Determinism - the theory that all choices are pre-determined by circumstance. Knowledge of the paticular circumstance would change the outcome of your "choice".
So, basically, if we believed this idea then we, as humans, would have no real control over what happened in our lives, merely an illusion of choice. In essence, it could support the idea of destiny - inevitable choices that lead us to an inevitable outcome, an inevitable path that we must follow.
To be honest, I'm not sure if I like this idea or not really. It's certainly impossible to say for definite that it is false, but then there's no real proof that it's true either. I mean, the thought of just following a set path in life has it's attractive points - you could never really make a 'wrong choice' because you were meant to do what you did and it's comforting to think that everyone is going somewhere in life.
But then, how is it decided who gets what destiny? How is the choice made that gives one person fame and fortune and another poverty and misery? I suppose life can never be fair but I find it hard to believe that some people are unable to work their way out of a bad situation simply because some higher power has determined that they can't.
I guess, I'm still a fan of choosing your own way in the world - although, that too could be a choice in itself. Can you choose to make your own choices? And if that's the case, then was that choice pre-determined and so you're still not really acting independently?
I can just tell, two years of Philosophy and TOK is gonna make my head hurt....