Doc: "I've made a decision."
Doc: "I'm not going with you tomorrow. I'm staying here."
Marty: "What are you talking about, Doc?"
Doc: "There's no paint in denying it. I'm in love with Clara."
Marty: "Oh, man, Doc, we don't belong here, neither one of us. You know, it could still be you that gets shot tomorrow. This tombstone could still be in your future."
Doc: "Marty, the futire isn't written. It can be changed. You know that. Anyone can make there future whatever they want it to be. I can't let this one little photograph determine my entire destiny. I have to lead my life according to what I believe is right, in my heart."
Marty: "Doc, you're a scientist. So you tell me, what's the right thing to do, up here?"
Doc: "You're right, Marty."