In As I Lay Dying (and The Sound and the Fury as well), Faulkner uses an experimental free-style narration to reveal multiple consciousnesses and shifts in time and space. The novel is comprised of 59 narrations by 15 narrators, all of which, therefore, become unreliable as they contradict each other. In short, Faulkner makes the reader decide who is telling the truth, if any. In this way, Faulkner says there is no fixed, objective truth. Instead, we only have the voices of many truths conflicted.
Faulkner's style juxtaposes Hemingway's as the two dominant styles of the American modernist movement. Whereas Hemingway is plain, tough, macho, straightforward, and journalistically trustworthy to a fault (he distrusts adjectives), Faulkner is much more a mix of many styles, as he buries his voice among other, competing ones. Hemingway may seem more trustworthy on a surface level, but many critics "believe" Faulkner more simply because he wants his readers to intuit truths subjectively.
Faulkner shows the intense subjectivity of modern consciousness much like a cubist painter approaches his subject. Instead of revealing his subject wholistically and chronologically, Faulkner shows fragmented pieces arranged episodically, often out of order. For example, Addie's character speaks from the dead. Faulkner seems to be saying that the sum of his characters' parts are as important, if not more so, than the whole.
Faulkner believes his characters are not limited to time and space, even after death (the past is never past; everything lives on). There are psychic time shifts. For example, Darl knows his mother is dead even though he is not present at her deathbed. Darl can also telepathize with Dewey Dell, much like identical twins can. By doing so, Faulkner legitimizes the Psychoanalytic and Archetypal approaches to explaining abnormal behavior by posing the questions: "Can we ever escape the past?"; "Do ever know what is objectively true?"; "What happens to the mind after the body dies, doesn't it live on?"; "How do we really know who's crazy; isn't it what people think of you that makes it so?"
By presenting multiple points of view in circular form, Faulkner achieves a daring kind of fiction that shows many wills conflicted. So says Enotes:
Through these varying perspectives, the reader witnesses both the events that take place and the character's individual perceptions of them. Indeed, at times the reader can only discern events by comparing information from various narrators. The reader learns about the assumptions and peculiarities of the different narrators, as well as their social and religious environment. As a result, Faulkner constructs not only a rendition of events but also a series of interconnected psychological studies.