was just talking with someone and we noticed how close the conversation between jacob and the other guy on the beach, and therefor the show in general mirrors the old testaments book of job.
god - jacob
lucifer - other guy
job - all the leaders on the island
lucifer is around at the begining but not at the same level as god. lucifer bets god that job is only happy and praising him because job is wealthy/content. god allows lucifer to take away from job but job continues to praise the lord (lord gives, lord takes away) dispite many difficulties. Although many profits proclaim to have spoken to god, very few do (enoch moses and mohamed, ect) and some pretend to as a way of holding onto power like ben. I see a lot of job in the character of locke with all the suffering in his life as well.
you can also tie in the battle in heaven first written by enoch and then re-examened and expanded into the lore we all know from miltons mid 17th century work paridise lost. Satan tried to over throw god and failed, was banished to the earth along with all the other angels who helped him for all eternity satan continuously tried to find ways back into heaven and hates god for banishing him.
so when they\'re on the beach and he says to jacob "you know how much I want to kill you" / lucifer is still trying to take over heaven but can\'t. however, in this story, lucifer maybe found a way by taking the image of another being, in this case the dead john locke?
Also, if the other guy can take the form of dead people, could he be jacks father and charlie, and all the other people that somehow pop up even though their dead time to time, like the devil taking the form of the snake to trick eve?
< /random thoughts>