When Marty decides to go back from 1958 to 1988 in Back to the Future, he decides to go back several minutes before the doctor is killed by the terrorists, to warn him.
But when he arrives late, he sees another copy of him re-enacting what had happened at that point of time.
How can this make any sense? Shouldn't the other copy be extinct? or at least not present at that place at that time?
For the sake of argument, if that copy's existence is justified, does that mean that he (the copy) will do the same actions done by the "real Marty" and perhaps take the same decisions to come back early and warn the doctor?
Wouldn't that cause an infinite cycle of Marty clones?