Silas and Sally Phelps are Tom Sawyer's aunt and uncle, and deceptively warm-hearted people. They are loving and welcoming toward both Huck, whom they believe to be their nephew, and Tom, supposedly a perfect stranger but their true nephew in actuality. Sally is especially protective of the boys and falls into hysterics whenever she thinks something bad has happened to them. Huck reflects that in his time with her, Sally "mothered [him] so good." However, despite the kindness they show Huck and Tom, the Phelpses are racist plantation owners who keep hundreds of slaves, and hold Jim captive on their property so that they can return him to his owner. Additionally, when Huck lies about a boat-related accident, Sally questions if anyone got hurt. When he replies that a Black man was killed, Sally is relieved and exclaims, "Well, it’s lucky; because sometimes people do get hurt," indicating that she does not see Black people as human. Twain uses the Phelpses to explore the ironies of Southern hospitality. They are gracious hosts to white people who come to their door while simultaneously enslaving hundreds of Black men and women whose lives they consistently devalue. They keep Jim chained in a shed and plan to return him to the person who has enslaved him, but consider themselves absolved because they visit the shed to pray with him. They even unchain and celebrate Jim after he has helped nurse Tom back to health, but remain fundamentally unchanged as people.

Through these characters, Twain explores the concept of moral absurdity. Along his journey, Huck consistently meets people, like Sally and Silas, who seem superficially kind and good-hearted. However, a closer look reveals how immoral and corrupt these seemingly good people truly are. In an upside-down, immoral world, petty crimes like a local drunkard's empty threats are punishable by death while slave owners like the Phelpses go unpunished. They get to continue on with their lives of affluence and status. Evidently, the adult society surrounding Huck, the one that adults in his life have urged him to embrace, is governed by a disarrayed collection of corrupt and contradictory rules that disregard logic and justice and disproportionately penalize the powerless. In a world that enslaves human lives, morality is an impossibility.