I may have said this all before...

I love the Back to the Future movies... I don't know why... probably leftover feelings from childhood... :) anyway... the plot of the second movie is profoundly confusing. One thing Doc made a big deal about in the first movie was how no one should know too much about their own future...but then he drags Marty(and Jennifer) off to the future and they see everything. Doc says they turn out fine, but that wasn't true either...Marty's back was broken in an accident... If perhaps Doc took him to the future to show him what his life would become, the mission to save his kids wouldn't exactly have shown him that if it had gone correctly.

...and the mission. To stop his kids from getting arrested...
I'l digress for a moment.
At a later point in the movie, Doc Brown busts out a chalkboard and explains (linear) timetravel to Marty, and while changing the past changes the future...Note the linear time travel part. He even draws a line.

Okay. Now if he goes and stops the kids from getting into trouble, he goes back in time to his home, and assumably then, knowing what his future life would be like... would change alot of things. That seems feasible, right? If I were to travel in time and see my kid was a big wuss like Marty Jr.... I'd probably raise him differently. Okay. So in that case, Marty Jr. would have never gotten bullied into trouble by Griff. Right? Making the future change. Now does this create an alternate reality, in which Marty and Doc DON'T come to the future because there is no need to help his kids? If it doesn't create an alternate reality...then what would happen when Doc and Marty came to the future that was already changed?

I'm giving myself a headache.
I hate time travel.