This is my first try at a theory.
Begin with an example. Ben's reaction to his daughter's death was shock. Why? Because Ben has obtained information about the future (at least up to a certain point - probably Season 6). He knows the stories of Jack, Kate, Hurley, Sawyer and Sayid and planned the construction of the landing strip for his Ajira flight (Kate and Sawyer's hard labor). He probably knows that he will be around at some point (someone will explain to him why he was shot). I think he also confirmed that his daughter lived up to a point in the future, which is why he thought he was not risking her life. What Ben did not count on was that one of the mechanisms for preserving the timeline, Smokey, could not intervene because Smokey was obstructed by the fence. His reaction was that "he broke the rules". Ben was not surprised that the mercenary (or Widmore) would chose to break an unspoken code but, rather, that the 'rules' could be broken at all. So he goes to the secret room and turns off the fence ! and allows Smokey in to the compound. Smokey immediately recognizes the risk to the timeline and harms the team but does not kill the leader. Why? Because Michael has to save Jin, who arrives on the Island in the future and ends up in 1977. Once Michael has done that, the mercenary can die.
So what is the Island? Think of the Twin Paradox. A twin leaves earth but will return to a twin that has aged more than it has. If a group were to leave Earth and return, they would want to ensure that they can return safely so they leave behind a hidden island that can move around earth in space and time. How do they ensure that they do not lose control of the Island? Give the island the capacity to cultivate a group of humans who are loyal to it (the hostiles, the French crew, Widmore, Eloise) who will speak a universal language (latin) and, give it a security system (Smokey) that protects the Island's location from being divulged (kill pilots, etc) and prevents other visitors from changing the timeline. People are manipulated in to loyalty and preserving the timeline through visions, etc.
My guess is that Richard's people left the Earth at some point and left the Island was left on its own. Dharma came along and threatened to overcome the Island's defense mechanisms (they can avoid Smokey and fight the hostiles to a draw) and started a time experiment with the Island itself. (Desmond hit the failsafe, there was a blue-shift and the Island will gradually return to the Earth's timeline but has not yet done so - see Rocket experiment)
Richard's people sent Richard back to save the Island. Richard never ages to the 815 people the same way they never age to Ben because he is periodically transported back in time. Richard is trying to find a leader that will work well with the Island to help it preserve itself. The Island gives Richard signals of who can help. First Richard used Ben but that failed (the incident did not stop the experiment), so Richard gives Locke something to indicate to Richard that Locke is special when he came back to 1954. He may now realize that the Island needs the guy with the book (Sawyer/Jacob) so that is why Richard is so disappointed when Locke chooses the knife. Richard/the Island chose wrong twice. So Kate, Hurley, Jack and Sayid have been brought back to help Sawyer. Theory by Tom
Begin with an example. Ben's reaction to his daughter's death was shock. Why? Because Ben has obtained information about the future (at least up to a certain point - probably Season 6). He knows the stories of Jack, Kate, Hurley, Sawyer and Sayid and planned the construction of the landing strip for his Ajira flight (Kate and Sawyer's hard labor). He probably knows that he will be around at some point (someone will explain to him why he was shot). I think he also confirmed that his daughter lived up to a point in the future, which is why he thought he was not risking her life. What Ben did not count on was that one of the mechanisms for preserving the timeline, Smokey, could not intervene because Smokey was obstructed by the fence. His reaction was that "he broke the rules". Ben was not surprised that the mercenary (or Widmore) would chose to break an unspoken code but, rather, that the 'rules' could be broken at all. So he goes to the secret room and turns off the fence ! and allows Smokey in to the compound. Smokey immediately recognizes the risk to the timeline and harms the team but does not kill the leader. Why? Because Michael has to save Jin, who arrives on the Island in the future and ends up in 1977. Once Michael has done that, the mercenary can die.
So what is the Island? Think of the Twin Paradox. A twin leaves earth but will return to a twin that has aged more than it has. If a group were to leave Earth and return, they would want to ensure that they can return safely so they leave behind a hidden island that can move around earth in space and time. How do they ensure that they do not lose control of the Island? Give the island the capacity to cultivate a group of humans who are loyal to it (the hostiles, the French crew, Widmore, Eloise) who will speak a universal language (latin) and, give it a security system (Smokey) that protects the Island's location from being divulged (kill pilots, etc) and prevents other visitors from changing the timeline. People are manipulated in to loyalty and preserving the timeline through visions, etc.
My guess is that Richard's people left the Earth at some point and left the Island was left on its own. Dharma came along and threatened to overcome the Island's defense mechanisms (they can avoid Smokey and fight the hostiles to a draw) and started a time experiment with the Island itself. (Desmond hit the failsafe, there was a blue-shift and the Island will gradually return to the Earth's timeline but has not yet done so - see Rocket experiment)
Richard's people sent Richard back to save the Island. Richard never ages to the 815 people the same way they never age to Ben because he is periodically transported back in time. Richard is trying to find a leader that will work well with the Island to help it preserve itself. The Island gives Richard signals of who can help. First Richard used Ben but that failed (the incident did not stop the experiment), so Richard gives Locke something to indicate to Richard that Locke is special when he came back to 1954. He may now realize that the Island needs the guy with the book (Sawyer/Jacob) so that is why Richard is so disappointed when Locke chooses the knife. Richard/the Island chose wrong twice. So Kate, Hurley, Jack and Sayid have been brought back to help Sawyer. Theory by Tom
