The concept of determinism examines the idea that humans lack free will and that external forces outside their control shape their lives. In The Pigman, Zindel explores the idea of determinism versus free will through all the main characters and poses the question of whether the characters are responsible for their fates or if they are imprisoned by circumstances limiting or impeding their ability to choose differently. Through the recurring motif of locks and cages, the author enforces the idea that every person in the story is physically or emotionally trapped. Angelo Pignati’s grief over his lost wife has made him a prisoner in his own home. His denial of her death chains him to a cycle of mourning and grief, preventing him from engaging with reality. It is fitting he befriends Bobo the baboon, a wild creature held against his nature in a locked enclosure, and their relationship is a sad symbol of the human condition.

Lorraine is a prisoner in her home, locked in by her mother’s fear of the outside world’s corrupting influence on her daughter, which results in controlling, abusive parenting tactics. Lorraine is hesitant to visit the zoo with John and Mr. Pignati because seeing the animals in cages unsettles her.