Meat and the Animal Body
In an effort to divorce herself from all instances of human violence, Yeong-hye abstains from eating meat. She recalls all of the flesh she has consumed over the course of her lifetime in a gory and visceral way. The nightmares that plague her seed a different notion of sanity and reality, one in which Yeong-hye resolves to transform into a plant. Yeong-hye's steadfast refusal to meet the needs of her animal body drive her closer to death.
Although Han has stated in interviews that "this novel isn’t a singular indictment of the Korean patriarchy," readers will notice the ways in which men policed Yeong-hye's body, contributing to her mental state. For example, Mr. Cheong's treatment of his wife ranges from forcefully grabbing her arm to raping her. Yeong-hye also reveals that her father regularly beat her during her childhood. At their family lunch, Mr. Kim tries to force Yeong-hye to eat meat, which culminates in her attempting to commit suicide.
Agency and Belonging
Witnessing Yeong-hye attempt to enact her agency by transgressing social constraints awakens In-hye to the knowledge that her life has never truly belonged to her. In-hye always carried on through the sheer force of her will. As described in Part 3, "her devotion to doing things the right way had been unflagging, all her success had depended on it, and she would have gone on like that indefinitely." However, her ordered life came to a shattering halt after her husband made the erotic film of himself and Yeong-hye. The way forward becomes precarious for In-hye even as she continues parenting her son and running her business.
In-hye locates the body as a site for (what should be) agency when she says, "It's your body, you can treat it how you please. The only area where you're free to do just as you like" (Part 3). However, she recognizes that her sister's attempt to claim agency over her body ironically will end her life.
Defiance
Yeong-hye defies societal conventions by adopting a vegan diet. While vegetarianism and veganism may exist in small pockets, overall it is shown to be highly unusual when Mr. Cheong's colleagues and Yeong-hye's family scrutinize her choice. The family lunch scene in particular showcases Yeong-hye's dissent turning violently toward herself as she tries to commit suicide.
Ultimately, Yeong-hye wishes to defy the violence she feels is inherent to human nature. She does so by rejecting her animal body and focusing her efforts on metamorphosing into a plant. Yeong-hye's veganism escalates into a full-on rejection of food. This logic situates her in a different reality that in fact brings her closer to death due to starvation. Even as her physical strength dwindles, Yeong-hye actively resists the medical staff multiple times.
Nausea and Physical Disgust
One symptom that Yeong-hye suffers from throughout the novel is intense disgust and nausea towards human bodies (belonging to herself and others) and the violence they are capable of. This provokes her decision to abstain from eating meat. Yeong-hye's nightmares about flesh and violence overtake her and disrupt biological processes such as eating and sleeping, as well as her sex drive. She avoids having sex with her husband because his body "smells of meat," but Mr. Cheong enacts the violence that Yeong-hye so desperately attempts to avoid when he rapes her (Part 1). In Yeong-hye's mind, she undergoes a transformation by becoming a plant, ultimately rejecting human bodies. This shows how tortured Yeong-hye feels at the embodiment inherent to the human condition. This experience of nausea in response to the human condition can be found throughout literary history, but Han weaves this existentialism into the context of violence and patriarchy.
Violence
Physical and psychological violence casually pervade the novel. In the beginning of Part 1, Mr. Cheong makes several statements that reveal how both he and Mr. Kim have and continue to use force to bend Yeong-hye to their wills. In Mr. Cheong's case, this ranges in severity from squeezing his wife's wrist to raping her. According to Yeong-hye, her father physically beat her during her childhood. All of this family violence comes to a crescendo at the ill-fated lunch where Mr. Kim stuffs a piece of pork into Yeong-hye's unwilling mouth. Yeong-hye then directs the violence inward when she attempts to commit suicide.
Being hospitalized does not put an end to the violence that Yeong-hye experiences. The medical staff often treat her with unnecessary brutality. In-hye intervenes when the doctors try to insert a feeding tube into Yeong-hye against her will even if it will mean saving her life.
The Uncanny
In literature, the uncanny refers to a process of defamiliarization: when something familiar is presented in a strange and unsettling way. Han primarily relies on surreal imagery and dream communication to evoke this eerie atmosphere whilst making psychological and social commentary. In Part 1, for example, Yeong-hye's dream monologues describe "hazy distinctions, boundaries wearing thin. Familiarity bleeds into strangeness, certainty becomes impossible." This worsens as the novel progresses.
Perhaps the starkest example of the uncanny in The Vegetarian occurs in Part 3 when In-hye has a sickening sense of déjà-vu. At the hospital, Yeong-hye tells In-hye "I wanted flowers to bloom from my crotch, so I spread my legs, I spread them wide," echoing nearly word for word what In-hye heard Yeong-hye say in a dream. Here, In-hye potentially flits across the border of different realities as she connects with Yeong-hye in her psychosis.
Social Pressure, Constraints, and Conformity
In the beginning of the novel, Mr. Cheong considers Yeong-hye to be an average and unassuming housewife. The only unusual trait she exhibits is her refusal to wear a bra as it physically constrains her. Mr. Cheong wakes one morning to find his wife discarding all their meat and animal products, and Yeong-hye begins to chafe against social constraints in earnest. Even at an important company dinner with Mr. Cheong's colleagues, Yeong-hye refuses to conform to conventional behavior. She sits (braless), staring openly at the others as they enjoy their meat dishes and discuss the strangeness of vegetarian diets. Only Mr. Cheong suffers from the shame of losing face.
At another meal (this time with the rest of the Kim family), social rules also come into question when Mr. Kim reacts violently toward his daughter's refusal to eat meat. Everyone takes it in stride when Mr. Kim verbally and physically assaults his daughter, and they even blame Yeong-hye for provoking her father's anger in the first place. In-hye is the only one to stand up to her father when he tries to force Yeong-hye to eat meat.
Part 2, "Mongolian Mark," deals with the consequences of transgressing social boundaries. In-hye's husband acts on his obsession with Yeong-hye by painting flowers on their bodies and making an erotic film. While In-hye calls emergency services, she later reflects on how she likely would have crossed some kind of social line if her husband and sister had not done so first.
Yeong-hye's determination to transform herself into a plant leaves In-hye feeling angry and abandoned by her sister for "[shucking] off social constraints." This wakes In-hye's understanding that she is imprisoned in a life that never belonged to her. While both men and women suffer from social pressures, this novel deals more closely with those that women specifically face.