Desmond is Jacob who is the son of Horace. He was the only baby to be born on the island. While Horace was leading Dharma, he built the cabin for him, his wife, and his son. The son was named Jacob. During the purge, the baby is given to someone else in order to protect him. He leaves the island and gains a different name, Desmond Hume, just as others who left the island gained other names. Because he is special, he must return to the island because he was not supposed to leave. This is why he was sent on the sailing race and forced to stay inside the hatch. Sometime during the course of the time traveling events, Desmond becomes stuck between two times somehow, similar to when Locke saw Horace continually chopping down the tree. He is inside the cabin, which is also moving in time. This would explain why the cabin moves. I believe Desmond must reunite with Penny. Their love has been kept apart the entire show du! e to the island. When they reunite they will have altered the events of the past somehow, to save the island. I know this sounds a bit sketchy, but it is my first theory, so cut me some slack. Theory by Michael
