Introduction: Warning, there will be a spoiler or two from prior seasons as I go along. So, if you are watching 24 out of order, I may ruin it for you. Though, if you are watching 24 out of order, the show will ruin it for you anyway...
Long term fans of 24 know that not only Jack's life changed when his wife died at the end of season one, but frankly, the way he viewed the world and his job changed. Jack has become significantly more self destructive and he rarely views his own life with any real worth. He is in many ways trying desperately to join his wife and end the terrible pain that her death has caused him. It's for this reason that he always seems to take the path of most resistance. That's because it is a path for which he sees little to lose. He has become beholden mostly to the mission at hand and little else. Furthermore, he treats those that get in the way of his mission with as little care as he often treats his own life when executing a mission.
The only time that Jack strays from this very cold and yet very calculating philosophy is when it involves his own family. He showed an uncharacteristic humanity in working against CTU when they attempted to use his nephew as a pawn in the sixth season. Furthermore, he has always tried to do everything to protect his daughter. Yet, that's the only time when his humanity comes out. When faced with a choice between saving the life of love interest's former husband Paul Raines and a witness, he put a gun to doctor's heads to force them to save the witness.
In many ways, Jack actually shows a deeper humanity. He sees past the human being in front of him and to all the faceless and nameless human beings that would suffer if his mission is not accomplished. In this way, he is the ultimate spy. He has a laser light focus on the mission at hand. Yet, it is the internal conflict that has become the central theme of this season. All of his draconian and heavy handed tactics have become second nature to him. When he needed to get information from a corrupt Secret Service agent, he "naturally" suggested that the agent's family be kidnapped and used as leverage. Now, he turned Ebaku's unwitting girlfriend into an asset and a double agent.
While all of this comes naturally to Jack, it is anything but natural to the FBI agent Renee Walker. The only thing more horrifying to her than having to try and kidnap a wife and child is that the whole process is oh so natural to Jack. She wants Jack to show the same kind of humanity because his lack of humanity is what's most frightening to her. Everyone that questions Jack's methods constantly alludes to the death of his wife, but none of them seem to get it. It was her death that took all of that away. He got it back only fleetingly when he fell in love with Audrey Raines, but in the end, Jack's own humanity died with his wife. He has resigned to a life of pain. He has resigned to being driven solely by patriotic duty, myopic duty to mission, and his own life and humanity are things he sacrificed long ago when he held his dead wife at the end of the first season.
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