Is Christian Shephard Alive?

Many people have theorized that Jack's dad, Christian Shephard, may yet be alive. In spite of the fact that Jack identified his father's body at the morgue, this theory is plausible because Jack found his father's coffin to be empty in the episode "White Rabbit." If the theory about Jack's dad being alive is true, this may explain why we were shown the story of Charlotte Malkin—as an allusion that Christian Shephard may yet be alive. This would also seem to explain why we keep seeing Christian in so many people's flashbacks; perhaps he has a more important role than we now know.