Nothing in this book is true.
Live by the foma that make you brave and kind and healthy and happy.
The Book of Bokonon 1:5
At first glance, this epigraph seems unnecessary. Of course Cat's Cradle isn't true. That's why the nice bookseller shelved it in the fiction section. And the world hasn't ended in an ice-nine apocalypse, so there's that too.
The epigraph's actual purpose is to introduce one of the story's major themes. As we'll learn, foma is the Bokononist word for lies, so Bokonon's argument is that certain lies will "make you brave and kind and healthy and happy." The epigraph is asking you to look for value in the lies that brings those qualities to your life—whether those lies are religion, love, or, just maybe, even this book of fiction.
It also suggests that the opposite might be true. Maybe the truth actually makes us cowardly, mean-spirited, weak, and unhappy. There's only one way to find out: you'll have to explore the novel itself.
Or you can just check out our "Themes" section.