The central philosophical theme in The Lower Depths explores the tension between the value of truth and the allure of comforting falsehoods. The character Luka, a pilgrim, embodies the idea that people often require lies to protect themselves from life's harsh truths. He first illustrates this belief by soothing the dying Anna with promises of peace after death. Although his later discussions with Bubnoff and Pepel imply he may not genuinely believe in an afterlife, he remains committed to offering solace to those in distress. Throughout Acts II and III, Luka provides hope to downtrodden characters through potentially unfounded reassurances. For example, he tells Nastiah that he believes her love story, despite its obvious fabrication, to spare her feelings. Similarly, he suggests to the Actor that he can overcome his alcoholism at a free clinic in an unnamed town if he resolves to change. This encouragement leads the Actor to make some progress and briefly recite poetry as he once did. Likewise, Nastiah finds comfort in Luka's support, and Anna passes away more peacefully than she might have otherwise. However, when Luka leaves, taking his comforting stories with him, the characters feel more despondent than before his arrival.

Throughout the play, various characters challenge Luka's comforting deceptions. When he consoles Anna, Pepel questions whether Luka believes his own words. Bubnoff, Kleshtch, and Medviedeff also confront Luka, but Sahtin most thoroughly represents his opposition, advocating for truth. For much of the first three acts, Sahtin serves as a background voice of skepticism and realism, exemplified at the end of Act II when he remarks, "The dead hear not. The dead feel not." In Act IV, however, he takes center stage with three monologues about the significance of truth for humanity. While he recognizes Luka's compassionate intentions, he does not champion compassion himself. Instead, he asserts, "The lie is the religion of the servant and master... the truth is the inheritance of free men!" He continues to praise human potential and the pursuit of truth. The contrast between Sahtin's idealistic humanism centered on truth and the human need for empathy and compassion forms the play's central conflict.

The motif of life in the lower depths as akin to a prison or hell is a recurring theme throughout the text. The title clearly hints at this, as these scenes from Russian life explore the dark, concealed, and buried facets of existence. The phrase "lower depths," as opposed to heights or celestial realms, naturally conjures images of hell due to its underground connotations, and the miserable lives of the inhabitants strengthen this association. The absence of light further symbolizes the dark side or hell. This is reflected in the lack of meaningful work or progress, illustrated by Kleshtch’s futile attempts to fix a lock that can never be repaired. In Acts II and IV, Bubnoff and Krivoi Zoba sing about being trapped, never seeing the sunrise or sunset, setting a grim tone for life in this underground setting. Even in Act III, which occurs outdoors, a brick wall is described as obstructing "the heavens," highlighting the oppressive atmosphere. The lack of private space, with benches and bunks serving as beds, heightens the prison-like imagery. Various characters in the play talk about escaping this life, as if they are serving a sentence. Anna views death as a release from her suffering, Kleshtch anticipates her death to free him from the boardinghouse, and Natasha dreams of being rescued by someone. Ultimately, none of the characters find liberation except through death, and two even end up in prison. Kleshtch becomes even more ensnared in the lower depths...