Making Your Own Choices?

So a few nights ago a good friend and I got to debating the simple question of the meaning of life.  Of course, thing quickly got heated and eventually progressed to the deeper question of whether life is predestined or we have the right to choose.  Though I'm still not sure what I think, my preferred choice of freedom of choice was challenged by my friend's faith in determinism.

Determinism is a complex theory that, in a very rough summary, says choice is just a fragment of our imagination, and what we hold to be choices are actually results of prior states of affairs.  So in a roundabout way, our choices are merely results of previous things, we only think we choose them.  It is a complex theory, so to better understand it I would suggest checking out this website. 

Perhaps a picture best describes it.

The prior decisions act as a machine in which the effect is shown under the illusion of choice.

The only way I was able to even somewhat wrap my mind around this idea was to think of Alphonse and how his choices were not really his own.  He believed he was making choices considering the actions of others, but, in actuality, his "choices" were all predetermined responses to the calculated actions of others to have him "choose" the response, even though it was previously determined.  Our choices are not actually choices, but are really necessary consequences of prior "choices," which were really effects of previous events, and so on.

My struggle with this theory is where did this start?  Determinism differs from predestination in that "choices" are a result of previous, whereas, with predestination, "choices" have been made for us by a greater power, but still can be more than just a calculated and necessary response to the previous.  But with determinism, what was the original "previous?"  Originally someone had to make a choice so that the was a triggering event to start the necessary chain of reactions.  I also find it hard to believe that choices are just necessary responses, because while I do believe that you can predict someone's decision based on outside influences, I think humans are far too complex for their mental capacity to be a simple response without any look to the future.

I do believe this theory places a new spin on my approach to The Tale and the question of predestination I'm addressing in my final project.