In the beginning of season five’s finale, you see jacob and someone else (who we don’t know) talking. The other man claims that all that happens is “They come, fight, destroy, and corrupt.” Jacob replies with something about everything progresses (I’m really not sure). The other man is obviously talking about the people on the island. So if you think about it, he is basically saying that everything on the island keeps on repeating itself. Like a cycle of the events on the island happening over and over again. It starts with flight 815 crashing, then goes to everyone fighting and destroying the island, then the bomb. However, Jacob thinks that everytime this cycle takes place, something progresses. Maybe it’s the way the variables treat eachother or figure something out faster. Also, when Claire is having flashbacks to when Ethan took her in season two, she sees a mobile in the place where the others were going to keep Aaron. The mobile had oceanic planes instead of cute little bunny rabbits and stuff. The planes were also spinning in a circle. This is great symbolism that supports my theory! Don’t blame me if I get all of this wrong, I wasn’t allowed to watch LOST for the first four seasons (I was only seven). So know I playing catch-up and trying to watch seasons 1-4 by 2010!! Can the New year come any slower??