There are a ton of people disputing the whole "Whatever Happened, Happened" aspect of Lost's time travel. So, my theory about why whatever happened did happen and how changing the future is difficult to the point of being, as Daniel said, impossible.
Basically, picture the Losties as being at point A in time, in 1977. Picture 2004, when they crashed, as being point Z. The characters have little to no knowledge of what points B through Y are, how they led to point Z, and what the outcome should be in order to change it. Because they dont know any of this stuff, they could act on something, believing they are changing the future, and in fact end up causing the future.
Think about it. Aside from knowing about the Purge, the Losties have no idea what to do to make the future different, aside from maybe killing Ben as a child. Isnt it likely that their attempts to kill him may in fact drive him to turn against DHARMA as a whole, rather than just his father, and become what he is in the future?
Daniel may know more about the past than any of the others (possibly Juliet as well), but still knows that his knowledge and motivations are the same as they always were, and because of this he will act in ways that ended up causing the future that the Losties came from. If none of them know exactly what they did to cause point Z, then it is nigh-impossible to change it. They wouldnt know what they were changing because they dont know what happened. While the 1970's is point A for them, it is just a small part of the Islands history, and it always happened the same way, with them a part of it.
Knowledge of the future may be a key part of Lost, such as Ben and Widmore's seeming omniscience, but the past always happened this way. We are just seeing it for the first time. Theory by Smoke & Mirrors
Basically, picture the Losties as being at point A in time, in 1977. Picture 2004, when they crashed, as being point Z. The characters have little to no knowledge of what points B through Y are, how they led to point Z, and what the outcome should be in order to change it. Because they dont know any of this stuff, they could act on something, believing they are changing the future, and in fact end up causing the future.
Think about it. Aside from knowing about the Purge, the Losties have no idea what to do to make the future different, aside from maybe killing Ben as a child. Isnt it likely that their attempts to kill him may in fact drive him to turn against DHARMA as a whole, rather than just his father, and become what he is in the future?
Daniel may know more about the past than any of the others (possibly Juliet as well), but still knows that his knowledge and motivations are the same as they always were, and because of this he will act in ways that ended up causing the future that the Losties came from. If none of them know exactly what they did to cause point Z, then it is nigh-impossible to change it. They wouldnt know what they were changing because they dont know what happened. While the 1970's is point A for them, it is just a small part of the Islands history, and it always happened the same way, with them a part of it.
Knowledge of the future may be a key part of Lost, such as Ben and Widmore's seeming omniscience, but the past always happened this way. We are just seeing it for the first time. Theory by Smoke & Mirrors
