[Tau Zero]

I've always thought that if you're going to time travel, then you have to cross into a parallel universe. In other words, you can't go back in your own time stream, but traveling into the past takes you to a parallel universe where the differences are to slight to notice. In that time stream you can do whatever you want to change their future and when you return, you return to the time stream your left. Whatever you did in the past to the "other" universe has no effect on yours.

In this case there is no paradox. I can go into the past, meet and kill my past self and return to my present. I would still exist, because in my time stream, i never died. In the other universe, i was killed.