The central theme of the novel is a question: whether a machine could ever be considered human. Yod the cyborg and Joseph the Golem are two artificial beings, brought to life in order to defend their communities, who begin to take on human qualities. This humanity is debated and questioned by the creators, the community, and the beings themselves.

Whereas Yod is a machine who slowly begins to discover his humanity, there are human characters who have slowly been turning their bodies into machines. In addition to the large amounts of cosmetic surgery that is conducted, humans receive implants and upgrades. Shira has a clock in the corner of her eye, for instance, while many characters have artificial organs or body parts that replace diseased or aged counterparts. Nili is the most extreme of these augmented humans, even to those in the world who are used to body augmentation. These augmentations have heightened her abilities and have reached the point where she is more machine than anyone else, but her quintessential humanity is never questioned. While Yod is a machine who seeks to be human, there are humans who have almost become machines.