In last nights episode Hugo got a visit from a very familiar face. Charlie seems to either be alive and well or Hurley is being haunted by his best friends image as he seems to keep trying to tell Hurley to return to the island which would bring anyone to madness if you knew they had been long dead.

So obviously that got me thinking about Jack's own mental deteriation seen in last seasons finale, where a very unstable Jack desperately wants to get back to the island and even makes a comment to the doctor "why don't you bring my father down here and we'll see whos more drunk". Seems to me like more than one "ghost" is making the rounds to the Oceanic 6, because after Jacks little visit to Hugo, something durastic must have changed his mind to want to get back to the island, and I can't think of a much better motivator than a dead father breathing down your neck telling you to get back ;) .

Well refering to the other thread, it would seem that Jacks dad is this mysterious Jacob. Therefore he may just be alive, with Jacobs spirit or something. So it may not be the exact same situation as Hurleys.