Billy had a framed prayer on his office wall which expressed his method for keeping going, even though he was unenthusiastic about living. A lot of patients who saw the prayer on Billy’s wall told him that it helped them to keep going, too. It went like this: “God grant me the serenity to accept the things I cannot change, courage to change the things I can, and wisdom always to tell the difference.” Among the things Billy Pilgrim could not change were the past, the present, and the future.
This passage occurs in Chapter 3, after Billy has been kidnapped and taken to Tralfamadore in 1968. There he sees the same inscription on a locket around the neck of Montana Wildhack, the actress brought to mate with Billy in the Tralfamadorian zoo. The saying brings to light the central conflict of Billy’s attempt to live a Tralfamadorian life in a human world: he subscribes to the Tralfamadorian belief that there is a fourth dimension of time and that time is cyclical, but he lives in a world in which everyone believes that time moves in a single, linear progression. Tralfamadorians would argue that humans never know the difference between the things they cannot change because there is no difference; nothing is negotiable in a universe of predefined, structured moments.