Jack's Lack of a Backround

Though this subject has been discussed many times, I am still kind of hung up about it. One thing I was thinking about is how maybe Jack's own self-image is not strong. Sometimes, it can be so difficult to see oneself, and I know that at times I will either get a compliment or someone will say something about my character that surprises me. Maybe Jack's vagueness is to demonstrate that he is unsure of who he is, and he has difficulty seeing himself. This trip is in a time of loss, so maybe he just feels that he has been left alone, and is unsure of who he is without his wife.