In the very beginning (So It Begins) Christian sent the dog Vincent to find his son saying " he has work to do." Jacob said (in the Lighthouse) that Jack is here to do something and he needed to let Jack look out at the ocean to figure it out. In order to get him there he had Hurley say, "you have what it takes." This is the opposite of what Jack's father Christian told him in "White Rabbit." When Jack was a boy he got beat up by a bully and his dad said "you don't have what it takes to be a hero." Jack told Hurley he came to the island because he was broke and thought it could fix him. Jack has always tried to fix others as a doctor. At his wedding rehearsal Sarah called Jack a hero for "fixing" her. All of this is leading to an ending where Jack will be the hero. I think he will have a choice to make. Possibly between which of the two timelines to continue on. Jacob is all about free will and choices. Locke/MIB will try to influence his choice. The question will be whether Jack has the faith in himself to make the right choice. It will bring the series full circle from the beginning to end it with Jack as the hero. Jack's father on the island seems to have developed faith in his son to do the work needed but Jack has to find it within himself. That's the lesson and ties with the theme of Lost and finding oneself. Kind of obvious and anticlimatic BUT not really in that its been an epic struggle for Jack to get there and he has been his own nemesis at times.