Suppose that some time in the future, humankind figures out a way to make possible time travel into the past. Suppose, furthermore, that it turns out that the universe is holonomic - that is, there is only one past and one future and we can't change it (so we can't create an "alternative 1985" like in Back To The Future II). Effectively, the entire history of the universe would be predestined. So the going back in time would also be predestined. Anything that the time-travellers do while on their trip to the past would have already have happened and would always have happened. So we know that the time travellers cannot kill their past selves (or they would not be in there in the future to make the trip). In fact, anything that they do in the past must guarantee that the time travellers are alive and sufficiently healthy in the future to be able to make the trip back (which would not necessarily be the case if the time travellers were not there). So effectively, the time travellers would be their own guardian angels, "protecting" their past selves (deliberately or not) simply by the virtue of existing in the past.
Now, suppose that you are a future human in possession of a time machine. You don't worry about "responsible time travel" since you can't break anything or rewrite history. It's only natural for you to wonder just how far back in time you can go. With sufficient technological advancement, you might be able to go right back to the moment at the very beginning of the universe. And, just maybe by going back to that point in time you actually initiate the creation of the universe - you become God.
Sometimes I wonder if the universe is like that. But I suspect it is not - I find it very difficult to believe that free will is just an illusion.