We can assume that The Lighthouse has the names of people Jacob sought to bring to the Island for his own reasons (candidate or progress to further his situation) From what we have seen Jacob touched various characters & that seemed to create their destiny to reach the Island, these touched characters also became candidates (NOTE apart from Kate from what we saw on the cave walls) (this includes characters such as Boone, Shannon etc just we didn't see their flash-backs to what happened, other characters who died were crossed off the cave list) How come Hurley only got touched upon his second arrival to the Island (Ajira flights with the guitar case) & only after leaving the Island became a Candidate?