I'm getting tired of people explaining a lot of mysteries by claiming that "alternate timelines" or "time loops" are being created. What happened happened and can't happen any other way. I know that Faraday said there were variables, and he was exactly right. But do you know what he did then? He tried to change what he knew happened, and he died. It couldn't happen in the past, because that's not how it happened in the present. Every single action that the Losties have taken in the past has lined up perfectly with the present. That's what makes it fun to watch! If they were just changing things and creating "alternate timelines" we wouldn't get the cool "Oh, that's what that meant" feeling every episode.
The beauty of the whole thing is that they are changing the future! They're changing it into the present that we saw before they left; the present Locke, Sun, and the other 316 survivors are in. Think about it. If they had never travelled back to 1977, would Ben been have been shot? Would he have been taken to Richard? Would Ethan have been born? Would Amy have even been alive to get pregnant?
You might say "It would have happened anyway," but would it have? All we know is what did happen.
If "alternate timelines" could be created, nothing the Losties in the past did would affect the the 316 survivors on that beach. But you know what? Everything they have done, no matter how "reckless", has been exactly what we see in the present. The 316 survivors' mere presence on the beach proves that the actions that the Losties take will get everyone to the same place they've always been.
Now, do other "timelines" exist? Maybe. But the only timeline we have ever seen, and the only one we will ever see is the one that includes all of the events we've seen, heard or read about.
In short, Daniel Faraday was absolutely right. There are variables, and those variables completely change the equation. However, we already know how these variables work in this equation. -- 00:05, 4 May 2009 (UTC)