John Locke is a man of faith, but his faith is a blind one. He really doesn't know anything about the Island and it's secrets, has never met Jacob exactly, doesn't know what the Monster is, can't explain the space-time oddities, has never been to the Temple, et cetera. In short, he believes he's serving a higher purpose and will take orders from those he believes can guide him in this purpose. But what, exactly, that purpose is, he's as Lost as everyone else.
The Others seems to share in John's devotion to the Island and it's secrets. But the Others know a great deal John does not. Ben said he didn't know what the Monster is, but he knows and speaks with Jacob. Richard Alpert is clearly a man who knows a thing or two about the Island, as do Charles Widmore and Eloise Hawking. They are all Others, but they are not united in their cause. There is clearly a "Rift" among the Others, with Ben on one side and Widmore on the other.
So far, Locke has received most of the very little information he has about the Island from Ben, some from Richard, and some esoteric and vague guidance from Christian Shepard. What happens when Locke starts to get information about the Island from the "other" Others? What happens when he gets a different take on what's going on? What happens when Widmore and Hawking start telling Locke a thing or two about the Island?
Something happened that Widmore and Hawking left the Island. In the case of Widmore, he wants very badly to get the Island back, going so far as to kill for it. Indeed, he even told Ben the Island was taken from him, and that it did in fact "belong" to him. Will the events that shaped this Rift cause Locke to question or lose his faith in the Island? Will he come to see himself as a pawn in a game, like Desmond has?