It is the slightly bizarre introduction of the alien presence of the Tralfamadorians that allows Vonnegut to discuss the central question of free will that operates in this novel. Tralfamadoreans have a curious way of looking at the world that incorporates the fourth dimension, allowing them to see all moments of time, both past, present and future, occupying simultaneously. This means that for them, free will does not exist, and they accept their fate, believing that since they can already see their future they are unable to change it. It is only on Earth that humans speak of the myth of free will, they argue, because humans mistakenly see time as a linear progression. Note what the Tralfamadorean says to Billy Pilgrim about the myth of free will at the end of Chapter 4:
I am a Tralfamadorean, seeing all time as you might see a stretch of the Rocky Mountains. All time is all time. It does not change. It does not lend itself to warnings or explanations. It simply is. Take it moment by moment, and you will find that we are all, as I've said before, bugs in amber.
However, even though Billy Pilgrim does seem to find his free will is curtailed throughout the novel, there is an interesting tension between free will and fate. Even whilst Vonnegut in Chapter 1 admits that all humans will die, supporting the forces of fate, at the same time he acknowledges that he has forbidden his sons to become involved in making weapons. However, overall, the fact that Billy Pilgrim, who is so badly trained and ill-equipped, survives the war when so many others better prepared for war, such as Ronald Weary, die, suggests that fate is the stronger force in the novel.