With Season 5's introduction of time travel to the world of Lost then the show's plot dynamic is under scrutiny. Darlton set their stall out when they talked up how much time and research they put into breaking down the time travel aspects. They've explicitly stated that there is one timeline on the show, and have used the likes of Pierre Chang and Daniel Faraday, right from the first episode of the new season, to express that there are strict 'rules' that cannot be changed.
When Pierre Chang told the Dharma worker about time travel the worker's reaction was to wonder whether they were going to go back in time and kill Hitler. Chang jumped down the guy's throat and told him that could not be done because of the rules. Likewise, when Sawyer wanted to go stomping into The Swan Station and get beer he was informed, in no uncertain terms by Faraday, that he was wasting his time.
You can't change the past. What happened, happened. There's only one timeline and you can't create divergent timelines. Those are the rules.
Apart from Desmond, these rules have (so far as Jughead) been adhered to perfectly well. (There are debates about this, of course, to do with Locke meeting Ethan and so on, but personally I feel there has been nothing to contravene the fundamental principle that the past cannot be changed, and has not been changed, and the Losties happening to be in it is presenting no infringement - it's just filling in the blanks.)
Then there's Desmond and this 'memory insert' business. Now this does trouble me. Not enough to cry foul just yet - because Faraday has reached a conclusion that Desmond is unique. It'll probably be 'explained' by Desmond having had dalliances with time travel already; it's flimsy, but Lost can just about wing this notion and make it fly.
So what am I talking about here then, you ask? Ostensibly I am talking about cyclical paradoxes created by time travel. It’s about Locke, Richard Alpert, and a compass. Let's take a deep breath. Clear our minds. And try and get this straight as painlessly as possible.
Let me walk you through this, using the compass as a prime example. The cyclical paradox goes as follows:
In 2005 (for argument sake, since we don't actually know the precise year), Locke is lying by the drug plane, shot in the leg. Richard Alpert turns up, tends to the wound, and gives Locke a compass. Locke takes this compass back to 1954, and meets Alpert, and gives him the compass. Alpert keeps the compass, therefore, so that in 2005 he can give it to Locke. And so it goes.
The obvious question this flow presents is: Where did the compass come from? Here's a diagram I artfully put together. (Click on it to enlarge.)
Amazing graphics, I know. Thanks. But what the flow demonstrates is the closed circuit of the compass handover; the important part is that the compass comes from nowhere. Locke can't give it to Alpert if Alpert hasn't been given it from Locke. You with me? The compass has no start point, and this is a cyclical paradox. Something from nothing. Well, it would be, but I can get around it by theorising there are two compasses for a little while, and one of them gets lost in the loop.
Here's an elaboration of the flow diagram to explain the point. (Click on it to enlarge.)
Basically, then, Alpert already had a compass before Locke turned up in the 1950s. This makes sense. A man turning up, claiming to be from the future, having an identical compass he apparently got from a future counterpart would convince Alpert that Locke was genuine. So, in this respect, the compass doesn't present a paradox - with a bit of creative thinking.
So, are we OK? We clear? Because I want you to have both feet planted firmly on the ground, assured, for the introduction of the next bit: How Locke and Alpert meeting makes for a (so far) irresolvable cyclical paradox.
Let's run it through again. How did Alpert know to find Locke by the drug plane, injured, and give him a compass so that 1950s Alpert would know him? Because Locke, in 1950, turned up and presented a compass? That can't work. Because how did Locke know he had to present a compass? Because Alpert told him so! You see the problem? The actual knowledge that a compass was required to facilitate a meeting came out of nowhere. Something from nothing.
It's precisely the same idea as the compass example I outlined, only we could get around that by saying Alpert already had a compass in his possession. We can't say that Alpert already had the idea he would need to give Locke a compass in the future beforehand. Here's another diagram illustrating the closed loop. (Click on it to - oh, you know by now.)
An example. You are where you are now and some guy shows up wearing a crown and furs, rich as can be. He gives you lottery numbers and a time machine and tells you to go back in time, find him, and tell him to play those numbers. So you do it. You go back in time. You find the man, looking all poor and raggedy, and give him lottery numbers. Then you return to your own time.
The use of the winning lottery numbers to make a poor man rich is precisely the same impossibility as Alpert’s use of the compass to make Locke prove he was from the future.
(I know for some people that this time travel logic just doesn't sit well with their brains. It's fair enough. I have a similar problem with drawing pictures, as my flow diagrams show - my brain just can't grasp it.) The fact of the matter is there is, at this moment, an unresolved cyclical paradox in the show. You can take my word for it if that works better for you!
My worry is they'll never even attempt to explain it.
My worry is they haven't even realised the error of their logic and will go on to do more of the same, passing this off as ‘clever’ storytelling and ingenious use of their new-found time-travelling Island dynamic.
Hopefully, for some of you, your eyes will be opened to this problematic way of considering time travel and you'll be alert and on the lookout for such events in the future. In the meantime, for the philosophical amongst you, we're left with this. . .