From the IMDb page listing goofs for Back to the Future Part III comes this marvelous entry:
bq. *Incorrectly regarded as goofs:* The complex logic, and conflicting theories, of time travel have resulted in a great many potential plot holes, especially when the movie is viewed in the context of the whole trilogy. But time travel movies are like that.
I find it highly amusing (and a bit disturbing) that people on the IMDb message boards are still to this day debating the logical inconsistancies of the Back to the Future time travel storylines. I could not possibly think of going into that movie as a “serious” treatment of time travel. I mean, they have hoverboards and ads for _Jaws 17_ and Michael J. Fox plays his own daughter. Not hallmarks of a “serious” time travel movie.
Well the thing that always bothered me, is that Doc Brown goes through this whole speech about not thinking “4D” enough, and that they couldn’t go forward in time because they’d be going forward to the new timeline. But somehow biff brings the time travel machine back to the future after giving himself his book? I think I would have been fine had they not attempted to explain the rules earlier.
wait…. are you telling me that the doc is wrong?!