The island is The Monster's prison, and The Others are The Guards by Ricardus Alpert

"LA X" has provided us with quite a bit of information on The Others' society, and The Temple. It has also provided us with quite a bit of information on The Monster with the revelation that not only is it The Man in Black, but that he wants to "Go Home." Given that information, I believe that The Others' purpose is more complex than defending the island. Since I believe that MIB is imprisoned, with Jacob as his jailer, I believe that The Others' are the Prison Guards. Their true purpose is to prevent The Monster's escape from the island, by any means.

Given the reaction of Dogen and his crew to Jacob's death, I think Jacob was the only thing that kept MIB in check. With him gone, MIB can do whatever he wants. But why were they afraid that MIB would head for The Temple? Because I believe a Mechanism for leaving the island lies inside it. Richard and Jacob have been leaving the island for quite some time, and it couldn't have been due to the Frozen Donkey Wheel because they wouldn't have been able to come back. The Others have a mechanism for leaving, and they guard it in The Temple. MIB plans to use it in order to "Go Home."


But is it really such a bad thing? I believe it's very much so. I think MIB has been trapped on the island because he's a threat to the outside world. I'd go as far as to say the catastrophe that Jacob has been working to prevent is MIB's escape from the island. Once he's free, "Every single one of us is Dead."