Privilege
Privilege—social status that grants an advantageous position over others—is among the most important themes in We Were Liars. Lockhart introduces the theme early with Cadence's description of her family as "athletic, tall, and handsome ... old-money Democrats" who summer "on a private island off the coast of Massachusetts." As people associated with the elite American culture of Martha's Vineyard and the Hamptons, the Sinclairs enjoy an economic and social status granted only to a select few. As a child, Cadence is blind to the privilege she has lucked into, understanding Beechwood as a magical place to spend her summers. But as Cadence grows up, her relative privilege becomes a point of conflict between her and Gat, who visits the island as a guest and not a member of the Sinclair family. Frustrated by Cadence's inability to see her own privilege, Gat points out to her that he has more in common with the non-rich staff on the island than with her family. When he mentions how he, Ginny, and Paulo are the only non-white people on Beechwood, Cadence asks who the others are, prompting Gat to punch his palm and express exasperation over how her privilege has prevented her from bothering to learn the names of the housekeeper and gardener. Ultimately, the Sinclairs' tendency not to recognize their privilege turns disastrous: Rather than appreciate what they have, the family members feud with each other over property, losing sight of the relationships that truly matter in their lives.
Inheritance
Inheritance—in both its literal and metaphorical senses—is another major theme in We Were Liars. The theme arises when Cadence states in her narration that as the eldest of the Sinclair grandchildren, she is the ostensible heir to her grandfather's island. While Harris attempts to treat his three daughters fairly by building each of them a house on Beechwood, later in life he becomes embittered and uses the inheritance of his fortune as a weapon. To express his displeasure at his daughters' life choices, Harris threatens to cut them out of his will and donate their would-be inheritance to Harvard. But beyond the estate to be inherited, Lockhart depicts how the Sinclairs inherit attitudes and behaviors. Like Harris, Cadence's mother is fixated on material wealth and refuses to show vulnerable emotions. When Cadence has her own strong feelings, she does her best to follow her mother's instructions and not express herself—a habit that leads to tragedy.
Manipulation
Manipulation—the influencing or controlling of other people through unscrupulous means—is a major theme in We Were Liars. Lockhart explores the theme most overtly—though not exclusively—through Harris, Cadence's grandfather. As the head of the Sinclair family, Harris has an outsized influence over the lives of his adult daughters. Disappointed in their failed marriages and continued reliance on the trust funds he set up for them, Harris punishes Carrie, Penny, and Bess by pitting them against each other for his affection. Harris's manipulation is at its most destructive when, during summer fifteen, he threatens to leave his money and land to Harvard, his alma mater. He also seeks to shame Penny for her husband walking out on her by telling Bess she can take over the Windemere house. However, behind Bess's back, he calls her a "grasping wench." Harris's abuse of his patriarchal authority prompts Cadence to try her own hand at controlling her family through unscrupulous means. In this way, Harris's manipulation precipitates the burning down of Clairmont, a tragedy that claims his grandchildren's lives.
Grief
Grief—deep sorrow caused by someone's death or departure—is a key theme in We Were Liars. Lockhart addresses the theme most overtly when Cadence's father leaves the family just before summer fifteen. From the lawn, Cadence watches him pull away in a car, and the abandonment makes her feel as though he has shot her in the chest. Her grief is doubled when her grandmother, Tipper, passes away around the same time. Upon return to Beechwood, Cadence's sense of grief is deepened even further when she learns that Gat has a girlfriend in the city. Although her feelings of despair cause her great suffering, Cadence follows her mother's lead and refuses to let anyone know what is troubling her. Cadence carries this inclination to avoid grief into the sections of the book that take place after the Clairmont fire. Rather than confront the reality of the accident, Cadence processes the loss of the Liars through a summer full of fantasy conversations with their ghosts, slowly coming to terms with what she has done.
Emotional Repression & Denial
Emotional repression—the tendency to push down one's feelings—is another crucial theme in We Were Liars. As with most other themes in the book, the denial of strong emotions is hinted at in the first chapter: "It doesn't matter if one of us is desperately, desperately in love," Cadence says. In this ironic statement, Cadence reveals that it does matter if she is desperately in love; however, she belongs to a family that pressures her into repressing how she feels. Lockhart explores the theme further through the behavior of Penny and Harris. When Penny's husband leaves, she demonstrates to Cadence her hard-willed ability to suck it up and move on, immediately redecorating the house to erase the memory of her unfaithful husband. Similarly, Harris shows a stubborn refusal to acknowledge the grief of losing his wife. When Cadence attempts to talk about how much she misses her grandmother, he simply says that the best part of him died with her and "that is all there is to say about it." Ultimately, the Sinclair family's repression may help them retain dignity and pride by protecting them from exposing any vulnerabilities. However, repression is simultaneously harmful because it isolates them in their feelings, ensuring that they never have a chance to process their grief.
Trauma
As the invisible, unacknowledged force driving the story, trauma is among the most important themes in We Were Liars. Lockhart establishes the theme in the opening chapter when Cadence alludes to her family's tendency to push away unpleasant realities: "It doesn’t matter if divorce shreds the muscles of our hearts so that they will hardly beat without a struggle." Trauma and the psychological wounds it leaves behind arise again when Cadence recalls the shot-in-the-heart feeling of watching her father drive off to begin a new life without her and her mother. Later in the novel, Cadence is diagnosed with post-traumatic migraines following her "accident" on Beechwood. It takes the remainder of the story for Cadence to come to terms with the gruesome reality of the fire, which is so traumatic that she develops dissociative amnesia to avoid remembering it.
Addiction
Addiction is another major theme in We Were Liars. Lockhart explores addiction less overtly than other themes, depicting it as an insidious presence in the lives of the book's characters. The theme arises early in Cadence's narration when she lists the ostensible virtues of the superficially perfect Sinclair family: "No one is an addict." The irony of Cadence's pronouncement becomes clear later in the novel. In fact, her mother and aunts are heavy drinkers who use alcohol as an excuse to move past inhibitions and treat each other as enemies. Lockhart also explores the theme through Cadence's reliance on Percocet pain medication following her "accident." More than a physical pain reliever, Percocet helps Cadence dissociate from grief and other difficult emotions.
