A prisoner of his own mind

Billy Pilgrim's status of mental stability has been subject to dispute for perhaps as long as the history of SH5 itself.  Those arguing that Billy has lost his sanity due to Post-Traumatic Stress Disorder claim that his episodes of warping through time are just symptoms of his disease.  This standpoint allows to say that Billy is a prisoner of his own mind.  Because his mind has been twisted and is no longer capable of logical thinking or processing events normally, Billy is incapable of living in a chronologically accurate fashion.  Pilgrim's PTSD defines the order in which Billy experiences moments of his life.  PTSD strips all sense of normalcy from Billy's life, which could be the cause of Billy's loneliness and feelings of being different.  Both of these feelings are apparent from Billy's lack of ability to form lasting, meaningful relationships.  In this sense, PTSD defines not only how Billy will interpret events from his life, but it also severely inhibits the possibility for Billy to really connect with someone.

As Billy's mind has been taken hostage by his controlling PTSD, his life has slipped out of his grasp.  Billy ironically claims to believe in free-will, while he is powerless to even the order in which he experiences his life.  Billy complains often towards the end of his life of feeling lonely, and being unhappy with his life.  In this area Billy has no one to blame but himself.  If Billy is a believer of free-will, he should not feel that he is powerless to change his life to benefit himself.

 When Billy accepts his fate, especially in his knowledge of when he will die, Billy changes his belief of free-will to one of fate.  While earlier I have thought that SH5 shows no advancement of plot or character development, I must now admit that I was wrong.  Billy Pilgrim shows growth, although not in a properly linear sense that is familiar.  Billy Pilgrim's growth is harder to identify because it is a change in his beliefs, a change in his way of thinking.  Billy's growth is the change of his understanding of life, in that he once believed in free-will, and after his visit with the Tralfamadorians and the war Billy has instead become  a believer in fate.  Billy's belief in fate disallows him making positive changes in his life, and truly enjoying all that life has to offer.

 The power of positive thought is often underestimated.  If you are unhappy with something in your life, only you have the ability to change the situation or at the very least, your perspective.