Vincent is a manifestation of the island and in the last 10 minutes of the finale healed Jack. As I find it difficult to believe that Kate waited to step it up a notch, and go "Bam" like Emeril, finally, she did. I also find it hard to believe Jack would let MIB stab him. I've seen the island heal far worse wounds. It's easier to accept an open ending, as in "Cowboy Bebop", Jack could merely be resting, why should we accept a dark ending? MIB dies, Jack lives on to fight another day. Either way, that show ruled. Most thought provoking, edge of your seat, intense shows ever on Television. It will be missed.