Jack is Jacob?
Of course. Here’s some (circumstantial) evidence, broken down by category, and in no particular order:
Character analysis: Jack is wiley and is playing Ben for a fool. Jack of the kidney sac bait-n-switch. Jack of the “I know the Others are coming, but I’m not going to tell you until I have a plan.” Jack of the “Ben, you’re my ally – until Locke gets here.”
Character and story analysis: Jacob almost surely is someone we know. If Jacob is just Jacob, why introduce a new and important character more than 75 percent of the way through your story? Because you don’t. We’ve already been introduced to Jacob. He was the first person we ever saw.
Character and story analysis: The man of science and the man of faith must come together to save the island. (They’re the yin and yang, after all). Think about it ... Jack and Locke have a contentious relationship. Locke has pleaded for Jack’s help throughout the series. “Jack don’t do this.” “Jack, you’re not supposed to do this.” And so forth. Isn’t it time for Jack to ask for Locke’s help? Oh wait, he already did, when he was a time-leaping phantom named Jacob (trapped in a time-shifting cabin no less).
Symbolic: Jack is the son of Christian Shepherd (a Christian shepherd?), which might suggest that he's a messianic figure. Perhaps at the end of the series Jack seemingly sacrifices his life to save his friends (and the island and the world).
Symbolic: As a messianic and mythic figure, Jack must sacrifice himself and be reborn. Once Jacob can leave the cabin, who wants to bet that an older, exhausted Jack steps out the door? Sort of like another character whose name begins with a “J” stepped out of a tomb after he was dead.
Suggestive: If you needed help, who would you enlist? Family, right? Who has Jacob enlisted? Christian and Claire Shepherd. Jack's father and half-sister. Ben even says, at one point, "What wouldn’t a father do for his son?" Why wouldn’t Christian help his time-leaping, trapped, foolish son?
Suggestive: What does Christian Shepherd hand to Jack in the webisode “The Watch.” A watch. Hmmm, time references?
Suggestive: Jacob’s eye is brown.
Jack’s eyes? Brown.
Suggestive: Jack is not on Jacob’s list.[/b] We don’t know what the list is, per se. But why put yourself on your own list?
Suggestive: Room 23 indoctrination. "Only fools are enslaved by time and space." Suggests that someone is enslaved by time and space. Most likely character? Jacob. And who has been our biggest “fool” (in that he’s tried to fix things, but has only made things worse, time and again)? Jack.
Suggestive: Jack’s tattoo. Translation, “he who walks among us, but is not one of us." What’s the one character that is among all others on the Island, but does not commune with anyone? Jacob.
Suggestive: Tattoo artist’s insight into Jack. She can peer into your soul and tell you your true identity (there's a clue there – why is she discerning Jack's "true identity" in the first place?). She refers to Jack as "a great man, a leader." Now, how does Mikhail describe his "leader" to John? He calls him a "magnificent man". Or better, there’s Ben. How does Ben describe Jacob? "The man in charge—he's a great man, John, a brilliant man."
Suggestive: Jack’s books in his office (from “A Tale of Two Cities”
:
Fire in the Mind: Faith and the Search for Order, Pale Horse Coming, Redemption, Valhalla Rising (in which Dirk Pitt discovers he has twin 23-year-old children raised by another – a love who he assumed was dead – if those aren't Lost themes, what are?),
No Place Like Home (a Mary Higgins Clark title that plays off “The Wizard of Oz”
, and my favorite
Prisoner of Azkaban (in which the vile and terrifying Sirius Black turns out to be the heroic godparent of Harry Potter, imprisoned by the forces of evil, eventually freed to help battle the forces of evil – Sounds like Jacob could be Sirius Black.)