How we cite our quotes: All quotations are from Back to the Future.
Quote #4
Doc: It's taken me almost thirty years and my entire family fortune to realize the vision of that day.
Key bit of information here. "My entire family fortune." So Doc used to be rich… which explains the nice, big house and access to expensive lab equipment. But when we meet him: no family, and no fortune. He sacrificed everything to achieve his vision. Now that's some ambition right there.
Quote #5
Doc: That's right, twenty-five years into the future. I've always dreamed of seeing the future, looking beyond my years, seeing the progress of mankind. I'll also be able to see who wins the next twenty-five World Series.
Another piece of valuable insight here is revealed by the words "seeing the progress of mankind." That's the main reason Doc wants to go into the future. Not to look up old friends, or see if the Eiffel Tower is still standing. His life revolves around science—it's his love and his passion—and the only thing in the world he wants is to see progress.
Quote #6
Goldie: No sir, I'm gonna make something out of myself. I'm going to night school and one day I'm gonna be somebody.
One of the most ambitious young characters in the movie doesn't get much screen time. But we know Goldie follows through on his dream, because in 1985 he's up for re-election as mayor. At least someone got their act together.