Irony

Chapter 5 heavily explores the issue of free will.  As Billy spends more time with the Tralfamadorians, he starts to understand their concept on free will and appreciates their theory.  They think that no matter what you do, you can not stop the natural order of things, and that basically, everyone in the world is playing in a massive play that is out of their control.  What is ironic is it is Billy's desire to share with the world his belief that we have no choice over our actions.  It is his own free will that drives him to teach the world his theory about how we cannot do what we want in the world.