The whirligig’s mechanism, in which the wind causes its various parts to move one another, embodies the book’s central theme of cause-and-effect. Whirligigs further represent the far-reaching consequences of action by serving as catalysts for significant realizations for people Brent has never met and will in all likelihood never meet.

For each of these characters—Anthony, Jenny, Steph, and the unnamed narrator from Miami—the whirligig symbolizes something unique. For Anthony, it first stood for the pressure his mother put on him and then the release of that pressure. For Jenny, it is her grandmother’s teaching that there is good in people alongside the bad. Steph comes to associate the whirligig with the idea of unseen, illogical forces in the world. The man from Miami’s epiphany is that discord, as well as cooperation, are inherent to groups. By the end of the book, as he prepares to reenter society, Brent starts to view the whirligig as a metaphor for the interconnectedness of human beings across place and time:

He'd interlocked some of the propeller blades so that one would pass its motion to the others. In his mind, his whirligigs were meshed the same way, parts of a single coast-to-coast creation.