty's trying to get… back to the future.
But it is a little strange that this is a movie about a time machine, with the word "future" in its title, and it's mainly about the past. Were Spielberg and Zemeckis trying to say something about how time is circular, or that, because we end up becoming our parents, there's not much of a difference between our past and our future?
Eh…probably not. But that doesn't mean that you can't unpack Back to the Future like a moving truck full of boxes. Just because this movie is a light comedy that contains shenanigans like running into manure trucks doesn't mean that this movie—like any work of literature, from SpongeBob to Sound and the Fury—doesn't contain seriously deep philosophical implications.