If time travel is possible then our actions are predetermined.
Let's start with time. Time moves in a solid direction at a constant pace. No object within time can move to next Tuesday any faster than any other object in time can. In the physical world however, a being can move towards a finish line at a faster speed than another being. One can even move away from the finish line if he or she chooses. You're free to go left, right, up, down, front-wards, back-wards or any other direction you choose. You have choice. Our actions are only bound by science and physics.
It seems that time itself is the element which allows us to move freely in our world. If you could take the "constant element" away from time, and perhaps, stop time altogether, all of our actions would stop. Every being and every thing within time would be frozen at the exact nanosecond that time was stopped. You couldn't possibly believe that you could make the wind stop blowing, or the Earth stop rotating, while you were still free to move within space, could you?
While watching a DVD, if you hit the pause button, the actors will freeze and everything will come to a halt until you decide to hit play again. Once you hit play, they pick up right where they left off. Let's pretend you could take you're remote control and give it to one of the actors within whatever show you're watching. Let's say that actor hit the pause button. He, as well as his colleagues would be stuck for eternity from that moment forward, UNLESS an outside entity from a dimension other than that television show were to intervene. No one within the show could save the day, obviously, since our hero froze them all. That analogy is a little unfair, given the fact that a television show has a proven, predetermined ending. However, the same applies to the real world. If you had a way to stop time, you should first be able to step outside the dimension that time is grappling before stopping or changing its momentum or direction, or you'll become a victim of your actions.
If you could travel to the future, then there would have to be a future that will be played out as time takes it toll. Not an unknown future, but a PREDETERMINED future which is written in stone. Without that predetermination, how can you leap forward to a time and place of multiple endings? A land where you may have died on every single day at every possible second. If you could go to the future there would have to be a future that was laid out. Where some things happened and others didn't. This is where I come up with the notion that if time travel is possible then our actions are predetermined.