Well we deconstructed the sickness, electromagnetism, Ajira... it was only a matter of time until we addressed the big one, I suppose. Of course, this topic focus comes from the monumental finish to the last episode - where Sayid decides to shoot young Ben, thereby opening up a can of worms about what you can and can't do in time travel.
Let's briefly outline the H.G. Wells-y classical view, which Daniel Faraday appeared to share at the start of Season 5 when time travel was going crazy. In this account, one cannot go back in time and "change things" as such things would have already happened in your present if they were changed in the past. Time is, thus, considered a river or invariant timeline where changing things would affect your own future and so consequently mean you wouldn't go back in time in the first place (make sense?). Using the typical Hitler analogy - you can't go back in time to stop Hitler before what he did during WWII. This is because, if you did, not only would history change but so would your own time - so you therefore wouldn't go back to kill Hitler as Hitler no longer existed. Let's put it another way: in the Red Dwarf scenario. You can't go back and tell yourself to not do something - as if your past self avoided it, then he/she wouldn't go back again and say it - and so you couldn't have the memory of being warned by your future self, as for it to work your past self would later have to act as the future self in the conversation. This view is all about the cycle - one can theoretically go back in time to observe changes, or even make changes - but such changes have to have already happened in the traveller's world. So, for instance, the Losties could have been in the DHARMA Initiative, but they cannot affect what we already know occurred, e.g. the Purge (many people argue "why didn't the Others see that photo of Hurley et al in the 1977 DHARMA group shot at the Barracks - but for the moment we'll attribute that to an oversight - or should we not?)
Apologies for poorly articulating the standard time-travel theory anyway, for the majority of you will probably get it better than I do. But now we face the point of issue - how can Sayid shoot and kill a young Ben?! It could simply be "he's still alive, and it's that shooting that makes him so bitter and crazy", but I'm going to take a risk and gloss over that, though it would obviously completely solve the issue and negate this post entirely (fun!).
How can this happen? Are the Losties now in an alternate world, and do they now have the power to control the future - seemingly without any rules at all. This can't be true, as what would be the point of Faraday's warnings or Pierre Chang's comments at the start of the season that "there are rules". Faraday already broke them with Desmond - creating a sudden memory in Desmond's mind. Are the rules just going to be flung out of the window? What will happen to Ben now? It seems like Sayid has caused everything to now hit the fan, and will we see immediate consequences next week?
One can, unfortunately, only speculate what will happen when the rules have seemingly been broken. Are there any other time travel theories out there that you guys know of? What do you think will happen to "present" Ben now that little Ben has snuffed it? Let us know! And physicists among you be kind about this post's explanation of time travel - apparently everyone's an expert/critic these days!