Faulkner often uses stream of consciousness as a literary device in the novel. As a motif, this technique helps emphasize the disconnect between characters' internal experience and the world outside of them. One example occurs in Chapter 1, when Armistid drops Lena off in town:
[H]e watched his tongue seek words, thinking quiet and swift, thought fleeing A man. All men. He will pass up a hundred chances to do good for one chance to meddle where meddling is not wanted. He will overlook and fail to see chances, opportunities, for riches and fame and welldoing, and even sometimes for evil. But he wont fail to see a chance to meddle Then his tongue found words, he listening, perhaps with the same astonishment that she did: “Only I wouldn’t set too much store by…….store in …” thinking She is not listening [...]
Armistid and Lena do not exchange very many words. Outwardly, Armistid seems like a quiet person who does not have much to say. Between clipped pieces of dialogue, however, Faulkner delves into Armistid's stream of consciousness. His thoughts are not all complete, but they give the reader the sense that he has some real anxieties on Lena's behalf that he is refusing to say out loud to her. For all she knows, this man has shown her some simple kindness and will never think about her again.
Armistid is not a major character. Still, Faulkner highlights the mismatch between his inner reality and the outer world. It is not so much that Armistid's feelings are of major consequence to the novel. Rather, his stream of consciousness draws attention to the fact that even a passing stranger has a head full of thoughts, memories, and beliefs nobody will ever know about. Every character in the novel is far more complicated than the other characters want them to be. The stream of consciousness motif invites the reader to notice moments when characters are failing to understand one another.
In Chapter 20, Hightower descends into fraught reminiscence; Faulkner occasionally interrupts Hightower's stream of consciousness with an extended metaphor comparing the man's thoughts to a sticking wheel on a vehicle that is racing toward something. By the end of the chapter, the wheel has come off:
The wheel, released, seems to rush on with a long sighing sound. He sits motionless in its aftermath, in his cooling sweat, while the sweat pours and pours. The wheel whirls on. It is going fast and smooth now, because it is freed now of burden, of vehicle, axle, all.
This metaphor helps Faulkner express how memory and forward-moving reality grate against one another. Hightower is the vehicle careening along toward something. What that something is, neither he nor the reader is quite sure. Optimistically, it is a future where he has a coherent narrative to tell himself about the Civil War, racism, and the generational trauma in which his family has played a part. As he ages, this coherent narrative disappears over the horizon. The only thing he is surely moving toward is death, passing by further incomprehensible scenes of injustice along the way.
At the same time, the vehicle representing Hightower is composed of multiple parts. If the body of the vehicle is Hightower's living, aging body, it moves along its path by way of wheels. At least one of the wheels explicitly stands in for Hightower's thinking. His thoughts carry him along his life path. The problem is that, as the stream of consciousness in this chapter reveals, Hightower's thinking is always circling around the past: he dwells on his childhood, his young adulthood, and even his grandfather's death years before he was born. His body has no choice but to travel forward on the road toward the future, but the wheel of his thinking is always trying to take him off the road.
Faulkner mentions a third part of the wheel, the axle, which strains to hold the wheel on. In the extended metaphor, the axle is the part of Hightower's mind that tries to hold everything together so that he can be a composed member of society. When the wheel of his thinking veers off into the past, this part of him tries to correct course and bring his thinking back to the present. During the stream of consciousness in this chapter, the axle comes under enormous strain. At first when Hightower sinks deep into reminiscence, the whole vehicle slows down as the wheel wobbles and sticks. It is as though while Hightower is consumed by memory, he stops moving so fast through time. However, the strain eventually overtakes the axle's ability to hold the wheel on. In this passage, the wheel of thinking finally comes off. Hightower's thinking begins wheeling free, the whole vehicle discomposed. It is not clear whether Hightower is dying in this passage, whether he is having some kind of temporary reverie, or whether he has lost his mind entirely. What is clear is that the novel leaves Hightower at a moment when he has given up making sense of his memories and has simply surrendered to the feelings and internal experiences they evoke.