Vashti and Kuno are foils for each other in this story, meaning that their juxtaposition reveals important characteristics and qualities about them. While they love and value each other as mother and son, the two characters are different in a key way: Vashti is comfortable with her status quo life controlled by the Machine, while Kuno craves freedom from this restrictive form of technology.
Their relationship as foils becomes clear in passages like the following, in which Vashti reflects on her son’s rebellious nature:
She knew that he was fated. If he did not die today he would die tomorrow. There was not room for such a person in the world. And with her pity disgust mingled. She was ashamed at having borne such a son, she who had always been so respectable and so full of ideas. Was he really the little boy to whom she had taught the use of his stops and buttons, and to whom she had given his first lessons in the Book? The very hair that disfigured his lip showed that he was reverting to some savage type.
Here Vashti reflects with “pity” and “disgust” on how Kuno went from being “so respectable and so full of ideas” to “some savage type.” In having Vashti reject the non-conformist aspects of Kuno’s character, Forster helps readers understand her better as a character, demonstrating that she values being respectable and diligently reading the Book (the exhaustive user’s manual for the Machine). Likewise, Kuno’s later critique of his mother’s complacency teaches readers that he is not merely a “savage,” but a caring person who merely seeks human connection and a relationship with the natural world.