Modernism has come to be identified with a few specific stylistic methods and a few over-arching themes. Faulkner’s As I Lay Dying exemplifies the hallmarks of modernism in both of these areas as the work utilizes a stream-of-consciousness style (informed by the popularity of psychoanalysis) and takes up themes of social fracture and an unraveling of a previously stable social fabric.

Style and theme, in As I Lay Dying, work together to reinforce a central conceit regarding social fracture and fragmentation.

This is a story about a single family, yet it is also the story of many minds. While each character in the Bundren family is responding to the same death, they each react differently. The style of the novel makes the psychological differences between the characters exceptionally clear.

Faulkner chooses to take on the mental voice of each character, depicting the internal life of Vardaman as being in stark contrast to that of Cash, which is in turn in stark contrast to Darl or Dewey Dell’s mental landscape. Thus the style of stream-of-consciousness expresses the notion that even within a single family there are vast differences of emotion and perception.

By the end of the novel, the family is literally broken up when Darl is committed to a mental health facility. When a new woman is brought in to take Addie’s place as the Bundren matriarch, the family’s dissolution seems complete. They are no longer the family they were at the outset of their journey.

Also notable here is the fact that a fragmentation within the family is reflected in the fragmentation of the story (told from varying points of view).

"Faulkner demonstrates how there are many ways of looking at and interpreting history. It is necessary to consider all views, to synthesize them, and to arrive at a more complete picture." (eNotes)

Social fragmentation is closely associated with ideas of change and a sense of weakening ties to a stable past. (This is especially true for Faulkner, but we can see the fixation on “historical shift” (and a resulting internal turmoil on an individual level) in the work of Dos Passos, Hemingway, Eliot and Woolf as well. In the work of those writers, too, stylistic choices resonate with the theme of fragmentation, isolation and instability in various ways.

The characters in As I Lay Dying are importantly linked to ideas of weakening historical ties. This is the core of Addie’s character in the novel, as she reflects bitterly on her experiences and finally insists on being buried back home, returned to an existential and emotional place of integrity—a place where she was whole and may have felt continuous with a sense of history.

In leaving home, she suffers from the break. She is never repaired.

Darl broods on his own existential drift at times. 

“In a strange room you must empty yourself for sleep. And before you are emptied for sleep, what are you. And when you are emptied for sleep, you are not. And when you are filled with sleep, you never were. I don't know what I am. I don't know if I am or not. Jewel knows he is, because he does not know that he does not know whether he is or not. He cannot empty himself for sleep because he is not what he is and he is what he is not.”

Connections to a known past or to a sense of origins are essential to a stable identity. Darl is sent away to a mental health facility in part, it would seem, because he is brought to the point of believing, “I don’t know what I am.”