Slaughterhouse-Five explores Fate and Free Will and the illogical nature of human beings. Protagonist Billy Pilgrim is unstuck in time, randomly experiencing the events of his life, with no idea of what part he next will visit (re-live) — so, his life does not end with death; he re-lives his death, before its time, an experience often mingled with his other experiences.
Billy Pilgrim says there is no free will; an assertion confirmed by a Tralfamadorian, who says, "I've visited thirty-one inhabited planets in the universe . . . Only on Earth is there any talk of free will". The story's central conceit: most of humanity is inconsequential; they do what they do, because they must.
To the Tralfamadorians, everything simultaneously exists, therefore, everyone is always alive. They, too, have wars and suffer tragedies (they destroy the universe whilst testing spaceship fuels), but, when Billy asks what they do about wars, they reply that they simply ignore them. The Tralfamadorians counter Vonnegut's true theme: life, as a human being, only is enjoyable with unknowns. Tralfamadorians do not make choices about what they do, but have power only over what they think (the subject of Timequake). As the Narrator, Mr Vonnegut believes this theory, expounded in chapter one, "that writing an anti-war book is like writing an anti-glacier book", since both will always exist, and are both equally difficult to stop. This concept is difficult for Billy to accept, at first.
Author Vonnegut's other novels, e.g. The Sirens of Titan, suggest that the Tralfamadorians, in Slaughterhouse-Five, satirize Fatalism. The Tralfamadorians represent the belief in war as inevitable. In their hapless destruction of the universe, Vonnegut does not sympathize with their philosophy. To human beings, Vonnegut says, ignoring a war is unacceptable when we have free will.This human illogicality appears in the climax that occurs, not with the Dresden fire bombing, but with the summary execution of a man who committed a petty theft. Amid all that horror, death, and destruction, time is taken to punish one man. Yet, the time is taken, and Vonnegut takes the outside opinion of the bird asking, "Poo-tee-weet?" The same birdsong ends the novel God Bless You, Mr. Rosewater, as the protagonist gives away his fortune to the plaintiffs of hundreds of false paternity suits brought against him — a Dada observation of human absurdity