Remember the old Mirror, Mirror Star Trek episode,where Kirk gets trapped in an alternate universe where the Federation and his crew are all "bad". Well this movie uses this basic idea to create a new Trek without destroying the old. Events at the beginning of the movie create an "alternate" reality where the characters are the same , but different at the same time with "old" Spock stuck here with "new" Spock. I applaud this idea because it gives thefuture movies and writers to do whatever they want, without worrying about some continuity glich. If they want to kill Sulu, for example, in the next movie, they can because we don't know what happens to the Sulu in this dimension.