history changed - or not?

I was reading this post on b.la how today is the anniversary of the assassination of Robert F Kennedy; and I started thinking about strange unsolved stories. And then the vision of the terminator movie came into my brain and I thought, a standard science fiction plot is to foil a would-be assassin from killing someone instrumental in changing the world for the "good" of humanity. And then instantly my thought jumped tracks and I thought, what if the "good guys" failed and that instrumental person _is_ killed? Would it create a different parallel world? And then I thought, what if we are living in that time? You know, with all the world improvement GWB is doing.

It's an interesting idea to think about. It's not the first time I've thought about multiple parallel (or not so parallel) realities. I've found 4th and 5th dimensions explained as all possibilities existing. (Try to visualize that in all the nodal possibilities.) And then add the concept of time to each nodal possibility. And try to visualize _that_! Or, well don't. It's the same headache as someone in flatland trying to visualize my fingers typing on this keyboard.

It's all fun to think about, but ultimately useless to living in this reality. Or is it? If you believe in pre-destiny, this method explains all possibilities as known variables. If you believe in free-will, this method explains all possibilities of choice. Any choice is a pre-destined choice. Or is it? Is there a choice that is not predestined? (A bug, a non-standard behavior?) If you know all choices are predestined, including not making the choice, do you feel freer or trapped?Or something else?

Does knowing you have lived all the possibilities before (or concurrently) allow you the freedom to choose which choice you want to make in that exact moment in your exact reality - and not automatically choose the deepest groove.