In the book John desperately wants to avoid going to Vietnam. In order to ensure safety from the draft, he amputates his own finger. In doing so he cuts himself off from the rest of the people his age who are going to war. He begins to feel alienated and this eventually leads
to him to move to Canada.
Another example of amputation in the book is the armadillo. Owen took the armadillo's claws when Johnny gave it to him in order to illustrate how God had used his hands to be the instrument of Johnny's mother's death. At first Johnny was baffled at why Owen had taken the claws. He and Dan thought about it for a long while and then it finally dawned on Dan what Owen was doing.
Yet another example of John Irving's obsession with amputation takes place in the final chapter of the book. When Owen uses "The Shot" in order to save the Vietnamese children from a grenade, his arms are blown clean off from the elbows down. When this event happened Owen's nightmare was finally realized, though not in the way he expected. He had seen himself saving Vietnamese children and dying from it but he had not imagined it would be in the Phoenix airport.
John Irving uses amputation as an underlying motif throughout his book. The purpose of this is to have a religious meaning. He wanted to show that through God, even a person who is missing a part of themselves, is still whole. Irving brilliantly merged a fascinating and engaging story with a thought proving subtext.