Fire
Fire resurfaces frequently as a theme in The Glass Castle. As Jeannette suspects, it follow her around, becoming a fixture in her life. The very first, and perhaps most pivotal fire inspires Jeannette's first memory, of being burned while cooking hot dogs at the age of three. Though she suffers extreme injuries, fire becomes a fixation for Jeannette, who cannot keep herself from playing with it and watching it. The work contains a number of other fires that claim houses, sheds, and injure other characters. It can be said to represent a trend of chaos that is both natural and staged by man. The theme of fire relates closely to other themes concerning nature and pollution that also appear in the memoir.
Bended Joshua Tree
The tree that Rose Mary spots in the desert is indicative of the effect the struggles of life have on each of the characters in the memoir. Constantly blown by wind, the Joshua tree grows sideways, not upwards and, as Rose Mary declares, becomes beautiful because of its struggle. The Walls children can be seen as individual Joshua trees, their lives shaped by the constantly blowing wind of their parents' frequent moves and questionable habits. Jeannette tries to resist this force at first when living in New York. She does not want anyone to know about her past or judge her for allowing her parents to remain homeless. However, her attempts to grow upwards despite the constantly blowing wind are averted and she eventually succumbs like the Joshua tree, and grows sideways, finally allowing her struggle to be heard.
Mountain Goat
Rex's nickname for his favorite child. The nickname refers to Jeannette's endurance in face of trouble. Like a mountain goat, she is able to climb mountains without losing her footing. Jeannette is the only child given a nickname by her father. The endearment implies a special relationship between her and her father that the other children could not share with Rex. Additionally, the nickname foreshadows Jeannette's persistence and endurance when she realizes that her and her siblings must live apart from their parents if they are to ever lead stable, fulfilling lives.
"Perversion of Nature"
Especially during the time they spend in the desert, the Walls place a huge emphasis on nature being corrupted by man. Even the most natural scenes are often interrupted by a structure that would not be there but for the needs of man. When Brian and Jeannette run into the lettuce field after scaring away the bullies, they are sprayed by pesticide. Not knowing (or perhaps not caring) the two continue to frolic and rejoice in the field. Again, during their play Brian and Jeannette encounter hazardous and toxic waste in the dump. The presence of this man-made material amidst nature creates dangerous, almost fatal circumstances for the two. While Rose Mary and Rex definitely see some of these products of technological civilization as a "perversion of nature", like the irrigation in Battle Mountain, Jeannette does not always remember it that way. Indeed, often the "perversions" like the pesticide and toxic waste add a bit of magic and adventure to her memories. Only presently do the circumstances appear particularly dangerous.
"Boundary Between Turbulence and Order"
Rex describes this concept of physics after Brian and Jeannette almost die in a fire they set while playing with toxic waste. He warns them that no rules exist in the Boundary between turbulence and order and that if they do, nobody yet understands them. That day he says they have gotten too close to the boundary. In a way, the Walls children live in perpetual proximity to this boundary. After Rex begins drinking heavily and there is no food in the house, they begin scavenging for food and clothing through various means and enter into a place where rules and order no longer exist. The Boundary reappears at the end of the novel when Jeannette remarks that the flame of the candle is bordering the boundary between turbulence and order. This suggests a relation between this boundary and the ever-present fires of the novel; both represent chaos and control throughout the work.
Self Sufficiency
Even during their hardest times, Rex and Rose Mary Walls refuse to become charity cases. They do not even accept help from their children in their late adulthood. The value of being self sufficient descends mainly from Rose Mary Walls, whose upbringing in an incredibly disciplined home leads her to forgo the rules when she becomes a mother. Her children, she insists, must learn how to be self sufficient and strong. They should not rely on society or doctors or anything else to help them through life. Even when they fall ill or injure themselves, Rose Mary prefers to treat the wound at home rather than cater to what she considers a false need to visit the hospital. Though the Walls value self sufficiency they are not always able to maintain it, and sometimes their methods are not sufficient for survival at all.
Nonconformity
Rex and Rose Mary Walls also insist that their children are special and that they need not conform to the societal norm. Rex is even a little saddened when his son Brian joins the Air Force, what Rex considers "the gestapo." Nonconformity also impacts the elder Walls' relation to authority. Neither of them is capable of taking orders from authority very well. Rex gets into arguments and fights with bosses and law enforcement, and Rose Mary struggles to conform to the idea of a teaching job. She prefers the carefree and self-defined life as an artist, which does not force her to conform to another person's style or schedule beside her own.
The Glass Castle
The title of the book and a major theme within it, the Glass Castle represents Rex's hope for a magical, fantastic life in which he can provide for his family and please his children. Rex lays out plans for the Glass Castle, including detailed dimensions for each of the children's rooms, but he never actually builds the castle. For a long time Jeannette believes that he will but she gives up on the hope after the hole they dig for the foundation of the Glass Castle is filled with garbage. Though the physical structure is not erected, the symbol the Glass Castle represents remains with Jeannette in her childhood and helps her to believe that her father will do what he promises. When she discovers that this is not always true and realizes that the Glass Castle will never actually be built, she has reached adulthood.
