Back To The Future 3 - Know Your Own Future?
Marty and Doc discover the outcome of Docs "new life" in the Wild West, as they see his grave in 1955. Then why does Marty have to go back to 1885 to warn Doc if he already knows his own death date and time. Correct me if I'm wrong, but the Doc of 1955 is the same Doc of 1985 who accidentally goes back to 1885. Therefore he should theoretically stay away from Mad Dog upon his arrival to 1885, ending the need for Marty's adventure. And don't say he still needs Marty to come back so he himself can travel back because he has no problem building a "Time Machine" from a steam train as he proves when he and Clara both show up in it at the end of the film.
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