I tried to debate this with my mom but she refuses to get what I'm trying to say.
Back to the Future SPOILERS AHEAD
We were discussing the friendship of Marty and Doc. I mentioned something the creators said about how they met which my mom disagreed with.
My moms' argument is the stable time loop theory. That Doc always knew the two of them were destined to meet.
My argument is that Marty changed the past creating the paradox and their meeting wasn't predestination in the original timeline. We know this because Martys' actions change his familys' entire life which wasn't possible until he time traveled. After he comes back yes there's a stable time loop but not in their first meeting.
Doc dies in the original timeline and is only able to save himself because Marty left him a note creating an alternate "corrected" timeline. Sort of like what happened in the second movie with Biff in control only on a smaller scale and with it becoming the lasting reality. Likewise Claria was originally supposed to die until Doc saved her.
Original timeline-The McFly family isn't doing so well with a drinking problem, a strained marriage, dead end jobs, etc. Doc dies. Claria died in the past.
"Corrected" timeline-Marty gets his dad to stand up for himself and become more confident. His parents are happy, his dad pursued his passion in writing and is successful. Biff is the meek one and Marty's siblings are happier. Doc survives thanks to Marty leaving him a note. Much later on Marty can't overcome his problem with backing down when someone questions his guts leading to his familys' ruin. Claria likely didn't die like she originally did because she's named as Docs' beloved when he dies.
Corrupted Timeline-Old Biff goes back to make his younger self rich. Biff becomes one of the most powerful men in America destroying Hill Valley in his pursuit of power. Despite this it still takes him awhile to kill George. Doc is put in an insane asylum. Marty and Doc undo what older Biff did.
"The Second Corrected" timeline-The McFly family still retain the changes from the first corrected timeline. Doc save Claria and they wind up having a family instead of dying. Marty overcomes his berserk button "chicken" erasing the message Jennifer got from the future.