The tone of As I Lay Dying varies depending on which character is narrating, since all of them have different motivations and outlooks on life. Of the core family group (with the exception of Vardaman), all of the book's narrators are a bit cynical and distrustful of others. Their narrations are mired in skepticism and reservations about the good intentions of other people—and even about themselves at times. The family are pariahs in Jefferson, and the guardedness this causes is ever-present in the text.
The family members are even suspicious of one another. In Chapter 4, Jewel explains that he believes Cash's construction of the coffin is an act of showmanship rather than one of a dutiful son:
It’s because he stays out there, right under the window, hammering and sawing on that goddamn box. Where she’s got to see him. Where every breath she draws is full of his knocking and sawing where she can see him saying See. See what a good one I am making for you. I told him to go somewhere else. I said Good God do you want to see her in it.
Each narrator is somewhat uncertain of themselves, and this uncertainty is also reflected in the tone, whether characters outright second-guess themselves or make attempts to justify and further elaborate their perspectives. When Dewey Dell shakes Vardaman in Chapter 14, she thinks, "Maybe I couldn’t stop them [her hands]. I didn’t know they could shake so hard. They shake both of us, shaking." Here, Dewey Dell gives the impression that she was unaware of her own strength and suggests that she may not be at fault for the shaking, since it seems she had no control over her actions at the time.